Patent Application
20060039937
The present invention relates to a composition having antioxidant properties, and to the preparation and use thereof.
An example of an area of application of the compositions according to the invention is cosmetics. The object of care cosmetics is wherever possible to obtain the impression of youthful skin. In principle, there are various ways of achieving this object. For example, existing skin damage, such as irregular pigmentation or the development of wrinkles, can be compensated for by covering powders or creams. Another approach is to protect the skin against environmental influences which lead to permanent damage and thus ageing of the skin. The idea is therefore to intervene in a preventative manner and thus to delay the ageing process. One example of this is the UV filters already mentioned, which, as a result of absorption of certain wavelength ranges, prevent or at least reduce skin damage. Whereas in the case of UV filters the damaging event, the UV radiation, is screened off by the skin, another route involves attempting to support the skin's natural defence or repair mechanisms against the damaging event. Finally, a further approach involves compensating for the weakening defence functions of the skin against harmful influences with increasing age by externally supplying substances which are able to replace this diminishing defence or repair function. For example, the skin has the ability to scavenge free radicals formed by external or internal stress factors. This ability diminishes with increasing age, causing the ageing process to accelerate with increasing age.
A certain degree of tanning of the skin is regarded in modern society as attractive and as an expression of vigour and sportiness. In addition to this desired action of the sun on the skin, a number of undesired side effects occur, such as sunburn or premature skin ageing and wrinkling. Of particular importance here is the wavelength range from 280 to 400 nm. This range covers UV-B rays having a wavelength of between 280 and 320 nm, which play a crucial role in the formation of solar erythema, and also UV-A rays having a wavelength of between 320 and 400 nm, which tan the skin, but also allow ageing, favour the triggering of an erythematous reaction or can exacerbate this reaction in certain people or even trigger phototoxic or photoallergic and irritative reactions.
Skin damage is not caused just by sunlight, but also by other external influences, such as cold or heat. Furthermore, the skin undergoes natural ageing, with the formation of wrinkles and a reduction in the elasticity of the skin.
A further difficulty in the preparation of cosmetics is that active ingredients which are intended to be incorporated into cosmetic compositions are frequently unstable and can be damaged in the composition. The damage may be caused, for example, by a reaction with atmospheric oxygen or by absorption of UV rays. The molecules damaged in this way may, for example, change their colour and/or lose their activity through their structural change.
A known way of dealing with the problems described consists in adding antioxidants to the compositions.
According to CD Römpp Chemie Lexikon [CD Römpp Lexicon of Chemistry]—Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995, antioxidants are compounds which inhibit or prevent undesired changes in the substances to be protected caused by the action of oxygen, inter alia oxidative processes. Areas of application are, for example, in plastics and rubber for protection against ageing; in fats for protection against rancidity, in oils, cattle feeds, automotive gasoline and jet fuels for protection against gumming, in transformer and turbine oil against sludge formation, and in flavours against odour impairment. Compounds that are effective as antioxidants are, inter alia, phenols, hydroquinones, pyrocatechols and aromatic amines which are substituted by sterically hindering groups, and metal complexes thereof. According to Römpp, the action of the antioxidants usually consists in that they act as free-radical scavengers for the free radicals which arise during autoxidation.
However, there continues to be a demand for skin-tolerated antioxidants which are also suitable for use in skin-care and/or skin-lightening compositions.
The object of the invention is therefore to provide a composition which has a skin-lightening action and/or a protective action against UV rays and/or exerts a protective action against oxidative stress on body cells and/or counters skin ageing.
Surprisingly, it has been found that certain esters of ascorbic acid with benzoic acid derivatives are eminently suitable for achieving the abovementioned object. The present invention therefore relates firstly to a composition having antioxidant properties comprising at least one compound of the formula I or a cosmetically, dermatologically or pharmacologically tolerated salt or derivative thereof
where R1 to R4 can be identical or different and are selected from
Advantages of the compositions according to the invention here are, in particular, the antioxidant action and the good tolerability, in particular skin tolerability. In addition, the compounds described here are preferably colourless or have only a weak colour and thus only result in slight discoloration of the compositions, or none at all.
Thus, the compounds of the formula I to be employed in accordance with the invention are, for example, highly suitable for the replacement of butylhydroxytoluene (BHT) in compositions.
In particular, the hydroxybenzoic acid esters exhibit excellent water solubility, it also being possible specifically to obtain amphiphilic or oil-soluble compounds via additional esterification using fatty acids. Particular preference is therefore given to compounds in which at least one of the radicals R1 to R4 is a gallic acid radical and preferably another of the radicals R1 to R4 is a C12-24-fatty acid radical.
The compounds of the formula I can be incorporated into compositions in a simple manner, where, in particular, the substantial pH-independence of the composition proves advantageous in practice.
In addition, the compounds of the formula I have a positive effect on the stability of the compositions comprising them, in particular to increased temperature and separation.
Also of advantage is the particular action profile of the compounds to be employed in accordance with the invention, which is evident in the DPPH assay (see below) in a high anti-free-radical efficiency (AE).
The present invention therefore also relates to the use of the compounds of the formula I, as indicated above, as antioxidants having a rapid action or for the preparation of a composition having antioxidant properties.
In addition, preferred compounds of the formula I combine antioxidative properties with UV absorption in the UV-B range in the molecule.
Furthermore, compositions according to the invention inhibit tyrosinase activity and are therefore also suitable as skin-lightening compositions.
The use of physical mixtures of ascorbic acid or derivatives thereof with gallic acid or derivatives thereof is known from the literature:
Only little literature exists on the gallic acid esters of ascorbic acid: L-ascorbyl 6-O-gallate, L-ascorbyl 6-O-(3,4-dihydroxybenzoate) and L-ascorbyl 5-O-gallate are disclosed in Gan, L., Seib, P. A., J. Carbohydrate Chemistry, 1998, 17(3), 397-404. The 5- or 6-esterified compounds are formed in the mixture in the esterification of ascorbic acid using gallic acid in concentrated sulfuric acid, where it is described that L-ascorbyl 6-O-gallate can be purified by fractional crystallisation. Furthermore, the publication describes the mutual conversion of the 5- or 6-esterified compounds in solution. The suitability of the compounds as antioxidant is likewise investigated: in the test described, it is found that L-ascorbyl 6-O-gallate is less effective than propyl gallate, but more effective than L-ascorbic acid or L-ascorbyl palmitate.
European patent application EP-A-1 145 710 discloses ascorbic acid derivatives which are stabilised compared with vitamin C and which promote the synthesis of epidermal ceramides, which improve the skin barrier function, the appearance of the skin and its moisture content and are suitable for the treatment of dermatitis. These are ascorbic acid derivatives which, in the 2-position, either carry a sugar radical or are esterified by means of an alkyl, aryl or alkylaryl acid, preferably ferulic acid. The 5-O- and 6-O-positions here can optionally additionally be etherified or esterified in the manner mentioned. Examples of suitable ascorbic acid esters which are mentioned are ascorbyl 2-cinnamate and ascorbyl 2-ferrulate as well as (5,6-isopropylidene)ascorbyl 2-benzoate.
The present invention therefore also relates to the novel compounds of the formulae Ia-c
where R1 to R3 are each, independently of one another,
Precisely these compounds are also preferably employed in compositions according to the invention.
Particularly preferred compounds here are those of the formula Ib or Ic in which R1 is a C6-28-alkylcarboxylic acid radical or C6-28-alkenylcarboxylic acid radical, preferably a radical of a natural fatty acid or fatty acid mixture.
For the purposes of the invention, L-ascorbyl 6-O-(4-hydroxy-3,5-dimethoxy)benzoate, L-ascorbyl 6-O-(3,4-dihydroxy)benzoate, L-ascorbyl 6-O-(4-hydroxy)benzoate, L-ascorbyl 6-O-(4-methoxy)benzoate, L-ascorbyl 6-O-(3-hydroxy)benzoate, L-ascorbyl 6-O-(3-methoxy)benzoate, L-ascorbyl 6-O-(2,5-dihydroxy)benzoate, L-ascorbyl 6-O-(4-hydroxy-3-methoxy)benzoate, L-ascorbyl 3-O-gallate, L-ascorbyl 2-O-gallate, L-ascorbyl 6-O-gallate 3-O-palmitate and L-ascorbyl 3-O-gallate 6-O-palmitate have proven particularly suitable.
The compositions according to the invention are usually either compositions which can be applied topically, for example cosmetic or dermatological formulations, or medicaments or foods or food supplements. The compositions comprise a cosmetically or dermatologically or pharmaceutically or food-suitable carrier and, depending on the desired property profile, optionally further suitable ingredients.
The compounds of the formula I are, in accordance with the invention, typically employed in amounts of from 0.01 to 20% by weight, preferably in amounts of from 0.1% by weight to 10% by weight and particularly preferably in amounts of from 1 to 8% by weight. The person skilled in the art is presented with absolutely no difficulties in selecting the amounts appropriately depending on the intended action of the composition.
Preference is therefore also given to compositions comprising at least one compound of the formula I which is characterised in that at least two adjacent radicals of the radicals R5 to R8 are hydroxyl or methoxy groups.
Particularly preferred compositions comprise at least one compound of the formula I which is characterised in that at least three adjacent radicals of the radicals R5 to R8 are hydroxyl or methoxy groups.
In order that the compounds of the formula I are able to develop their positive action particularly well on topical application, it may be preferred to allow the compounds of the formula I to penetrate into deeper skin layers. Several possibilities are available for this purpose. Firstly, the compounds of the formula I can have an adequate lipophilicity in order to be able to penetrate through the outer skin layer into epidermal layers. As a further possibility, corresponding transport agents, for example liposomes, which enable transport of the compounds of the formula I through the outer skin layers may also be provided in the composition. Finally, systemic transport of the compounds of the formula I is also conceivable. The composition is then designed, for example, in such a way that it is suitable for oral administration.
