Patent Application
20080269252
The present invention relates to the use of compounds derived from pyrimidinetrione of general formula (I) as defined below as acetylcholinesterase (AChE) inhibitors, to their use as insecticides and to the compositions comprising these derivatives.
Intensive control of insects is practiced in many parts of the world by large-scale treatment using insecticides, which has gradually resulted in the emergence of populations of insects resistant to the treatments.
The emergence of populations of insects resistant to the commonly used insecticides represents an important public health problem insofar as some insects are the vectors for the transmission of diseases to man, such as, for example, the mosquitoes which transmit malaria (Anopheles gambiae), yellow fever and dengue fever (Aedes aegypti) or viral encephalopathies (Culex tritaeniorhynchus and Culex pipiens).
Mention may be made, among the most widely used insecticides, of organophosphorus compounds and carbamates. The target of these two main families of insecticides is acetylcholinesterase (AChE), an essential enzyme which hydrolyzes acetylcholine in the cholinergic synapses. Inhibition of AChE prevents deactivation of the synaptic signal, thus resulting in a loss in control of cholinergic transmission.
Among the mechanisms of resistance, the selection of mutations which render AChE insensitive to organophosphorus and carbamate insecticides has been observed in numerous cases (Anazawa Y., Insect Biochem. Mol. Biol., 2003, 33(5), 509-514; Fallang A., Pest. Manag. Sci., 2004, 60(12), 1163-1170; Li F., Insect Biochem. Mol. Biol., 2004, 34(4), 397-405; Menozzi P., BMC Evol. Biol., 2004, 4(1), 4; Nabeshima T., Biochem. Biophys. Res. Commun., 2004, 313(3), 794-801; Vontas J G., Insect Mol. Biol. 2002, 11(4), 329-336; Walsh S B., Biochem. J., 2001, 359 (Pt I), 175-181).
The inventors have thus previously identified in the Culicidae (mosquitoes) the gene encoding AChE, the target of the organophosphorus compounds and carbamates. Furthermore, one and the same mutation (glycine to serine at position 119 according to the Torpedo AChE nomenclature) has been encountered in all the populations of several species of mosquitoes which exhibit a high level of resistance to organophosphorus compounds and to carbamates and in particular in Culex pipiens, Anopheles gambiae and Anopheles albimanus, namely the main vectors of yellow fever, malaria and viral encephalopathies (Weill et al., Insect Molecular Biology, 2004, 13(1), 1-7; Weill et al., Nature, 2003, 423, 136-137).
In view of the above, it is thus apparent that the development of novel strategies for combating insects represents a crucial health and economic challenge.
Many researchers have attempted to diversify the biological target in order to circumvent these established resistances. However, while such a diversification is desirable in the long term, it will not prevent the appearance of resistant populations and will require a major effort in order to achieve the level of knowledge already acquired with regard to the targets currently targeted.
Another possibility consists in looking for molecules which are effective with regard to the resistant forms of the targets already authenticated. The major advantage of this approach is the lower probability of the targets accepting an additional mutation without resulting in a deleterious effect due to a reduction in their activity.
The inventors have chosen this second approach and have set themselves the aim of finding novel insecticides capable of killing the populations of insects which have developed resistance to conventional insecticides.
Thus, the inventors have identified a family of compounds capable of inhibiting AChE and preferably of acting on AChE insensitive to organophosphorus compounds and to carbamates. Such compounds thus have insecticidal properties and are capable of acting in particular preferably on populations of insects which have developed resistance to conventional insecticides.
Thus, the compounds according to the present invention can advantageously be used to control the growth of populations resistant to organosphosphorus compounds and to carbamates. Furthermore, in view of the reduction of 40% in the specific activity occasioned by the first mutation, the probability of AChE retaining a sufficient activity following an additional mutation is not very great. The use of the insecticidal compounds of this type would thus make it possible to prevent the spreading of the species currently resistant while minimizing the risks of appearance of fresh resistance to these novel compounds.
Furthermore, the structure of these compounds makes it possible, for example by combinatorial chemistry, to obtain a large number of alternative forms of these compounds, which should make it possible to rapidly adapt them to the emergence of possible subsequent resistances. These molecules are also relatively unstable in an aqueous medium, which is an advantage in the protection of the environment (low persistence).
