Screening of natural products for mosquito larvicidal activity against three major mosquito vectors Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi resulted in the identification of three potential plant extracts viz., Saraca indica/asoca, Nyctanthes arbor-tristis, and Clitoria ternatea for mosquito larval control. In the case of S. indica/asoca, the petroleum ether extract of the leaves and the chloroform extract of the bark were effective against the larvae of C. quinquefasciatus with respective LC(50) values 228.9 and 291.5 ppm. The LC(50) values of chloroform extract of N. arbor-tristis leaves were 303.2, 518.2, and 420.2 ppm against A. aegypti, A. stephensi, and C. quinquefasciatus, respectively. The methanol and chloroform extracts of flowers of N. arbor-tristis showed larvicidal activity against larvae of A. stephensi with the respective LC(50) values of 244.4 and 747.7 ppm. Among the methanol extracts of C. ternatea leaves, roots, flowers, and seeds, the seed extract was effective against the larvae of all the three species with LC(50) values 65.2, 154.5, and 54.4 ppm, respectively, for A. stephensi, A. aegypti, and C. quinquefasciatus. Among the three plant species studied for mosquito larvicidal activity, C. ternatea was showing the most promising mosquito larvicidal activity. The phytochemical analysis of the promising methanolic extract of the seed extract was positive for carbohydrates, saponins, terpenoids, tannins, and proteins. In conclusion, bioassay-guided fractionation of effective extracts may result in identification of a useful molecule for the control of mosquito vectors.

The problems of high cost and development of resistance in many vector mosquito species to several of the synthetic insecticides have revived interest in exploiting the pest control potential of plants ( Grainge & Ahamed 1988). In addition to application as general toxicants against mosquito immature, phytochemicals may also have potential uses as growth and reproduction inhibitors, repellents, and oviposition deterrents. Plants belonging to six families: Asteraceae, Cladophoraceae, Labiatae, Meliaceae, Oocystaceae, and Rutaceae appear to have potential for providing future mosquito control agents (Sukumar et al. 1991). Atlantia monophylla belonging to family Rutaceae has been earlier reported for insecticidal activity against pests of agricultural importance (Grainge & Ahamed 1988, Sukumar et al. 1991, but there has been no report on its activity against public health pests. The plant is available year round in Pondicherry, India. A study was therefore undertaken to test the extract of this plant for its efficacy against immature stages of selected mosquito species. stock solution was added to 249 ml of tap water in a 500 ml enamel bowl. MATERIALS AND METHODS Preparation of stock solution of plant extract -Effects on target species -Larvicidal and pupicidal activities of the methanolic extracts of A. monophylla were determined by following the standard procedure (WHO 1975). Twenty early fourth instar larvae and 20 pupae of three vector mosquito species, Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti (obtained from the cyclic colony that has been maintained for the past 24 years at the Centre) were transferred to 249 ml of tap water taken in 500 ml bowls. Five replicates were set up for each test concentration and the plant extract was tested at concentrations ranging from 0.001 to 5 mg/l with two replicates of control with addition of 1 ml of acetone alone to 249 ml of tap water. Bioassay was conducted at room temperature 27 ± 3 o C with 85% relative humidity. In the case of experiment for determining pupicidal activity, the mouth of each bowl containing pupae was covered with muslin cloth to prevent the escape of any emerged adult mosquitoes. Mortality in larvae/pupae was recorded 24 h posttreatment.Insect growth regulating (IGR) activity -Methanolic extract of A. monophylla was also tested for IGR activity against the three mosquito species. Twenty early third instar larvae of the three species were transferred into 500 ml enamel bowls containing 249 ml of tap water. The plant extract was tested at concentrations ranging from 0.001 to 2 mg/l. Each test concentration was replicated five times. Two replicates of control were also maintained. Mortality of the larvae and pupae was recorded at 24 h intervals. Observation was continued in treated and control bowls until the last immature pupated. The treated and untreated bowls containing pupae were kept separately in one-foot cages for adult emergence. Morphological abnormalities in pupae and adults and partially emerged adults were recorded as ...