In general, the substances of the formula I act as free-radical scavengers. Free radicals of this type are not generated only by sunlight, but instead are formed under various conditions. Examples are anoxia, which blocks the flow of electrons upstream of the cytochrome oxidases and causes the formation of superoxide free-radical anions; inflammation associated, inter alia, with the formation of superoxide anions by the membrane NADPH oxidase of the leucocytes, but also associated with the formation (through disproportionation in the presence of iron(II) ions) of the hydroxyl free radicals and other reactive species which are normally involved in the phenomenon of phagocytosis; and lipid autoxidation, which is generally initiated by a hydroxyl free radical and produces lipidic alkoxy free radicals and hydroperoxides.
It is assumed that the preferred compounds of the formula I also act as enzyme inhibitors. They are thought to inhibit tyrosinase, histidine decarboxylase, protein kinases, elastase, aldose reductase and hyaluronidase, and therefore enable the intactness of the basic substance of vascular sheaths to be maintained. Furthermore, they are thought to inhibit catechol O-methyl transferase non-specifically, causing the amount of available catecholamines and thus the vascular strength to be increased. Furthermore, they are thought to inhibit AMP phosphodiesterase, giving the substances potential for inhibiting thrombocyte aggregation.
Owing to their properties, the compositions according to the invention are, in general, suitable for immune protection and for the protection of DNA and RNA. In particular, the compositions are suitable for the protection of DNA and RNA against oxidative attack, against free radicals and against damage due to radiation, in particular UV radiation. A further advantage of the compositions according to the invention is cell protection, in particular protection of Langerhans cells against damage due to the above-mentioned influences.
The compositions and compounds according to the invention are furthermore suitable for the prophylaxis and/or treatment of ischaemic reperfusion damage after organ transplants or heart attacks.
Owing to their antioxidative action, the compounds can be employed as active ingredient for stabilising formulations against oxidative degradation.
In addition, the compounds according to the invention are suitable as chelating agents for polyvalent metal ions, in particular the ions Ca2+, Cu2+, Fe2+ and Fe3+.
All these uses and the use of the compounds of the formula I for the preparation of compositions which can be employed correspondingly are expressly also a subject-matter of the present invention.
In particular, preferred compositions according to the invention are also suitable for the treatment of skin diseases associated with a defect in keratinisation which affects differentiation and cell proliferation, in particular for the treatment of acne vulgaris, acne comedonica, polymorphic acne, acne rosaceae, nodular acne, acne conglobata, age-induced acne, acne which arises as a side effect, such as acne solaris, medicament-induced acne or acne professionalis, for the treatment of other defects in keratinisation, in particular ichthyosis, ichthyosiform states, Darier's disease, keratosis palmoplantaris, leucoplasia, leucoplasiform states, herpes of the skin and mucous membrane (buccal) (lichen), for the treatment of other skin diseases associated with a defect in keratinisation and which have an inflammatory and/or immunoallergic component and in particular all forms of psoriasis which affect the skin, mucous membranes and fingers and toenails, and psoriatic rheumatism and skin atopy, such as eczema or respiratory atopy, or hypertrophy of the gums, it furthermore being possible for the compounds to be used for some inflammation which is not associated with a defect in keratinisation, for the treatment of all benign or malignant excrescence of the dermis or epidermis, which may be of viral origin, such as verruca vulgaris, verruca plana, epidermodysplasia verruciformis, oral papillomatosis, papillomatosis florida, and excrescence which may be caused by UV radiation, in particular epithelioma baso-cellulare and epithelioma spinocellulare, for the treatment of other skin diseases, such as dermatitis bullosa and diseases affecting the collagen, for the treatment of certain eye diseases, in particular corneal diseases, for overcoming or combating light-induced skin ageing associated with ageing, for reducing pigmentation and keratosis actinica and for the treatment of all diseases associated with normal ageing or light-induced ageing, for the prevention or healing of wounds/scars of atropy of the epidermis and/or dermis caused by locally or systemically applied corticosteroids and all other types of skin atropy, for the prevention or treatment of defects in wound healing, for the prevention or elimination of stretch marks caused by pregnancy or for the promotion of wound healing, for combating defects in sebum production, such as hyperseborrhoea in acne or simple seborrhoea, for combating or preventing cancer-like states or pre-carcinogenic states, in particular promyelocytic leukaemia, for the treatment of inflammatory diseases, such as arthritis, for the treatment of all virus-induced diseases of the skin or other areas of the body, for the prevention or treatment of alopecia, for the treatment of skin diseases or diseases of other areas of the body with an immunological component, for the treatment of cardiovascular diseases, such as arteriosclerosis or hypertension, and of non-insulin-dependent diabetes, and for the treatment of skin problems caused by UV radiation.
The antioxidant action of the compounds of the formula I can be demonstrated, for example, by means of 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. 2,2-Diphenyl-1-picrylhydrazyl is a free radical which is stable in solution. The unpaired electron results in a strong absorption band at 515 nm, and the solution has a dark violet colour. In the presence of a free-radical scavenger, the electron is paired, the absorption disappears, and the decoloration proceeds stoichiometrically taking into account the electrons taken up. The absorbance is measured in a photometer, The anti-free-radical property of the substance to be tested is determined by measuring the concentration at which 50% of the 2,2-diphenyl-1-picrylhydrazyl employed has reacted with the free-radical scavenger. This concentration is expressed as EC50, a value which can be considered to be a property of the substance under the given measurement conditions. The substance investigated is compared with a standard (for example tocopherol). The EC50 value here is a measure of the capacity of the respective compound to scavenge free radicals. The lower the EC50 value, the higher the capacity to scavenge free radicals. For the purposes of this invention, the expression “a large or high capacity to scavenge free radicals” is used if the EC50 value is lower than that of tocopherol.
A further important aspect for the action of the antioxidants is the time in which this EC50 value is reached. This time, measured in minutes, gives the TEC50 value, which allows a conclusion to be drawn on the rate at which these antioxidants scavenge free radicals.
The anti-free-radical efficiency (AE) (described in C. Sanchez-Moreno, J. A. Larrauri and F. Saura-Calixto in J. Sci. Food Agric. 1998, 76(2), 270-276) is given by the above-mentioned quantities in accordance with the following relationship:
A low AE (×10−3) is in the range up to about 10, a moderate AE is in the range from 10 to 20 and a high AE has in accordance with the invention values above 20.
It may be particularly preferred in accordance with the invention to combine fast-acting antioxidants with those having a slow or time-delayed action. Typical weight ratios of the fast-acting antioxidants to time-delayed antioxidants are in the range from 10:1 to 1:10, preferably in the range from 10:1 to 1:1, and for skin-protecting compositions particularly preferably in the range from 5:1 to 2:1. In other compositions which are likewise preferred in accordance with the invention, it may, however, be advantageous for the purposes of action optimisation for more time-delayed antioxidants than fast-acting antioxidants to be present. Typical compositions then exhibit weight ratios of the fast-acting antioxidants to time-delayed antioxidants in the range from 1:1 to 1:10, preferably in the range from 1:2 to 1:8.
The protective action against oxidative stress or against the effect of free radicals can thus be further improved if the compositions comprise one or more further antioxidants, the person skilled in the art being presented with absolutely no difficulties in selecting suitably fast-acting or time-delayed antioxidants.
In a preferred embodiment of the present invention, the composition is therefore a composition for the protection of body cells against oxidative stress, in particular for reducing skin ageing, characterised in that it preferably comprises one or more further antioxidants besides the one or more compounds of the formula I.
There are many proven substances known from the specialist literature which can be used as antioxidants, for example amino acids (for example glycine, histidine, tyrosine, tryptophan) and derivatives thereof, imidazoles (for example urocanic acid) and derivatives thereof, peptides, such as D,L-carnosine, D-carnosine, L-carnosine and derivatives thereof (for example anserine), carotinoids, carotenes (for example α-carotene, β-carotene, lycopene) and derivatives thereof, chlorogenic acid and derivatives thereof, lipoic acid and derivatives thereof (for example dihydrolipoic acid), aurothioglucose, propylthiouracil and other thiols (for example thioredoxin, glutathione, cysteine, cystine, cystamine and the glycosyl, N-acetyl, methyl, ethyl, propyl, amyl, butyl and lauryl, palmitoyl, oleyl, γ-linoleyl, cholesteryl and glyceryl esters thereof) and salts thereof, dilauryl thiodipropionate, distearyl thiodipropionate, thiodipropionic acid and derivatives thereof (esters, ethers, peptides, lipids, nucleotides, nucleosides and salts), and sulfoximine compounds (for example buthionine sulfoximines, homocysteine sulfoximine, buthionine sulfones, penta-, hexa- and heptathionine sulfoximine) in very low tolerated doses (for example pmol to pmol/kg), and also (metal) chelating agents (for example α-hydroxy fatty acids, palmitic acid, phytic acid, lactoferrin), α-hydroxy acids (for example citric acid, lactic acid, malic acid), humic acid, bile acid, bile extracts, bilirubin, biliverdin, EDTA, EGTA and derivatives thereof, unsaturated fatty acids and derivatives thereof, vitamin C and derivatives (for example ascorbyl palmitate, magnesium ascorbyl phosphate, ascorbyl acetate), tocopherols and derivatives (for example vitamin E acetate), vitamin A and derivatives (for example vitamin A palmitate), and coniferyl benzoate of benzoin resin, rutinic acid and derivatives thereof, α-glycosyl rutin, ferulic acid, furfurylideneglucitol, carnosine, butylhydroxytoluene, butylhydroxyanisole, nordihydroguaiaretic acid, trihydroxybutyrophenone, quercetin, uric acid and derivatives thereof, mannose and derivatives thereof, zinc and derivatives thereof (for example ZnO, ZnSO4), selenium and derivatives thereof (for example selenomethionine), stilbenes and derivatives thereof (for example stilbene oxide, trans-stilbene oxide).
Mixtures of antioxidants are likewise suitable for use in the cosmetic compositions according to the invention. Known and commercial mixtures are, for example, mixtures comprising, as active ingredients, lecithin, L-(+)-ascorbyl palmitate and citric acid (for example Oxynex® AP), natural tocopherols, L-(+)-ascorbyl palmitate, L-(+)-ascorbic acid and citric acid (for example Oxynex® K LIQUID), tocopherol extracts from natural sources, L-(+)-ascorbyl palmitate, L-(+)-ascorbic acid and citric acid (for example Oxynex® L LIQUID), DL-α-tocopherol, L-(+)-ascorbyl palmitate, citric acid and lecithin (for example Oxynex® LM) or butylhydroxytoluene (BHT), L-(+)-ascorbyl palmitate and citric acid (for example Oxynex® 2004). Antioxidants of this type are usually employed with compounds of the formula I in compositions of this type in ratios in the range from 1000:1 to 1:1000, preferably in amounts of from 100:1 to 1:100.
