Etude théorique de la cyclocondensation [4+2] de N,N-diméthyl- N-(3-oxo-cyclohexe-1-enyl)-formamidine avec les 9H-carbazole 1,4-dione substitués et activés par le brome

Theoretical study of [4+2] cyclocondensation of N,N-dimethyl-N-(3-oxocyclohexe-1-enyl)-formamidine with substituted and bromo-activated 9Hcarbazole1,4-dioneA theoretical study of hetero-Diels-Alder reaction between N,N-diméthyl-N-(3-oxocyclohexe-1-enyl)-formamidine (aza-diene) and substituted 9H-carbazole-1,4-dione. This reaction is regioselective and is an effective method for synthesizing calothrixin B and its analogues. The rich-electron substituted dienophiles permit to acces to the major adducts. The theoretical results are consistent with experience

Novel synthesis of benzimidazole by Ring Contraction Rearrangement of benzodiazepine

Condensation of substituted aromatic ketones (acetophenone) and substituted aldehydes give unsaturated ketones 14 (chalcones) which react with o-phenylenediamine 7 to afford the corresponding benzodiazepines 15. Treatments of benzodiazepines under basic conditions give benzimidazole derivatives. Structures of all synthesized compounds have been characterized by their NMR and mass spectral data.Keywords: N’-Thioacylamidines, Chalcone, o-phenylenediamine, benzodiazepine, benzimidazole

Pollution of a Tropical Lagoon by the Determination of Organochlorine Coumpounds

The lagoon system of Ivory Coast with 1,200 km2 of area is one among the important in West Africa. In the context of national quality water assessment, study of chemicals has been carried out in the central basin and its surroundings. The samples taken in different stations have been extracted with hexane and purified on column of florisil deactivated at 5% at chemical treatment. The analysis by CPG/ECD has permitted to identify the organochlorine compound wastes such as the Lindan, Heptachlor, Dieldrin, Endrin, the metabolites of DDT (PP'DDD and PP'DDE) and PCBs. The PCA method showed the highest stations of contamination located to Abidjan, the main industrial and urban zones (PCB: 15-227 ng/g and DDT + DDD + DDE: 1.7-130 ng/g)

Dynamics of multiple insecticide resistance in the malaria vector Anopheles gambiae in a rice growing area in South-Western Burkina Faso

<p>Abstract</p> <p>Background</p> <p>Insecticide resistance of the main malaria vector, <it>Anopheles gambiae</it>, has been reported in south-western Burkina Faso, West Africa. Cross-resistance to DDT and pyrethroids was conferred by alterations at site of action in the sodium channel, the Leu-Phe <it>kdr </it>mutation; resistance to organophosphates and carbamates resulted from a single point mutation in the oxyanion hole of the acetylcholinesterase enzyme designed as <it>ace-1</it>^<it>R</it>.</p> <p>Methods</p> <p>An entomological survey was carried out during the rainy season of 2005 at Vallée du Kou, a rice growing area in south-western Burkina Faso. At the Vallée du Kou, both insecticide resistance mechanisms have been previously described in the M and S molecular forms of <it>An. gambiae</it>. This survey aimed i) to update the temporal dynamics and the circumsporozoite infection rate of the two molecular forms M and S of <it>An. gambiae </it>ii) to update the frequency of the Leu-Phe <it>kdr </it>mutation within these forms and finally iii) to investigate the occurrence of the <it>ace-1</it>^{<it>R </it>}mutation.</p> <p>Mosquitoes collected by indoor residual collection and by human landing catches were counted and morphologically identified. Species and molecular forms of <it>An. gambiae</it>, <it>ace-1</it>^{<it>R </it>}and Leu-Phe <it>kdr </it>mutations were determined using PCR techniques. The presence of the circumsporozoite protein of <it>Plasmodium falciparum </it>was determined using ELISA.</p> <p>Results</p> <p><it>Anopheles gambiae </it>populations were dominated by the M form. However the S form occurred in relative important proportion towards the end of the rainy season with a maximum peak in October at 51%. Sporozoite rates were similar in both forms. The frequency of the Leu-Phe <it>kdr </it>mutation in the S form reached a fixation level while it is still spreading in the M form. Furthermore, the <it>ace</it>-<it>1</it>^{<it>R </it>}mutation prevailed predominately in the S form and has just started spreading in the M form. The two mutations occurred concomitantly both in M and S populations.</p> <p>Conclusion</p> <p>These results showed that the Vallée du Kou, a rice growing area formerly occupied mainly by M susceptible populations, is progressively colonized by S resistant populations living in sympatry with the former. As a result, the distribution pattern of insecticide resistance mutations shows the occurrence of both resistance mechanisms concomitantly in the same populations. The impact of multiple resistance mechanisms in M and S populations of <it>An. gambiae </it>on vector control measures against malaria transmission, such as insecticide-treated nets (ITNs) and indoor residual spraying (IRS), in this area is discussed.</p