According to a first aspect, a subject matter of the invention is the use of at least one compound derived from pyrimidinetrione as AChE inhibitor, said compound corresponding to the following general formula (I):
in which: represents a bond which can be a single bond or a double bond;
R1 represents a group chosen from a hydrogen atom and a saturated or unsaturated, linear, branched or cyclic, C1-C6 alkyl group optionally substituted by a hydroxyl group or a halogen atom;
R2 represents a group chosen from an optionally substituted aryl group and a saturated or unsaturated, linear, branched or cyclic, C1-C4 alkyl group optionally substituted by one or more groups chosen from halogen atoms, hydroxyl groups, heterocycles comprising 1 to 5 carbon atoms and 1 to 5 heteroatoms, such as oxygen, sulfur and nitrogen;
R3 can be in a 3, 4 or 5 position of the ring and represents a group chosen from a hydrogen atom and a saturated or unsaturated, linear, branched or cyclic, C1-C4 alkyl group optionally substituted by a hydroxyl group or a halogen atom;
X1 represents an atom chosen from sulfur, nitrogen and oxygen;
X3, X4 and X5, which are identical or different, are chosen from a carbon atom and a nitrogen atom, at most two atoms from X3, X4 and X5 being nitrogen atoms; and
Y represents an atom chosen from oxygen and sulfur.
When R2 is a substituted aryl group, it is substituted by a C1-C4 alkyl or alkoxy group, such as, for example, a methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl or isobutyl group or a methoxy, ethoxy, isopropoxy or butoxy group. It can also be substituted by a hydroxyl group or a halogen atom chosen from chlorine, bromine, iodine and fluorine, in particular chlorine. Furthermore, the substitution of the aryl group can take place in the ortho, meta or para position and preferably in the meta or para position.
Mention may in particular be made, among the
rings which can be used in the above formula (I), of:
X1 having the same definition as above.
Patent application DE 3903404 discloses pyrimidinetrione derivatives used as insecticides and anthelmintics in particular.
European patent EP 0 455 300 discloses barbituric acid derivatives and their use as insecticides; the targets targeted being other than mosquitoes.
However, the compounds described in these two documents are different from those corresponding to the general formula (I) as defined above. In addition, none of the documents of the prior art suggests or mentions an inhibitory activity for AChE, in particular an inhibitory activity for an AChE form resistant to organophosphorus and carbamate insecticides.
According to a preferred form of the invention, when R1, represents a C1-C6 alkyl group, the latter is preferably a C1-C4 alkyl group and more preferably a methyl group. Thus, mention may in particular be made, among the preferred compounds according to the invention, of the compounds in which R1 is chosen from a hydrogen atom and a methyl group.
According to another preferred form of the invention, R2 represents an aryl group optionally substituted by a group chosen from a C1-C4 alkyl and a halogen atom and advantageously a phenyl optionally substituted by a group chosen from a C1-C4 alkyl and a halogen atom.
Mention may in particular be made, among the preferred compounds according to the invention, of the compounds in which R2 is chosen from a methyl, an allyl, a furyl group optionally substituted by a methyl, a butyl, an unsubstituted phenyl, a phenyl substituted by a methyl group in the meta position, a phenyl substituted by a methyl group in the para position, a phenyl disubstituted in the meta and para position by a methyl, a phenyl substituted by an ethyl in the para position, a phenyl substituted by a methoxy group in the meta position, a phenyl substituted by a methoxy group in the para position, a phenyl substituted by an ethoxy in the para position, a phenyl substituted by an isopropyl in the para position, a phenyl substituted by a chlorine atom in the para position, a phenyl substituted by a bromine atom in the para position, a phenyl substituted by a fluorine atom in the para position. In the preferred compounds according to the invention, Y advantageously represents an oxygen atom.
According to a preferred form of the invention, X1 is chosen from oxygen and sulfur.
Advantageously, the compounds according to the invention are compounds in which X3, X4 and X5 are identical and all represent a carbon atom.
Mention may in particular be made, among the preferred compounds according to the invention, of the compounds in which R3 is chosen from a hydrogen atom and a methyl group. Furthermore, R3 is advantageously in the 5 position of the furan, thiophene or pyrrole ring.
Mention may in particular be made, among the compounds of formula (I) above, of the following preferred compounds listed in table I:
The preferred compounds which are cited in the above table are known as such and are described in particular in the following publications: Vvedenskii, V M., Khimiya Geterotsiklicheskikh Soedinenii, 1969, 6, 1092-1095; El-Badawi, M., Journal of Science, 1990, 14(2), 581-600. However, their insecticidal activity has never been demonstrated in the prior art.
Due to the inhibitory activity for AChE exhibited by the compounds derived from pyrimidinetrione of general formula (I) according to the present invention, these compounds can also be used in the preparation of a medicament intended to treat disorders associated with dysfunctioning of AChE and in particular neurodegenerative diseases, such as Alzheimer's disease. Specifically, the compounds of the invention have shown an inhibitory activity with regard to recombinant human AChE.