The compositions according to the invention may comprise vitamins as further ingredients. The cosmetic compositions according to the invention preferably comprise vitamins and vitamin derivatives selected from vitamin A, vitamin A propionate, vitamin A palmitate, vitamin A acetate, retinol, vitamin B, thiamine chloride hydrochloride (vitamin B1), riboflavin (vitamin B2), nicotinamide, vitamin C (ascorbic acid), vitamin D, ergocalciferol (vitamin D2), vitamin E, DL-α-tocopherol, tocopherol E acetate, tocopherol hydrogensuccinate, vitamin K1, esculin (vitamin P active ingredient), thiamine (vitamin B1), nicotinic acid (niacin), pyridoxine, pyridoxal, pyridoxamine (vitamin B6), pantothenic acid, biotin, folic acid and cobalamine (vitamin B12), particularly preferably vitamin A palmitate, vitamin C and derivatives thereof, DL-α-tocopherol, tocopherol E acetate, nicotinic acid, pantothenic acid and biotin. Vitamins are usually employed here with compounds of the formula I in ratios in the range from 1000:1 to 1:1000, preferably in amounts of from 100:1 to 1:100.
Of the phenols having an antioxidative action, the polyphenols, some of which are naturally occurring, are of particular interest for applications in the pharmaceutical, cosmetic or nutrition sector. For example, the flavonoids or bioflavonoids, which are principally known as plant dyes, frequently have an antioxidant potential. K. Lemanska, H. Szymusiak, B. Tyrakowska, R. Zielinski, I. M. C. M. Rietjens; Current Topics in Biophysics 2000, 24(2), 101-108, are concerned with effects of the substitution pattern of mono- and dihydroxyflavones. It is observed therein that dihydroxyflavones containing an OH group adjacent to the keto function or OH groups in the 3′,4′- or 6,7- or 7,8-position have antioxidative properties, while other mono- and dihydroxyflavones in some cases do not have antioxidative properties.
Quercetin (cyanidanol, cyanidenolon 1522, meletin, sophoretin, ericin, 3,3′,4′,5,7-pentahydroxyflavone) is frequently mentioned as a particularly effective antioxidant (for example C. A. Rice-Evans, N. J. Miller, G. Paganga, Trends in Plant Science 1997, 2(4), 152-159). K. Lemanska, H. Szymusiak, B. Tyrakowska, R. Zielinski, A. E. M. F. Soffers, I. M. C. M. Rietjens; Free Radical Biology & Medicine 2001, 31(7), 869-881, have investigated the pH dependence of the antioxidant action of hydroxyflavones. Quercetin exhibits the greatest activity amongst the structures investigated over the entire pH range.
Suitable antioxidants are furthermore compounds of the formula III
where R1 to R10 may be identical or different and are selected from
It has furthermore been found here that the combination of compounds according to the invention with vitamin E in compositions which have a high content of vitamin E, such as numerous natural oils, may be particularly advantageous since the compounds of the formula I according to the invention are able to suppress the pro-oxidative effect of the vitamin E.
Compositions which are particularly preferred in accordance with the invention also comprise pure UV filters in addition to the compounds of the formula I.
On use of the dibenzoylmethane derivatives which are particularly preferred as UV-A filters in combination with the compounds of the formula I, an additional advantage arises: the UV-sensitive dibenzoylmethane derivatives are additionally stabilised by the presence of the compounds of the formula I. The present invention therefore furthermore relates to the use of the compounds of the formula I for the stabilisation of dibenzoylmethane derivatives in compositions.
In principle, all UV filters are suitable for combination with the compounds of the formula I according to the invention. Particular preference is given to UV filters whose physiological acceptability has already been demonstrated. Both for UVA and UVB filters, there are many proven substances which are known from the specialist literature, for example
The compounds mentioned in the list should only be regarded as examples. It is of course also possible to use other UV filters.
These organic UV filters are generally incorporated into cosmetic formulations in an amount of from 0.5 to 10 percent by weight, preferably 1-8%.
Further suitable organic UV filters are, for example,
Further suitable UV filters are methoxyflavones corresponding to the earlier German patent application DE 10232595.2.
Organic UV filters are generally incorporated into cosmetic formulations in an amount of from 0.5 to 20 percent by weight, preferably 1-15%.
Conceivable inorganic UV filters are those from the group consisting of titanium dioxides, such as, for example, coated titanium dioxide (for example Eusolex® T-2000, Eusolex® T-AQUA), zinc oxides (for example Sachtotec®), iron oxides and also cerium oxides. These inorganic UV filters are generally incorporated into cosmetic compositions in an amount of from 0.5 to 20 percent by weight, preferably 2-10%.
Preferred compounds having UV-filtering properties are 3-(4′-methylbenzylidene)-dl-camphor, 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione, 4-isopropyldibenzoylmethane, 2-hydroxy-4-methoxybenzophenone, octyl methoxycinnamate, 3,3,5-trimethylcyclohexyl salicylate, 2-ethylhexyl 4-(dimethylamino)benzoate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate, 2-phenylbenzimidazole-5-sulfonic acid and the potassium, sodium and triethanolamine salts thereof.
The protective action against the damaging effects of UV radiation can be optimised by combining one or more compounds of the formula I with further UV filters.
Optimised compositions may comprise, for example, the combination of the organic UV filters 4′-methoxy-6-hydroxyflavone with 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione and 3-(4′-methylbenzylidene)-dl-camphor. This combination gives rise to broad-band protection, which can be supplemented by the addition of inorganic UV filters, such as titanium dioxide microparticles.
All the said UV filters can also be employed in encapsulated form. In particular, it is advantageous to employ organic UV filters in encapsulated form. In detail, the following advantages arise:
It is therefore preferred in accordance with the invention for one or more of the above-mentioned UV filters to be in encapsulated form. It is advantageous here for the capsules to be so small that they cannot be viewed with the naked eye. In order to achieve the above-mentioned effects, it is furthermore necessary for the capsules to be sufficiently stable and the encapsulated active ingredient (UV filter) only to be released to the environment to a small extent, or not at all.
Suitable capsules can have walls of inorganic or organic polymers. For example, U.S. Pat. No. 6,242,099 B1 describes the production of suitable capsules with walls of chitin, chitin derivatives or polyhydroxylated polyamines. Capsules which can particularly preferably be employed in accordance with the invention have walls which can be obtained by a sol-gel process, as described in the applications WO 00/09652, WO 00/72806 and WO 00/71084. Preference is again given here to capsules whose walls are built up from silica gel (silica; undefined silicon oxide hydroxide). The production of corresponding capsules is known to the person skilled in the art, for example from the cited patent applications, whose contents expressly also belong to the subject-matter of the present application.
The capsules in compositions according to the invention are preferably present in amounts which ensure that the encapsulated UV filters are present in the composition in the above-indicated amounts.
The compositions according to the invention may in addition comprise further conventional skin-protecting or skin-care active ingredients. These may in principle be any active ingredients known to the person skilled in the art.
These can be chromone derivatives. The term chromone derivatives is preferably taken to mean certain chromen-2-one derivatives which are suitable as active ingredients for the preventative treatment of human skin and human hair against ageing processes and harmful environmental influences. They simultaneously exhibit a low irritation potential for the skin, have a positive influence on water binding in the skin, maintain or increase the elasticity of the skin and thus promote skin smoothing. These compounds preferably conform to the formula IV
where
The proportion of one or more compounds selected from chromone derivatives in the composition according to the invention is preferably from 0.001 to 5% by weight, particularly preferably from 0.01 to 2% by weight, based on the composition as a whole.
It may furthermore be preferred for the composition according to the invention to comprise at least one repellent, where the repellent is preferably selected from N,N-diethyl-3-methylbenzamide, ethyl 3-(acetylbutylamino)propionate, dimethyl phthalate, butopyronoxyl, 2,3,4,5-bis(2-butylene)tetrahydro-2-furaldehyde, N,N-diethylcaprylamide, N,N-diethylbenzamide, o-chloro-N,N-diethylbenzamide, dimethyl carbate, di-n-propyl isocinchomeronate, 2-ethylhexane-1,3-diol, N-octylbicycloheptenedicarboximide, piperonyl butoxide, 1-(2-methylpropoxycarbonyl)-2-(hydroxyethyl)-piperidine or mixtures thereof, where it is particularly preferably selected from N,N-diethyl-3-methylbenzamide, ethyl 3-(acetylbutylamino)propionate, 1-(2-methylpropoxycarbonyl)-2-(hydroxyethyl)piperidine or mixtures thereof.
The compositions according to the invention which comprise repellents are preferably insect repellents. Insect repellents are available in the form of solutions, gels, sticks, rollers, pump sprays and aerosol sprays, with solutions and sprays forming the majority of the commercially available products. The basis for these two product forms are usually alcoholic or aqueous/alcoholic solutions with addition of fatting substances and slight perfuming.
Particularly preferred active ingredients are pyrimidinecarboxylic acids and/or aryl oximes.
Pyrimidinecarboxylic acids occur in halophilic microorganisms and play a role in osmoregulation of these organisms (E. A. Galinski et al., Eur. J. Biochem., 149 (1985) pages 135-139). Of the pyrimidinecarboxylic acids, particular mention should be made here of ectoin ((S)-1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) and hydroxyectoin ((S,S)-1,4,5,6-tetrahydro-5-hydroxy-2-methyl-4-pyrimidinecarboxylic acid) and derivatives thereof. These compounds stabilise enzymes and other biomolecules in aqueous solutions and organic solvents. Furthermore, they stabilise, in particular, enzymes against denaturing conditions, such as salts, extreme pH values, surfactants, urea, guanidinium chloride and other compounds.