Lymphatic filariasis is caused by infection with the parasitic filarial nematodes Wuchereria bancrofti, Brugia malayi and B. timori, transmitted by mosquitoes. The lack of an adulticidal drug poses a challenge to filariasis elimination, hence it is essential to develop an effective antifilarial drug which could either kill or permanently sterilize the adult worms. In the reported work the in vitro activity of a methanolic extract of fruits of Trachyspermum ammi (Apiaceae) against adult bovine filarial Setaria digitata worms has been investigated. A bioassay-guided fractionation was carried out by subjecting the crude extract to flash chromatography. HPLC analysis was done for the crude extract and active fraction. The crude extract and the active fraction showed significant activity against the adult S. digitata by both a worm motility and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] reduction assays. The isolated active principle was chemically characterized by IR, 1H-NMR and MS analysis and identified as a phenolic monoterpene. It was screened for in vivo antifilarial activity against the human filarial worm B. malayi in Mastomys coucha, showing macrofilaricidal activity and female worm sterility in vivo against B. malayi. The findings thus provide a new lead for development of a macrofilaricidal drug from natural products.

Methanolic extracts of 20 medicinal plants were screened at 1-10 mg/ml for in vitro macrofilaricidal activity by worm motility assay against adult Setaria digitata, the cattle filarial worm. Four plant extracts showed macrofilaricidal activity by worm motility at concentrations below 4 mg/ml and an incubation period of 100 min. Complete inhibition of worm motility and subsequent mortality was observed at 3, 2, 1 and 1 mg/ml, respectively, for Centratherum anthelminticum, Cedrus deodara, Sphaeranthus indicus and Ricinus communis. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) reduction assay was carried out at 1 mg ml(-1) and 4-h incubation period, and the results showed that C. deodara, R. communis, S. indicus and C. anthelminticum exhibited 86.56, 72.39, 61.20 and 43.15% inhibition respectively in formazan formation compared to the control.

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Aedes aegypti is the key vector of three important arboviral diseases -dengue, yellow fever and chikungunya. To identify volatile chemicals which could be used in odour based traps for Aedes mosquito surveillance, a few synthetic compounds and compound blends have been evaluated in an indigenously designed olfactometer. A total of 24 compounds and seven compound blends were screened against unfed adult female Ae. aegypti mosquitoes for attraction and compared with control group. The attractancy or repellency index of the test material to mosquitoes was calculated and rated them as class-1, class-2 and class-3 with rating values ranging 1-15, 16-33 and 34-100 respectively. Out of the 24 compounds tested, six were showing significant attractancy (P< 0.05) and among that 1-octene-3-ol showed maximum attractancy with a rating value of 57.81. Sixteen compounds showed significant repellency (P < 0.05) and among that with a rating value of 72.47, 1-hexene-3-ol showed strong repellent action against Ae. aegypti. All the seven blends showed significant mosquito attractancy (P < 0.05) and among that with a rating of 62.08 Myristic acid, Lactic acid and CO(2) blend exhibited first-rate mosquito attractancy.

Eleven amino-substituted 1,4-naphthoquinones were synthesized via the reaction of 1,4-naphthoquinone with different primary and secondary mono-and diamines in the presence of dichloromethane ethanol (1:2) solvent at room temperature. All compounds were purified by flash column chromatography, characterized by TLC, HPLC, 13 C-NMR, 1 H-NMR, and FT-IR spectral analysis and were evaluated in vitro for antifilarial activity using adult bovine filarial worm Setaria digitata by assessing worm motility and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction. Seven of the 11 compounds had macrofilaricidal activity with compounds 9 (2-[(1,3-dimethylbutyl) amino] naphthalene-1,4-dione) and 11 (2-(4-methylpiperazin-1-yl) naphthalene-1,4-dione) having maximum activity (ED 50 values of 0.91 and 1.2 mM, respectively, at 48 h). The effect of different substitutions on antifilarial activity is discussed. Drug Dev Res 71: 188-196, 2010.