According to a second aspect, the subject matter of the invention is the use of at least one compound of general formula (I) as insecticide.
All the preferred compounds of general formula (I) as defined above can be used as insecticide.
The compounds of general formula (I) can be used to control the growth of populations of various types of insects, in particular of the genus Aedes, Culiseta, Ochlerotatus, Uranoteania, Anopheles or Culex, preferably of the genus Anopheles or Culex, in particular for the deinfestation of inhabitated regions or more generally of regions where a human activity is carried out, such as agricultural regions, for example.
Mention may in particular be made, among the insects of the genus Anopheles or Culex, of the species chosen from Culex deserticola, Culex hortensis, Culex pipiens pipiens, Culex pipiens, Culex pipiens quinquefasciatus, Culex pipiens molestus, Culex tigripes, Anopheles albimanus, Anopheles arabiensis, Anopheles gambiae, Anopheles hyrcanus, Anopheles subpicus and Anopheles sundaicus.
According to a preferred form of the invention, the compounds of general formula (I) are used on populations of insects which have developed resistance to organophosphorus insecticides or to carbamates. This is because the inventors have found, surprisingly, that, while the activity of these compounds with regard to populations of insects sensitive to carbamates and to organophosphorus compounds is comparable with or even inferior to that of these insecticides which have been known for a long time, these compounds are much more active with regard to the populations of insects resistant to these conventional insecticides.
According to another preferred form, the compounds of general formula (I) according to the present invention are used in combination with at least one other conventional insecticide, thus making it possible to treat regions in which populations of insects more or less sensitive or resistant to the various conventional insecticides coexist. The combination of at least one compound of general formula (I) and of at least one insecticide chosen from carbamates and organophosphorus compounds constitutes another subject matter of the invention.
Application can be carried out conventionally, for example by sprinkling, spraying, diffusion, painting, dry treatment, wet treatment, dipping, suspending or crusting.
Due to the insecticidal properties exhibited by the pyrimidinetrione derivatives of general formula (I) according to the present invention, these compounds can also be used as comparative product in carrying out evaluation tests on insecticidal properties.
For practical operating reasons, the compounds of general formula (I) according to the present invention can be provided in the form of compositions.
Thus it is that, according to a third aspect, a subject matter of the invention is an insecticidal composition comprising at least one compound of general formula (I) in combination with a carrier appropriate for the use of the composition as insecticide.
In the composition according to the present invention, the active compounds are mixed with a solid carrier or are dissolved or dispersed in a liquid carrier. The compounds can also be used in combination with additional substances, such as emulsifiers, wetting agents, dispersing agents and stabilizers.
The compounds derived from pyrimidinetrione of general formula (I) and the compositions comprising them according to the present invention can be incorporated in conventional formulations, such as solutions, emulsions, suspensions, powders, foams, pastes, granules, aerosols, and the like, said formulations being prepared by conventional techniques well known to a person skilled in the art.
According to a preferred form, the insecticidal composition of the invention additionally comprises at least one other compound possessing an insecticidal activity and in particular an insecticidal compound chosen from organophosphorus compounds and carbamates.
Furthermore, the insecticidal composition can additionally comprise one or more other active substances, such as, for example, acaricides, fungicides, bactericides, manures, fertilizers, and the like.
The compositions according to the invention are effective against populations of insects of normal sensitivity or which are resistant to organophosphorus compounds or to carbamates, as well as all the developmental stages of insects. This is because, the acetylcholinesterase activity being required for correct transmission of the nervous influx, the compounds of the invention are inhibitors of AChE (wild-type or G119S-mutated) and are thus active as soon as the activity of the enzyme is required (sensitive larvae die from the eclosion, thus at the L1 developmental stage).
The application forms as described above relating to the use of pyrimidinetrione derivatives of general formula (I) as insecticides (sprinkling, spraying, and the like) are also applicable to the compositions comprising them, whether or not the latter additionally comprise other active substances or auxiliaries.
Finally, according to a final aspect, a subject matter of the invention is an insecticidal kit comprising at least one composition as described above in combination with a diffusion means which makes possible the application of said composition over a district composed of one or more agricultural and/or residential and/or forestry and/or marshy and/or steppe and/or savannah regions.
The present invention will be better understood with the help of the remainder of the description which will follow, which refers to examples demonstrating the property inhibiting AChE of several compounds derived from pyrimidinetrione of general formula (I) according to the invention and demonstrating the insecticidal property of these compounds and to the preparation of a composition comprising these compounds.
The compounds derived from pyrimidinetrione of general formula (I) according to the invention which are combined in table II below were tested for their inhibitory activity on AChE. These compounds are all sold by Chembridge Corporation (San Diego, USA).