Ectoin and ectoin derivatives, such as hydroxyectoin, can advantageously be used in medicaments. In particular, hydroxyectoin can be employed for the preparation of a medicament for the treatment of skin diseases. Other areas of application of hydroxyectoin and other ectoin derivatives are typically in areas in which, for example, trehalose is used as additive. Thus, ectoin derivatives, such as hydroxyectoin, can be used as protectant in dried yeast and bacteria cells. Pharmaceutical products, such as non-glycosylated, pharmaceutically active peptides and proteins, for example t-PA, can also be protected with ectoin or its derivatives.
Of the cosmetic applications, particular mention should be made of the use of ectoin and ectoin derivatives for the care of aged, dry or irritated skin. Thus, European patent application EP-A-0 671 161 describes, in particular, that ectoin and hydroxyectoin are employed in cosmetic compositions, such as powders, soaps, surfactant-containing cleansing products, lipsticks, rouge, make-ups, care creams and sunscreen preparations.
Preference is given here to the use of a pyrimidinecarboxylic acid of the following formula V
in which R1 is a radical H or C1-8-alkyl, R2 is a radical H or C1-4-alkyl, and R3, R4, R5 and R6 are each, independently of one another, a radical from the group consisting of H, OH, NH2 and C1-4-alkyl. Preference is given to the use of pyrimidinecarboxylic acids in which R2 is a methyl or ethyl group, and R1 or R5 and R6 are H. Particular preference is given to the use of the pyrimidinecarboxylic acids ectoin ((S)-1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) and hydroxyectoin ((S,S)-1,4,5,6-tetrahydro-5-hydroxy-2-methyl-4-pyrimidinecarboxylic acid). In this case, the compositions according to the invention preferably comprise pyrimidinecarboxylic acids of this type in amounts of up to 15% by weight. The pyrimidinecarboxylic acids are preferably employed here in ratios of from 100:1 to 1:100 with respect to the compounds of the formula I, with ratios in the range from 1:10 to 10:1 being particularly preferred.
Of the aryl oximes, preference is given to the use of 2-hydroxy-5-methyllaurophenone oxime, which is also known as HMLO, LPO or F5. Its suitability for use in cosmetic compositions is disclosed, for example, in DE-A-41 16 123. Compositions which comprise 2-hydroxy-5-methyllaurophenone oxime are accordingly suitable for the treatment of skin diseases which are accompanied by inflammation. It is known that compositions of this type can be used, for example, for the therapy of psoriasis, various forms of eczema, irritative and toxic dermatitis, UV dermatitis and further allergic and/or inflammatory diseases of the skin and integumentary appendages. Compositions according to the invention which, in addition to the compound of the formula I, additionally comprise an aryl oxime, preferably 2-hydroxy-5-methyllaurophenone oxime, exhibit surprising antiinflamematory suitability. The compositions here preferably comprise from 0.01 to 10% by weight of the aryl oxime, it being particularly preferred for the composition to comprise from 0.05 to 5% by weight of aryl oxime.
In a further, likewise preferred embodiment of the present invention, the composition according to the invention comprises at least one self-tanning agent.
Advantageous self-tanning agents which can be employed are, inter alia:
Mention should also be made of 5-hydroxy-1,4-naphthoquinone (juglone), which is extracted from the shells of fresh walnuts
Very particular preference is given to 1,3-dihydroxyacetone (DHA), a trifunctional sugar which occurs in the human body, and derivatives thereof.
The present invention furthermore relates to the use of a nanoparticulate UV protection agent according to the invention for the stabilisation of self-tanning agents, in particular dihydroxyacetone or dihydroxyacetone derivatives.
Furthermore, the compositions according to the invention may also comprise dyes and coloured pigments. The dyes and coloured pigments can be selected from the corresponding positive list in the German Cosmetics Regulation or the EU list of cosmetic colorants. In most cases, they are identical with the dyes approved for foods. Advantageous coloured pigments are, for example, titanium dioxide, mica, iron oxides (for example Fe2O3, Fe3O4, FeO(OH)) and/or tin oxide. Advantageous dyes are, for example, carmine, Berlin Blue, Chromium Oxide Green, Ultramarine Blue and/or Manganese Violet. It is particularly advantageous to select the dyes and/or coloured pigments from the following list. The Colour Index numbers (CINs) are taken from the Rowe Colour Index, 3rd Edition, Society of Dyers and Colourists, Bradford, England, 1971.
It may furthermore be favourable to select, as dye, one or more substances from the following group:
Also advantageous are oil-soluble natural dyes, such as, for example, paprika extract, β-carotene or cochineal.
Also advantageous for the purposes of the present invention are gel creams comprising pearlescent pigments. Particular preference is given to the types of pearlescent pigment listed below:
The basis for pearlescent pigments is formed by, for example, pulverulent pigments or castor oil dispersions of bismuth oxychloride and/or titanium dioxide as well as bismuth oxychloride and/or titanium dioxide on mica. The lustre pigment listed under CIN 77163, for example, is particularly advantageous.
Also advantageous are, for example, the following pearlescent pigment types based on mica/metal oxide:
Particular preference is given to, for example, the pearlescent pigments available from Merck under the trade names Timiron, Colorona or Dichrona.
The list of the said pearlescent pigments is of course not intended to be limiting. Pearlescent pigments which are advantageous for the purposes of the present invention can be obtained by numerous routes known per se. For example, other substrates apart from mica can also be coated with further metal oxides, such as, for example, silica and the like. For example, TiO2— and Fe2O3-coated SiO2 particles (“Ronasphere” grades), which are marketed by Merck and are particularly suitable for the optical reduction of fine wrinkles, are advantageous.
It may additionally be advantageous to completely omit a substrate such as mica. Particular preference is given to pearlescent pigments prepared using SiO2. Such pigments, which may additionally also have goniochromatic effects, are available, for example, from BASF under the trade name Sicopearl Fantastico.
It may also be advantageous to employ Engelhard/Mearl pigments based on calcium sodium borosilicate coated with titanium dioxide. These are available under the name Reflecks. Due to their particle size of 40-80 μm, they have a glitter effect in addition to the colour.
Also particularly advantageous are effect pigments available from Flora Tech under the trade name Metasomes Standard/Glitter in various colours (yellow, red, green and blue). The glitter particles here are in the form of mixtures with various auxiliaries and dyes (such as, for example, the dyes with the colour index (CI) numbers 19140, 77007, 77289 and 77491).
The dyes and pigments can be in individual form or in the form of a mixture and mutually coated with one another, with different colour effects generally being caused by different coating thicknesses. The total amount of dyes and colouring pigments is advantageously selected from the range from, for example, 0.1% by weight to 30% by weight, preferably from 0.5 to 15% by weight, in particular from 1.0 to 10% by weight, in each case based on the total weight of the compositions.
All compounds or components which can be used in the compositions are either known and commercially available or can be synthesised by known processes.
The one or more compounds of the formula I can be incorporated into cosmetic or dermatological compositions in the customary manner. Suitable compositions are those for external use, for example in the form of a cream, lotion or gel or as a solution which can be sprayed onto the skin. Suitable for internal use are administration forms such as capsules, coated tablets, powders, tablet solutions or solutions.
Examples which may be mentioned of application forms of the compositions according to the invention are: solutions, suspensions, emulsions, PIT emulsions, pastes, ointments, gels, creams, lotions, powders, soaps, surfactant-containing cleansing products, oils, aerosols and sprays Examples of other application forms are sticks, shampoos and shower products. Any desired customary carriers, auxiliaries and, if desired, further active ingredients may be added to the composition.
Preferred auxiliaries originate from the group consisting of preservatives, antioxidants, stabilisers, solubilisers, vitamins, colorants and odour improvers.
Ointments, pastes, creams and gels may comprise the customary carriers, for example animal and vegetable fats, waxes, paraffins, starch, tragacanth, cellulose derivatives, polyethylene glycols, silicones, bentonites, silica, talc and zinc oxide, or mixtures of these substances.
Powders and sprays may comprise the customary carriers, for example lactose, talc, silica, aluminium hydroxide, calcium silicate and polyamide powder, or mixtures of these substances. Sprays may additionally comprise the customary propellants, for example chlorofluorocarbons, propane/butane or dimethyl ether.
Solutions and emulsions may comprise the customary carriers, such as solvents, solubilisers and emulsifiers, for example water, ethanol, isopropanol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butyl glycol, oils, in particular cottonseed oil, peanut oil, wheatgerm oil, olive oil, castor oil and sesame oil, glycerol fatty acid esters, polyethylene glycols and fatty acid esters of sorbitan, or mixtures of these substances.
Suspensions may comprise the customary carriers, such as liquid diluents, for example water, ethanol or propylene glycol, suspending agents, for example ethoxylated isostearyl alcohols, polyoxyethylene sorbitol esters and polyoxyethylene sorbitan esters, microcrystalline cellulose, aluminium metahydroxide, bentonite, agar-agar and tragacanth, or mixtures of these substances.
Soaps may comprise the customary carriers, such as alkali metal salts of fatty acids, salts of fatty acid monoesters, fatty acid protein hydrolysates, isethionates, lanolin, fatty alcohol, vegetable oils, plant extracts, glycerol, sugars, or mixtures of these substances.
Surfactant-containing cleansing products may comprise the customary carriers, such as salts of fatty alcohol sulfates, fatty alcohol ether sulfates, sulfosuccinic acid monoesters, fatty acid protein hydrolysates, isethionates, imidazolinium derivatives, methyl taurates, sarcosinates, fatty acid amide ether sulfates, alkylamidobetaines, fatty alcohols, fatty acid glycerides, fatty acid diethanolamides, vegetable and synthetic oils, lanolin derivatives, ethoxylated glycerol fatty acid esters, or mixtures of these substances.
Face and body oils may comprise the customary carriers, such as synthetic oils, such as fatty acid esters, fatty alcohols, silicone oils, natural oils, such as vegetable oils and oily plant extracts, paraffin oils or lanolin oils, or mixtures of these substances.
Further typical cosmetic application forms are also lipsticks, lip-care sticks, mascara, eyeliner, eye-shadow, rouge, powder make-up, emulsion make-up and wax make-up, and sunscreen, pre-sun and after-sun preparations.
The preferred composition forms according to the invention include, in particular, emulsions.