Insecticide resistance status in Anopheles gambiae in southern Benin

BACKGROUND: The emergence of pyrethroid resistance in Anopheles gambiae has become a serious concern to the future success of malaria control. In Benin, the National Malaria Control Programme has recently planned to scaling up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) for malaria prevention. It is, therefore, crucial to monitor the level and type of insecticide resistance in An. gambiae, particularly in southern Benin where reduced efficacy of insecticide-treated nets (ITNs) and IRS has previously been reported. METHODS: The protocol was based on mosquito collection during both dry and rainy seasons across forty districts selected in southern Benin. Bioassay were performed on adults collected from the field to assess the susceptibility of malaria vectors to insecticide-impregnated papers (permethrin 0.75%, delthamethrin 0.05%, DDT 4%, and bendiocarb 0.1%) following WHOPES guidelines. The species within An. gambiae complex, molecular form and presence of kdr and ace-1 mutations were determined by PCR. RESULTS: Strong resistance to permethrin and DDT was found in An. gambiae populations from southern Benin, except in Aglangandan where mosquitoes were fully susceptible (mortality 100%) to all insecticides tested. PCR showed the presence of two sub-species of An. gambiae, namely An. gambiae s.s, and Anopheles melas, with a predominance for An. gambiae s.s (98%). The molecular M form of An. gambiae was predominant in southern Benin (97%). The kdr mutation was detected in all districts at various frequency (1% to 95%) whereas the Ace-1 mutation was found at a very low frequency (<or= 5%). CONCLUSION: This study showed a widespread resistance to permethrin in An. gambiae populations from southern Benin, with a significant increase of kdr frequency compared to what was observed previously in Benin. The low frequency of Ace-1 recorded in all populations is encouraging for the use of bendiocarb as an alternative insecticide to pyrethroids for IRS in Benin

Arm-in-cage testing of natural human-derived mosquito repellents

BACKGROUND: Individual human subjects are differentially attractive to mosquitoes and other biting insects. Previous investigations have demonstrated that this can be attributed partly to enhanced production of natural repellent chemicals by those individuals that attract few mosquitoes in the laboratory. The most important compounds in this respect include three aldehydes, octanal, nonanal and decanal, and two ketones, 6-methyl-5-hepten-2-one and geranylacetone [(E)-6,10-dimethylundeca-5,9-dien-2-one]. In olfactometer trials, these compounds interfered with attraction of mosquitoes to a host and consequently show promise as novel mosquito repellents. METHODS: To test whether these chemicals could provide protection against mosquitoes, laboratory repellency trials were carried out to test the chemicals individually at different concentrations and in different mixtures and ratios with three major disease vectors: Anopheles gambiae, Culex quinquefasciatus and Aedes aegypti. RESULTS: Up to 100% repellency was achieved depending on the type of repellent compound tested, the concentration and the relative composition of the mixture. The greatest effect was observed by mixing together two compounds, 6-methyl-5-hepten-2-one and geranylacetone in a 1:1 ratio. This mixture exceeded the repellency of DEET when presented at low concentrations. The repellent effect of this mixture was maintained over several hours. Altering the ratio of these compounds significantly affected the behavioural response of the mosquitoes, providing evidence for the ability of mosquitoes to detect and respond to specific mixtures and ratios of natural repellent compounds that are associated with host location. CONCLUSION: The optimum mixture of 6-methyl-5-hepten-2-one and geranylacetone was a 1:1 ratio and this provided the most effective protection against all species of mosquito tested. With further improvements in formulation, selected blends of these compounds have the potential to be exploited and developed as human-derived novel repellents for personal protection

The effective population size of malaria mosquitoes: large impact of vector control.

Malaria vectors in sub-Saharan Africa have proven themselves very difficult adversaries in the global struggle against malaria. Decades of anti-vector interventions have yielded mixed results--with successful reductions in transmission in some areas and limited impacts in others. These varying successes can be ascribed to a lack of universally effective vector control tools, as well as the development of insecticide resistance in mosquito populations. Understanding the impact of vector control on mosquito populations is crucial for planning new interventions and evaluating existing ones. However, estimates of population size changes in response to control efforts are often inaccurate because of limitations and biases in collection methods. Attempts to evaluate the impact of vector control on mosquito effective population size (N(e)) have produced inconclusive results thus far. Therefore, we obtained data for 13-15 microsatellite markers for more than 1,500 mosquitoes representing multiple time points for seven populations of three important vector species--Anopheles gambiae, An. melas, and An. moucheti--in Equatorial Guinea. These populations were exposed to indoor residual spraying or long-lasting insecticidal nets in recent years. For comparison, we also analyzed data from two populations that have no history of organized vector control. We used Approximate Bayesian Computation to reconstruct their demographic history, allowing us to evaluate the impact of these interventions on the effective population size. In six of the seven study populations, vector control had a dramatic impact on the effective population size, reducing N(e) between 55%-87%, the exception being a single An. melas population. In contrast, the two negative control populations did not experience a reduction in effective population size. This study is the first to conclusively link anti-vector intervention programs in Africa to sharply reduced effective population sizes of malaria vectors