The inhibitory properties of the compounds of the preceding table I are tested with regard to the AChE activity by either using a normal or G119S-mutated recombinant AChE or using extracts of larvae of mosquitoes which are sensitive (carrying normal AChE) or resistant (carrying G119S-mutated AChE) to organophosphorus compounds and carbamates.
The AChE activity is measured using the method described by Bourguet et al., Pest Biochem. Physiol., 1996, 55, 122-128, and which refers to the spectroscopic method described by Ellman G. L. et al. (Biochem. Pharmacol., 1961, 7, 88-95) using acetylthiocholine as substrate.
The inhibitory properties of the compounds according to the invention with regard to the activity of a G119S-mutated or normal recombinant Culex pipiens AChE1 are tested according to protocol described by Weill et al., Nature, 2003, 423, 136-137.
Each compound according to the invention is tested at different concentrations on lysates of Drosophile S2 cells transfected with an empty expression vector or an expression vector expressing normal or mutated AChE1. After expression, the cells are centrifuged for 15 minutes at 14 000 rpm and are subsequently lysed in a 0.25 M phosphate buffer comprising 1% Triton X100.
100 μl of supernatant originating from the centrifuging of the cell lysates at 10 000 rpm for 3 minutes are incubated for 15 minutes with 10 μl of each compound according to the invention at various concentrations. The activity of known inhibitors of AChE, namely tacrine and propoxur (insecticide of the carbamate type), is also tested in parallel with regard to the AChE activity (tacrine and propoxur are available commercially from ICN Biomedical and Bayer AG respectively).
For each compound tested, the concentration resulting in 50% inhibition of the AChE activity is determined (IC50 in μM). The effectiveness of the various compounds with regard to the mutated AChE activity, relative to that of the normal AChE, is estimated by the sensitive/insensitive ratio.
The results obtained (IC50 in μM and sensitive/insensitive ratio) are summarized below in table III.
2) Inhibitory Property with Regard to Extracts or Mosquito Larvae
Larvae of Culex pipiens mosquitoes which are sensitive or resistant to propoxur are milled in 400 μl of 0.25M phosphate buffer comprising 1% Triton X100. The homogenates are centrifuged at 10 000 rpm for 3 minutes.
The inhibition of the AChE1 activity is measured on the supernatant according to the method described in section 1), namely that 100 μl of supernatant are incubated for 15 minutes with 10 μl of compounds according to the invention at various concentrations. The activity of the known inhibitors of AChE, namely tacrine and propoxur, is also tested in parallel. The effectiveness of the various compounds with regard to the resistant larvae, relative to the sensitive larvae, is estimated by the sensitive/resistant ratio.
The results obtained (IC50 in μM and sensitive/resistant ratio) are summarized below in table IV.
These combined results show that the compounds of formula (I) according to the invention are capable of effectively inhibiting the AChE activity and in particular the activity of a mutated AChE.
The insecticidal activity of the compounds according to the invention denoted in table IV below is tested on larvae of mosquitoes Culex pipiens sensitive or resistant to the action of propoxur.
The larvae resistant or sensitive to propoxur are incubated in 24-well plates, at the rate of 15 stage-4 larvae per well, in 1 ml of tap water comprising different concentrations of compounds ranging from 0.31 to 50 μg/ml.
Larval mortality is measured after incubating for 24 hours. For each compound, the dose resulting in 50% mortality (LD50 in μM) is estimated using the log-Probit program (Raymond, M. (1985). Présentation d'un programme Basic d'analyse log-probit pour micro-ordinateur [Presentation of a Basic program for log-Probit analysis for a micro computer). Cahiers ORSTOM, série Entomologie médicale et Parasitologie, 23(2), 117-121; Raymond, M., Prato, G. and Ratsira, D. (1993). PROBIT, CNRS-UMII, Licence L93019. Avenix, 34680 St. Georges d'Orques, France.), the homogeneity of the dose/response being tested. The effectiveness of the different compounds with regard to the resistant larvae, relative to the sensitive larvae, is estimated by the sensitive/resistant ratio.
The results obtained (LD50 in μM and sensitive/resistant ratio) are summarized below in the following table V.
These results clearly demonstrate that the compounds of formula (I) according to the invention are effective as insecticides and in particular with regard to populations of insects which are resistant to conventional insecticides of the propoxur type.
42 mg of the compound (I) are introduced into 100 ml of tap water and then the mixture is stirred.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0501328 | Feb 2005 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2006/000307 | 2/10/2006 | WO | 00 | 8/10/2007 |