Emulsions according to the invention are advantageous and comprise, for example, the said fats, oils, waxes and other fatty substances, as well as water and an emulsifier, as usually used for a composition of this type.
The lipid phase may advantageously be selected from the following group of substances:
For the purposes of the present invention, the oil phase of the emulsions, oleogels or hydrodispersions or lipodispersions is advantageously selected from the group consisting of esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 3 to 30 carbon atoms and saturated and/or unsaturated, branched and/or unbranched alcohols having a chain length of from 3 to 30 carbon atoms, or from the group consisting of esters of aromatic carboxylic acids and saturated and/or unsaturated, branched and/or unbranched alcohols having a chain length of from 3 to 30 carbon atoms. Ester oils of this type can then advantageously be selected from the group consisting of isopropyl myristate, isopropyl palmitate, isopropyl stearate, isopropyl oleate, n-butyl stearate, n-hexyl laurate, n-decyl oleate, isooctyl stearate, isononyl stearate, isononyl isononanoate, 2-ethylhexyl palmitate, 2-ethylhexyl laurate, 2-hexyldecyl stearate, 2-octyidodecyl palmitate, oleyl oleate, oleyl erucate, erucyl oleate, erucyl erucate and synthetic, semisynthetic and natural mixtures of esters of this type, for example jojoba oil.
The oil phase may furthermore advantageously be selected from the group consisting of branched and unbranched hydrocarbons and waxes, silicone oils, dialkyl ethers, or the group consisting of saturated and unsaturated, branched and unbranched alcohols, and fatty acid triglycerides, specifically the triglycerol esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms. The fatty acid triglycerides may advantageously be selected, for example, from the group consisting of synthetic, semi-synthetic and natural oils, for example olive oil, sunflower oil, soya oil, peanut oil, rapeseed oil, almond oil, palm oil, coconut oil, palm kernel oil and the like.
Any desired mixtures of oil and wax components of this type may also advantageously be employed for the purposes of the present invention. It may also be advantageous to employ waxes, for example cetyl palmitate, as the only lipid component of the oil phase.
The oil phase is advantageously selected from the group consisting of 2-ethylhexyl isostearate, octyldodecanol, isotridecyl isononanoate, isoeicosane, 2-ethylhexyl cocoate, C12-15-alkyl benzoate, caprylic/capric acid triglyceride and dicapryl ether.
Particularly advantageous are mixtures of C12-15-alkyl benzoate and 2-ethylhexyl isostearate, mixtures of C12-15-alkyl benzoate and isotridecyl isononanoate, as well as mixtures of C12-15-alkyl benzoate, 2-ethylhexyl isostearate and isotridecyl isononanoate.
Of the hydrocarbons, paraffin oil, squalane and squalene may advantageously be used for the purposes of the present invention.
Furthermore, the oil phase may also advantageously have a content of cyclic or linear silicone oils or consist entirely of oils of this type, although it is preferred to use an additional content of other oil-phase components in addition to the silicone oil or the silicone oils.
The silicone oil to be used in accordance with the invention is advantageously cyclomethicone (octamethylcyclotetrasiloxane). However, it is also advantageous for the purposes of the present invention to use other silicone oils, for example hexamethylcyclotrisiloxane, polydimethylsiloxane or poly(methylphenylsiloxane).
Also particularly advantageous are mixtures of cyclomethicone and isotridecyl isononanoate and of cyclomethicone and 2-ethylhexyl isostearate.
The aqueous phase of the compositions according to the invention optionally advantageously comprises alcohols, diols or polyols having a low carbon number, and ethers thereof, preferably ethanol, isopropanol, propylene glycol, glycerol, ethylene glycol, ethylene glycol monoethyl or monobutyl ether, propylene glycol monomethyl, monoethyl or monobutyl ether, diethylene glycol monomethyl or monoethyl ether and analogous products, furthermore alcohols having a low carbon number, for example ethanol, isopropanol, 1,2-propanediol or glycerol, and, in particular, one or more thickeners, which may advantageously be selected from the group consisting of silicon dioxide, aluminium silicates, polysaccharides and derivatives thereof, for example hyaluronic acid, xanthan gum, hydroxypropylmethylcellulose, particularly advantageously from the group consisting of the polyacrylates, preferably a polyacrylate from the group consisting of the so-called Carbopols, for example Carbopol grades 980, 981, 1382, 2984 or 5984, in each case individually or in combination.
In particular, mixtures of the above-mentioned solvents are used. In the case of alcoholic solvents, water may be a further constituent.
Emulsions according to the invention are advantageous and comprise, for example, the said fats, oils, waxes and other fatty substances, as well as water and an emulsifier, as usually used for a formulation of this type.
In a preferred embodiment, the compositions according to the invention comprise hydrophilic surfactants.
The hydrophilic surfactants are preferably selected from the group consisting of the alkylglucosides, acyl lactylates, betaines and coconut amphoacetates.
The alkylglucosides are themselves advantageously selected from the group consisting of the alkylglucosides which are distinguished by the structural formula
where R is a branched or unbranched alkyl radical having from 4 to 24 carbon atoms, and where {overscore (DP)} denotes a mean degree of glucosylation of up to 2.
The value {overscore (DP)} represents the degree of glucosidation of the alkylglucosides used in accordance with the invention and is defined as
in which p1, p2, p3 . . . pi represent the proportion of mono-, di-, tri- . . . i-fold glucosylated products in percent by weight. Products having degrees of glucosylation of 1-2, particularly advantageously of from 1.1 to 1.5, very particularly advantageously of 1.2-1.4, in particular of 1.3, are advantageously selected here in accordance with the invention.
The value DP takes into account the fact that alkylglucosides are generally, as a consequence of their preparation, in the form of mixtures of mono- and oligoglucosides. A relatively high content of monoglucosides, typically in the order of 40-70% by weight, is advantageous in accordance with the invention.
Alkylglucosides which are particularly advantageously used for the purposes of the invention are selected from the group consisting of octyl glucopyranoside, nonyl glucopyranoside, decyl glucopyranoside, undecyl glucopyranoside, dodecyl glucopyranoside, tetradecyl glucopyranoside and hexadecyl glucopyranoside.
It is likewise advantageous to employ natural or synthetic raw materials and auxiliaries or mixtures which are distinguished by an effective content of the active ingredients used in accordance with the invention, for example Plantaren® 1200 (Henkel KGaA), Oramix® NS 10 (Seppic).
The acyllactylates are themselves advantageously selected from the group consisting of the substances which are distinguished by the structural formula
where R1 is a branched or unbranched alkyl radical having from 1 to 30 carbon atoms, and M+ is selected from the group consisting of the alkali metal ions and the group consisting of ammonium ions which are substituted by one or more alkyl and/or one or more hydroxyalkyl radicals, or corresponds to half an equivalent of an alkaline earth metal ion.
For example, sodium isostearyl lactylate, for example the product Pathionic® ISL from the American Ingredients Company, is advantageous.
The betaines are advantageously selected from the group consisting of the substances which are distinguished by the structural formula
where R2 is a branched or unbranched alkyl radical having from 1 to 30 carbon atoms.
R2 is particularly advantageously a branched or unbranched alkyl radical having from 6 to 12 carbon atoms.
For example, capramidopropylbetaine, for example the product Tego® Betain 810 from Th. Goldschmidt AG, is advantageous.
A coconut amphoacetate which is advantageous for the purposes of the invention is, for example, sodium coconut amphoacetate, as available under the name Miranol® Ultra C32 from Miranol Chemical Corp.
The compositions according to the invention are advantageously characterised in that the hydrophilic surfactant(s) is (are) present in concentrations of 0.01-20% by weight, preferably 0.05-10% by weight, particularly preferably 0.1-5% by weight, in each case based on the total weight of the composition.
For use, the cosmetic and dermatological compositions according to the invention are applied to the skin and/or the hair in an adequate amount in the usual manner for cosmetics.
Cosmetic and dermatological compositions according to the invention may exist in various forms. Thus, they may be, for example, a solution, a water-free composition, an emulsion or microemulsion of the water-in-oil (W/O) or oil-in-water (O/W) type, a multiple emulsion, for example of the water-in-oil-in-water (W/O/W) type, a gel, a solid stick, an ointment or an aerosol. It is also advantageous to administer ectoins in encapsulated form, for example in collagen matrices and other conventional encapsulation materials, for example as cellulose encapsulations, in gelatine, wax matrices or liposomally encapsulated. In particular, wax matrices, as described in DE-A 43 08 282, have proven favourable. Preference is given to emulsions. O/W emulsions are particularly preferred. Emulsions, W/O emulsions and O/W emulsions are obtainable in a conventional manner.
Emulsifiers that can be used are, for example, the known W/O and O/W emulsifiers. It is advantageous to use further conventional co-emulsifiers in the preferred O/W emulsions according to the invention.
Co-emulsifiers which are advantageous according to the invention are, for example, O/W emulsifiers, principally from the group consisting of the substances having HLB values of 11-16, very particularly advantageously having HLB values of 14.5-15.5, so long as the O/W emulsifiers have saturated radicals R and R′. If the O/W emulsifiers have unsaturated radicals R and/or R′ or in the case of isoalkyl derivatives, the preferred HLB value of such emulsifiers may also be lower or higher.
It is advantageous to select the fatty alcohol ethoxylates from the group consisting of ethoxylated stearyl alcohols, cetyl alcohols, cetylstearyl alcohols (cetearyl alcohols). Particular preference is given to the following: polyethylene glycol (13) stearyl ether (steareth-13), polyethylene glycol (14) stearyl ether (steareth-14), polyethylene glycol (15) stearyl ether (steareth-15), polyethylene glycol (16) stearyl ether (steareth-16), polyethylene glycol (17) stearyl ether (steareth-17), polyethylene glycol (18) stearyl ether (steareth-18), polyethylene glycol (19) stearyl ether (steareth-19), polyethylene glycol (20) stearyl ether (steareth-20), polyethylene glycol (12) isostearyl ether (isosteareth-12), polyethylene glycol (13) isostearyl ether (isosteareth-13), polyethylene glycol (14) isostearyl ether (isosteareth-14), polyethylene glycol (15) isostearyl ether (isosteareth-15), polyethylene glycol (16) isostearyl ether (isosteareth-16), polyethylene glycol (17) isostearyl ether (isosteareth-17), polyethylene glycol (18) isostearyl ether (isosteareth-18), polyethylene glycol (19) isostearyl ether (isosteareth-19), polyethylene glycol (20) isostearyl ether (isosteareth-20), polyethylene glycol (13) cetyl ether (ceteth-13), polyethylene glycol (14) cetyl ether (ceteth-14), polyethylene glycol (15) cetyl ether (ceteth-15), polyethylene glycol (16) cetyl ether (ceteth-16), polyethylene glycol (17) cetyl ether (ceteth-17), polyethylene glycol (18) cetyl ether (ceteth-18), polyethylene glycol (19) cetyl ether (ceteth-19), polyethylene glycol (20) cetyl ether (ceteth-20), polyethylene glycol (13) isocetyl ether (isoceteth-13), polyethylene glycol (14) isocetyl ether (isoceteth-14), polyethylene glycol (15) isocetyl ether (isoceteth-15), polyethylene glycol (16) isocetyl ether (isoceteth-16), polyethylene glycol (17) isocetyl ether (isoceteth-17), polyethylene glycol (18) isocetyl ether (isoceteth-18), polyethylene glycol (19) isocetyl ether (isoceteth-19), polyethylene glycol (20) isocetyl ether (isoceteth-20), polyethylene glycol (12) oleyl ether (oleth-12), polyethylene glycol (13) oleyl ether (oleth-13), polyethylene glycol (14), oleyl ether (oleth-14), polyethylene glycol (15) oleyl ether (oleth-15), polyethylene glycol (12) lauryl ether (laureth-12), polyethylene glycol (12) isolauryl ether (isolaureth-12), polyethylene glycol (13) cetylstearyl ether (ceteareth-13), polyethylene glycol (14) cetylstearyl ether (ceteareth-14), polyethylene glycol (15) cetylstearyl ether (ceteareth-15), polyethylene glycol (16) cetylstearyl ether (ceteareth-16), polyethylene glycol (17) cetylstearyl ether (ceteareth-17), polyethylene glycol (18) cetylstearyl ether (ceteareth-18), polyethylene glycol (19) cetylstearyl ether (ceteareth-19), polyethylene glycol (20) cetylstearyl ether (ceteareth-20).
It is furthermore advantageous to select the fatty acid ethoxylates from the following group:
polyethylene glycol (20) stearate, polyethylene glycol (21) stearate, polyethylene glycol (22) stearate, polyethylene glycol (23) stearate, polyethylene glycol (24) stearate, polyethylene glycol (25) stearate, polyethylene glycol (12) isostearate, polyethylene glycol (13) isostearate, polyethylene glycol (14) isostearate, polyethylene glycol (15) isostearate, polyethylene glycol (16) isostearate, polyethylene glycol (17) isostearate, polyethylene glycol (18) isostearate, polyethylene glycol (19) isostearate, polyethylene glycol (20) isostearate, polyethylene glycol (21) isostearate, polyethylene glycol (22) isostearate, polyethylene glycol (23) isostearate, polyethylene glycol (24) isostearate, polyethylene glycol (25) isostearate, polyethylene glycol (12) oleate, polyethylene glycol (13) oleate, polyethylene glycol (14) oleate, polyethylene glycol (15) oleate, polyethylene glycol (16) oleate, polyethylene glycol (17) oleate, polyethylene glycol (18) oleate, polyethylene glycol (19) oleate, polyethylene glycol (20) oleate.
An ethoxylated alkyl ether carboxylic acid or salt thereof which can advantageously be used is sodium laureth-11 carboxylate. An alkyl ether sulfate which can advantageously be used is sodium laureth-14 sulfate. An ethoxylated cholesterol derivative which can advantageously be used is polyethylene glycol (30) cholesteryl ether. Polyethylene glycol (25) soyasterol has also proven successful. Ethoxylated triglycerides which can advantageously be used are the polyethylene glycol (60) evening primrose glycerides.
It is furthermore advantageous to select the polyethylene glycol glycerol fatty acid esters from the group consisting of polyethylene glycol (20) glyceryl laurate, polyethylene glycol (21) glyceryl laurate, polyethylene glycol (22) glyceryl laurate, polyethylene glycol (23) glyceryl laurate, polyethylene glycol (6) glyceryl caprate/caprinate, polyethylene glycol (20) glyceryl oleate, polyethylene glycol (20) glyceryl isostearate, polyethylene glycol (18) glyceryl oleate/cocoate.
It is likewise favourable to select the sorbitan esters from the group consisting of polyethylene glycol (20) sorbitan monolaurate, polyethylene glycol (20) sorbitan monostearate, polyethylene glycol (20) sorbitan monoisostearate, polyethylene glycol (20) sorbitan monopalmitate, polyethylene glycol (20) sorbitan monooleate.
The following can be employed as optional W/O emulsifiers, but ones which may nevertheless be advantageous for the purposes of the invention:
fatty alcohols having from 8 to 30 carbon atoms, monoglycerol esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms, diglycerol esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms, monoglycerol ethers of saturated and/or unsaturated, branched and/or unbranched alcohols having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms, diglycerol ethers of saturated and/or unsaturated, branched and/or unbranched alcohols having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms, propylene glycol esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms, and sorbitan esters of saturated and/or unsaturated, branched and/or unbranched alkanecarboxylic acids having a chain length of from 8 to 24 carbon atoms, in particular 12-18 carbon atoms.
Particularly advantageous W/O emulsifiers are glyceryl monostearate, glyceryl monoisostearate, glyceryl monomyristate, glyceryl monooleate, diglyceryl monostearate, diglyceryl monoisostearate, propylene glycol mono-stearate, propylene glycol monoisostearate, propylene glycol monocaprylate, propylene glycol monolaurate, sorbitan monoisostearate, sorbitan monolaurate, sorbitan monocaprylate, sorbitan monoisooleate, sucrose distearate, cetyl alcohol, stearyl alcohol, arachidyl alcohol, behenyl alcohol, isobehenyl alcohol, selachyl alcohol, chimyl alcohol, polyethylene glycol (2) stearyl ether (steareth-2), glyceryl monolaurate, glyceryl monocaprinate and glyceryl monocaprylate.
The preferred compositions according to the invention are particularly suitable for protecting human skin against ageing processes and against oxidative stress, i.e. against damage caused by free radicals, as are produced, for example, by solar irradiation, heat or other influences. In this connection, they are in the various administration forms usually used for this application. For example, they may, in particular, be in the form of a lotion or emulsion, such as in the form of a cream or milk (O/W, W/O, O/W/O, W/O/W), in the form of oily-alcoholic, oily-aqueous or aqueous-alcoholic gels or solutions, in the form of solid sticks or may be formulated as an aerosol.
The composition may comprise cosmetic adjuvants which are usually used in this type of composition, such as, for example, thickeners, softeners, moisturisers, surface-active agents, emulsifiers, preservatives, antifoams, perfumes, waxes, lanolin, propellants, dyes and/or pigments Which colour the composition itself or the skin, and other ingredients usually used in cosmetics.
The dispersant or solubiliser used can be an oil, wax or other fatty substance, a lower monoalcohol or lower polyol or mixtures thereof. Particularly preferred monoalcohols or polyols include ethanol, isopropanol, propylene glycol, glycerol and sorbitol.
A preferred embodiment of the invention is an emulsion in the form of a protective cream or milk which, apart from the compound(s) of the formula I, comprises, for example, fatty alcohols, fatty acids, fatty acid esters, in particular triglycerides of fatty acids, lanolin, natural and synthetic oils or waxes and emulsifiers in the presence of water.
Further preferred embodiments are oily lotions based on natural or synthetic oils and waxes, lanolin, fatty acid esters, in particular triglycerides of fatty acids, or oily-alcoholic lotions based on a lower alcohol, such as ethanol, or a glycerol, such as propylene glycol, and/or a polyol, such as glycerol, and oils, waxes and fatty acid esters, such as triglycerides of fatty acids.
The composition according to the invention may also be in the form of an alcoholic gel which comprises one or more lower alcohols or polyols, such as ethanol, propylene glycol or glycerol, and a thickener, such as siliceous earth. The oily-alcoholic gels also comprise natural or synthetic oil or wax.
The solid sticks consist of natural or synthetic waxes and oils, fatty alcohols, fatty acids, fatty acid esters, lanolin and other fatty substances.
If a composition is formulated as an aerosol, the customary propellants, such as alkanes, fluoroalkanes and chlorofluoroalkanes, are generally used.
The cosmetic composition may also be used to protect the hair against photochemical damage in order to prevent colour changes, bleaching or damage of a mechanical nature. In this case, a suitable formulation is in the form of a rinse-out shampoo, lotion, gel or emulsion, the composition in question being applied before or after shampooing, before or after colouring or bleaching or before or after permanent waving. It is also possible to select a composition in the form of a lotion or gel for styling or treating the hair, in the form of a lotion or gel for brushing or blow-waving, in the form of a hair lacquer, permanent waving composition, colorant or bleach for the hair. Besides the compound(s) of the formula I, the composition having light-protection properties may comprise various adjuvants used in this type of composition, such as surface-active agents, thickeners, polymers, softeners, preservatives, foam stabilisers, electrolytes, organic solvents, silicone derivatives, oils, waxes, antigrease agents, dyes and/or pigments which colour the composition itself or the hair, or other ingredients usually used for hair care.
The present invention furthermore relates to a process for the preparation of a composition which is characterised in that at least one compound of the formula I having radicals as described above is mixed with a carrier which is suitable cosmetically or dermatologically or for foods, and to the use of a compound of the formula I for the preparation of a composition having antioxidant properties.
The compositions according to the invention can be prepared using techniques which are well known to the person skilled in the art.
The mixing can result in dissolution, emulsification or dispersion of the compound of the formula I in the carrier.
In a process which is preferred in accordance with the invention, the compound of the formula I is prepared by the esterification of ascorbic acid containing hydroxyl groups which are optionally protected in a suitable manner, using at least one hydroxybenzoic acid or an activated derivative thereof and optionally an alkyl- or alkenylcarboxylic acid or an activated derivative thereof.
Numerous methods for the esterification of ascorbic acid are known to the person skilled in the art from the literature. The compounds can be obtained, for example, by the reaction of gallic acid with ascorbic acid in concentrated sulfuric acid, analogously to the synthesis of 6-ascorbyl palmitate. Corresponding reactions are described, for example, in Gan, L., Seib, P. A. J. Carbohydrate Chemistry, 1998, 17 (3), 397-404.
Under the reaction conditions described therein, the formation of mixtures comprising L-ascorbyl 5-O-gallate and L-ascorbyl 6-O-gallate is observed. After an extended standing time, L-ascorbyl 5-O-gallate decreases in concentration. Conversion of the two compounds into one another is also observed in aqueous solution, with the equilibrium being pH-dependent, but L-ascorbyl 6-O-gallate is always the predominant form.
2- or 3-esterified ascorbic acid derivatives can be obtained if the more reactive hydroxyl groups in the 5-, 6- and, if present, 3-position are protected during the reaction. This can be achieved using conventional protecting groups, such as, for example, by etherification of isopropylidene radicals or benzyl radicals. Reactions of this type are discussed below by way of example for the preparation of L-ascorbyl 3-O-gallate, L-ascorbyl 2-O-gallate and L-ascorbyl 3-O-palmitate 6-O-gallate:
5,6-O-Isopropylidene-L-ascorbic acid is reacted with gallyl chloride in CH2Cl2 using pyridine as base to give 5,6-O-isopropylidene-L-ascorbyl 3-O-gallate. Acidic hydrolysis thereof gives L-ascorbyl 3-O-gallate.
5,6-O-Isopropylidene-L-ascorbic acid is reacted with benzyl bromide and NaH as base to give 5,6-O-isopropylidene-3-O-benzyl-L-ascorbic acid, which is in turn reacted with gallyl chloride in CH2Cl2 using pyridine as base to give 5,6-O-isopropylidene-3-O-benzyl-L-ascorbyl 2-O-gallate. Hydrogenation and subsequent acidic hydrolysis gives L-ascorbyl 2-O-gallate.
L-ascorbyl 6-O-gallate is reacted with palmityl chloride in a solvent mixture comprising dimethylformamide/dichloromethane using pyridine as base.
L-ascorbyl 6-O-palmitate is reacted with gallyl chloride in a solvent mixture comprising dimethylformamide/dichloromethane using pyridine as base.
It has also been noted that compounds of the formula I can have a stabilising effect on the composition. When used in corresponding products, the latter are thus also stable for longer and do not change their appearance. In particular, the effectiveness of the ingredients, for example vitamins, is retained even in the case of application over extended periods or extended storage. This is, inter alia, particularly advantageous in the case of compositions for protecting the skin against the effect of UV rays since these cosmetics are exposed to particularly high stresses by UV radiation.
The positive effects of compounds of the formula I give rise to their particular suitability for use in cosmetic or pharmaceutical compositions.
The properties of compounds of the formula I should likewise be regarded as positive for use in foods or as food supplements or as functional foods. The further explanations given for foods also apply correspondingly to food supplements and functional foods.
The foods which can be enriched with one or more compounds of the formula I in accordance with the present invention include all materials which are suitable for consumption by animals or consumption by humans, for example vitamins and provitamins thereof, fats, minerals or amino acids. (The foods may be solid, but also liquid, i.e. in the form of a beverage). The present invention accordingly furthermore relates to the use of a compound of the formula I as food additive for human or animal nutrition, and compositions which are foods or food supplements and comprise corresponding carriers.
Foods which can be enriched with one or more compounds of the formula I in accordance with the present invention are, for example, also foods which originate from a single natural source, such as, for example, sugar, unsweetened juice, squash or puree of a single plant species, such as, for example, unsweetened apple juice (for example also a mixture of different types of apple juice), grapefruit juice, orange juice, apple compote, apricot squash, tomato juice, tomato sauce, tomato puree, etc. Further examples of foods which can be enriched with one or more compounds of the formula I in accordance with the present invention are corn or cereals from a single plant species and materials produced from plant species of this type, such as, for example, cereal syrup, rye flour, wheat flour or oat bran. Mixtures of foods of this type are also suitable for being enriched with one or more compounds of the formula I in accordance with the present invention, for example multivitamin preparations, mineral mixtures or sweetened juice. As further examples of foods which can be enriched with one or more compounds of the formula I in accordance with the present invention, mention may be made of food preparations, for example prepared cereals, biscuits, mixed drinks, foods prepared especially for children, such as yoghurt, diet foods, low-calorie foods or animal feeds.
The foods which can be enriched with one or more compounds of the formula I in accordance with the present invention thus include all edible combinations of carbohydrates, lipids, proteins, inorganic elements, trace elements, vitamins, water or active metabolites of plants and animals.
The foods which can be enriched with one or more compounds of the formula I in accordance with the present invention are preferably administered orally, for example in the form of meals, pills, tablets, capsules, powders, syrup, solutions or suspensions.
The foods according to the invention enriched with one or more compounds of the formula I can be prepared using techniques which are well known to the person skilled in the art.
Due to their action as antioxidants or free-radical scavengers, compounds of the formula I are also suitable as medicament ingredients. Here, they support or replace natural mechanisms which scavenge free radicals in the body. The compounds of the formula I can in some cases be compared in terms of their action with free-radical scavengers such as vitamin C. Compounds of the formula I can be used, for example, for preventative treatment of inflammation and allergies of the skin and in certain cases for preventing certain types of cancer. Compounds of the formula I are particularly suitable for the preparation of a medicament for the treatment of inflammation, allergies and irritation, in particular of the skin. It is furthermore possible to prepare medicaments which act as a vein tonic, as an agent for increasing the strength of blood capillaries, as cuperose inhibitor, as chemical, physical or actinic erythema inhibitor, as agent for the treatment of sensitive skin, as decongestant, as desiccant, as slimming agent, as anti-wrinkle agent, as stimulator for the synthesis of components of the extracellular matrix, as strengthening agent for improving skin elasticity, and as anti-ageing agent. Furthermore, compounds of the formula I which are preferred in this connection exhibit antiallergic and antiinflammatory and antiirritative actions. They are therefore suitable for the preparation of medicaments for the treatment of inflammation or allergic reactions.
The invention is explained in greater detail below by means of examples. The invention can be carried out throughout the range claimed and is not restricted to the examples given here.
Concentrated sulfuric acid (40 ml) is initially introduced; then, firstly gallic acid (10 g, 58.1 mmol) and subsequently ascorbic acid (15 g, 85.2 mmol) are added at such a rate that the temperature does not rise above 30° C. The reaction mixture is stirred for 5 hours at 45° C. and for 20 hours at room temperature. The reaction mixture is subsequently added to ice (saturated with sodium chloride) and immediately extracted with ethyl acetate, stirred with activated carbon, filtered and evaporated virtually to dryness. The precipitated solid is filtered off with suction, giving 9.8 g (51% yield) of L-ascorbyl 6-gallate I and L-ascorbyl 5-gallate II (ratio: 8:2). After an extended standing time in solution, the concentration of L-ascorbyl 6-gallate I in the mixture increases. Evaporation of the filtrates gives 4 g of an oil of L-ascorbyl 6-gallate I (20% yield), which contains up to 5% of gallic acid as impurity.
1H NMR (DMSO-d6) d 7.00 (s, 1H), 6.92 (s, 1H), 4.75 (d, J=1.8 Hz, 1H), 4.28 (dd, J=11.0, 7.0 Hz, 1H), 4.19 (dd, J=11.0, 6.3 Hz, 1H), 4.08 (dd, J=6.3, 6.9 Hz, 1H).
13C NMR (DMSO-d6) d 39.5, 64.6, 65.6, 75.1, 108.6, 118.1, 119.1, 120.3, 137.9, 138.5, 145.3, 145.4, 152.2, 165.5, 167.4, 170.4.
EI MS (m/e) 267 (M+), 239, 211
H2SO4 (37 ml, 0.69 mol) is introduced into a 100 ml three-necked round-bottomed flask fitted with a mechanical stirrer and a thermometer. Vitamin C (15 g, 0.085 mol) and gallic acid (10 g, 0.058 mol) are added in portions with constant stirring at room temperature and under an argon atmosphere. The resultant suspension is warmed at 40° C. for 7 hours and then stirred overnight at room temperature. The reaction mixture is then poured into a mixture of crushed ice (100 g), NaCl (20 g) and methyl ethyl ketone (300 ml) and stirred vigorously; The aqueous phase is extracted with methyl ethyl ketone (2×150 ml), and the combined organic phases are washed with a saturated aqueous solution of NaCl (1×100 ml). Activated carbon is added to the organic phase, and the mixture is stirred for 20 minutes at room temperature. The activated carbon is subsequently removed by filtration, and the filtrate is dried over sodium sulfate and evaporated to dryness under reduced pressure. The residue is carefully recrystallised from methyl ethyl ketone, giving 15.35 g of ASG I (yield 80.3%, purity from 92 to 98%). Further crystallisation of this product from methyl ethyl ketone gives ASG I having a purity of 98%.
The same process is used for the synthesis of the substances L-ascorbyl 6-O-(4-hydroxy-3,5-dimethoxy)benzoate (2), L-ascorbyl 6-O-(3,4-dihydroxy)benzoate (3), L-ascorbyl 6-O-(4-hydroxy)benzoate (4), L-ascorbyl 6-O-(4-methoxy)benzoate (5), L-ascorbyl 6-O-(3-hydroxy)benzoate (6), L-ascorbyl 6-O-(3-methoxy)benzoate (7), L-ascorbyl 6-O-(2,5-dihydroxy)-benzoate (8) and L-ascorbyl 6-O-(4-hydroxy-3-methoxy)benzoate (9) using the corresponding aromatic acid components.
The antioxidant activity of the compounds according to the invention is determined compared with the activity of conventional antioxidants. The antioxidant activity here is taken to mean the ability to function as hydrogen or electron donor and thus to be able to scavenge free radicals.
DPPH Assay
A stock solution of 2,2-diphenyl-1-picrylhydrazyl (DPPH) in ethanol is prepared (0.025 g/l of DPPH free radicals). Aliquots of this solution are mixed with various concentrations of the compound to be tested. The absorbance is in each case measured at 515 nm, 25° C. and 1 cm.
As EC50, the value is determined at which 50% of the original DPPH free-radical concentration is still present. The lower this value, the higher the corresponding antioxidant activity.
The reaction time necessary to achieve this value is indicated in the value TEC50 (in minutes).
The anti-free-radical efficiency (AE) is obtained from this in accordance with the following relationship:
A higher AE value here indicates a higher activity against free radicals.
The following table shows the results of the DPPH assay:
The antioxidative action of substances 1 to 7 from Example 1 b against the DPPH free radical is summarised in the following table. (DPPH free-radical scavenging shows the amount of antioxidant (in mg) needed to inhibit 1 mmol of DPPH):
ASG I exhibits a significantly greater antioxidative action than vitamin C or derivatives thereof. Only 54 mg of ASG I are sufficient to eliminate 1 mmol of the DPPH free radical. Substance 3 likewise exhibits a great antioxidative action. Analogues 2, 4 and 5 exhibit virtually the same reducing action as vitamin C.
TEAC Assay
Reaction of ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] with potassium peroxodisulfate in aqueous solution gives a stable free-radical cation. This free-radical cation has absorption maxima at 645 nm, 734 nm and 815 nm. The addition of an antioxidant to the ABTS free-radical cation results in reduction to ABTS. The magnitude of this conversion depends on the activity and concentration of the antioxidant and on the duration of the reaction. The reduction is evident from the decrease in absorbance, and the percentage of reduced ABTS is determined as a function of concentration and time and calculated relative to the reactivity of trolox (TEAC). The TEAC value indicates the concentration of trolox which causes the same percentage of absorption inhibition of the free-radical cation at 734 nm as 1 mmol/l of the substance to be investigated. This method can be used for the determination of antioxidants which are soluble in water or organic solvents (according to: Re, R., Pellegrini, N., Proteggente, A., Pannala, A., Yang, M., & Rice, E. C. (1999) Antioxidant activity applying an improved ABTS radical cation decolorisation assay. Free Radical Biology and Medicine, 26, 1231-1237).
The absorbance values measured after six minutes are used. The percentage of reduced ABTS is plotted against the concentration of the active ingredient (ASG I from Example 1 or trolox), and the slope of the lines is determined. In order to determine the TEAC value of ASG I, the slope of the trolox lines is divided by the slope of the ASG I lines.
In the TEAC assay, ASG I (from Example 1) exhibits 365 times the activity of the trolox standard.
Lipid Assay
The free-radical initiator ABAP [2,2′-azobis(2-amidinopropane)] dihydrochloride ensures a constant rate of formation of peroxyl free radicals. ABAP, which is water-soluble per se, is dispersed in SDS micelles. Linoleic acid (cis,cis-9,12-octadecadienoic acid) is likewise dispersed in SDS micelles. The free radicals cause the oxidation of linoleic acid to the isomer having conjugated double bonds. The formation of the conjugated double bond can be determined through the increase in the absorbance at 236 nm. The ability of the antioxidant to inhibit the rate of formation is determined relative to the tocopherol standard (in accordance with: Pryor, W. A., Cornicelli, J. A., Devall, L. J., Tait, B., Trivedi, B. K. L. J., Witiak, D. T., & Wu, M. (1993) A rapid screening test to determine the antioxidant potencies of natural and synthetic antioxidants. J Org Chem, 58, 3521-3532).
The means of the absorbance changes/min are determined for the reference, active substance (ASG I from Example 1) and tocopherol, the percentage inhibition is calculated, and the value is standardised to tocopherol.
The value for the relative antioxidative efficiency (RAE) of ASG I is 0.69; i.e. 69% of the activity of tocopherol.
Superoxide Free-Radical Anion Scavenging Efficiency of ASG I (Hypoxanthine-Xanthine Oxidase Test)
Reaction of fresh xanthine oxidase with hypoxanthine in the presence of EDTA in aqueous solution gives superoxide free-radical anions.
The free-radical anions are determined spectrophotometrically via the reduction of nitroblue tetrazolium (NBT) to nitroblue diformazan. The reduction is evident from the decrease in the absorption band at 560 nm.
(A. J. Gomez, C. N. Lunardi, S. Gonzalez and A. C. Tedesco (2001) The antioxidant action of Polypodium leucotomos extract and kojic acid: reaction with reactive oxygen species, Braz. J. Med. Biol. Res. 34(11), 1487-1494)
The following table shows the results of the hypoxanthine-xanthine oxidase test. The IC50 is the value at which 50% of the original superoxide free-radical anion concentration is still present. The lower this value, the higher the corresponding antioxidant activity.
ASG I exhibits a significantly higher antioxidative activity in this test than vitamin C or trolox.
Rancimat Assay
The Rancimat method for determination of the oxidation stability of fats and oils is known from the literature (Läubli M. W., Bruttel P. A.: “Determination of the oxidation stability of fats and oils—comparison between the active oxygen method (AOCS Cd 12-57) and the Rancimat method”, Fat. Sci. Technol. 90; 56-58 (1988); or Metrohm “Application Bulletin” Metrohm, No. 232/1 d, “Determination of the antioxidant activity by the Rancimat method”; handbook: “Rancimat 679”, Metrohm, instrument for the determination of oxidation and thermal stability, use instructions 8.679.1001, Metrohm AG, CH-9100 Herisau (Switzerland)).
The table shows the respective protection factor exhibited by the substances mentioned at a concentration of 0.1% by weight in 4 g of soya oil at 120° and 15 l of air/h in the Rancimat test.
ASG I pre-dissolved in ethanol exhibits an excellent protection factor in this test. Pure ASG I only dissolves partially in the soya oil and therefore gives the lower protection factor.
Comparative Experiment for the Antioxidant Activity
The efficacy of ASG I is compared with that of its starting substances vitamin C and gallic acid. The table shows the antioxidative activity of ASG I measured by the respective test methods described above in comparison with vitamin C and gallic acid.
It is found that ASG I is far superior to the two isolated part-components or their physical mixture.
Time Dependence of the Antioxidative Activity
The investigation is carried out with a 1 mol % solution of ASG I in EtOH:H2O in the volume ratio 1:1 at 40° C.; a comparison is carried out with the reference substances vitamin C and 6-ascorbyl palmitate under the same conditions. The reducing action of each substance (DPPH test) as a function of time is investigated and expressed as the amount of substance in mg required to inhibit 1 mmol of the DPPH free radical (
The results of this investigation show that ASG I is not only an effective antioxidant, but also has a long-lasting and stable antioxidative action. After storage for 90 days at 40° C., the antioxidative action of ASG I is retained. Vitamin C and ascorbyl palmitate lose their antioxidative action over this period. In both substances, a considerable loss of activity is observed.
It is noteworthy here that although ASG I is stable as the pure substance, it does, however, undergo hydrolysis in aqueous solution. Under storage conditions (90 days at 40° C., 1 mol-percent solution in EtOH:H2O), only 50% of the initial concentration of ASG I is retained after 30 days. Nevertheless, the hydrolysis products of ASG I exhibit a constant antioxidative action, in contrast to the other vitamin C derivatives.
NO Pro-Oxidative Action
A disadvantage of some antioxidants is that they have pro-oxidative actions on other molecules, in particular in the presence of transition metals, such as iron and copper. A typical example of an antioxidant having a pro-oxidative action is vitamin C. In vitro, the combination of ascorbate, hydrogen peroxide and transition-metal ions forms a mixture with a high degree of pro-oxidative action and which forms hydroxyl free radicals, which are able to oxidise virtually any type of molecule.
It is therefore investigated whether ASG I has a pro-oxidative action caused by metal transitions. A simple UV spectrophotometric method (Graf, E.; Mahoney, J. R.; Byrant, R. G.; Eaton, J. W. J. Biol. Chem. 1984, 259, 3620) is used to determine the efficacy of ASG I as chelating agent for Fe3+ and Cu2+. The result is shown in graphic form in
The method used is based on the principle that the formation of hydroxyl free radicals catalysed by metal ions requires the availability of at least one iron coordination site which is either free or is occupied by a ligand which can easily be dissociated, such as water. This coordination with water can be completely replaced by stronger ligands, such as azide anion (N3—). ASG I—Fe3+ exhibits characteristic absorbances at 215 nm and 268 nm. No shift in the absorbance of the complex induced by N3− is evident, indicating strong complex-forming properties of ASG I. No iron coordination site is available in this complex. It is therefore possible to conclude that ASG I does not have a pro-oxidative action in vitro.
Tyrosinase is the key enzyme in the synthesis of melanin. Substances which inhibit tyrosinase activity are therefore suitable as skin-lightening active ingredients.
Test with Substrate L-Tyrosine
The action is also investigated with L-tyrosine as substrate and compared with that of reference substances. The substances and tyrosinase (10 units) are pre-incubated on ice for 10 minutes; tyrosine is then added (final concentration 4 mM), and the plates are incubated at 37° C. for 1 hour. The optical density at each test point is measured at 450 nm against the corresponding control without enzyme. The results of this investigation are shown in the following table.
It is found that ASG I has an inhibition action which is comparable with that of the kojic acid used as reference substance. The IC50 (concentration which reduces the tyrosinase activity by 50%) is 0.109 mM. ASG I is also clearly superior to vitamin C, which is a known tyrosinase inhibitor.
Formulations of cosmetic compositions which comprise compounds according to Examples 1-3 are indicated by way of example below. In addition, the INCI names of the commercially available compounds are indicated.
UV Pearl, OMC is the composition with the INCI name:
Water (for EU: Aqua), Ethylhexyl Methoxycinnamate, Silica, PVP, Chlorphenesin, BHT; this composition is commercially available under the name Eusolex®UV Pearl™OMC from Merck KGaA, Darmstadt.
The other UV Pearl products indicated in the tables each have an analogous composition with OMC replaced by the UV filters indicated.
) and after addition of NaN3 (----)
| Number | Date | Country | Kind |
|---|---|---|---|
| 10351342.6 | Oct 2003 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| 60574716 | May 2004 | US |
