Potential mode of action of a novel plumbagin as a mosquito repellent against the malarial vector Anopheles stephensi, (Culicidae: Diptera).

Plumbagin was isolated and characterized from the roots of Plumbago zeylanica using chromatography: TLC, Column chromatogram, HPLC, FTIR and 1H NMR. The isolated pure compounds were assayed for potency as inhibitors of: acetylcholine esterase (AchE), glutathione S-transferases (GST), superoxide dismutase (SOD), cytochrome P450 and α, ß-esterase, and for repellency with Anopheles stephensi at four different concentrations (25, 50, 75 and 100ppm). The enzyme assay against the pure compound reveals that the level of esterase and SOD was decreased significantly in contrast the level of GST and cytochrome P450 was increased significantly. Our results suggests that novel Plumbagin has significantly alters the level of enzyme comparable to the control. Evaluations resulted in Plumbagin producing maximum repellency scores against An. stephensi mosquitoes in dose dependent manner with highest repellence was observed in the 100ppm. Histological examination showed that the midgut, hindgut and muscles are the most affected tissues. These tissues affected with major changes including separation and collapse of epithelial layer and cellular vacuolization. The results support the utility of plant compound Plumbagin for vector control as an alternative to synthetic insecticides, however, more vigorous field trials are needed to determine viability under natural conditions.

Toxicity of aristolochic acids isolated from Aristolochia indica Linn (Aristolochiaceae) against the malarial vector Anopheles stephensi Liston (Diptera: Culicidae).

With the growth of resistance to overused insecticides, vector management has become highly problematic. Hence more concentration has been focused on botanicals. Therefore our present study was aimed to evaluate the toxicity of compounds, aristolochic acid I and aristolochic acid II from the methanol extract of Aristolochia indica L. (Aristolochiaceae) leaves on larvae of Anopheles stephensi L. (Diptera: Culicidae) employing World Health Organization standard larvicide testing procedures. The soxhlet extraction was carried out using polar solvent, methanol. The isolated toxic compounds were purified through RP-HPLC. The FTIR spectroscopic studies revealed different peak values with functional groups in the mixed compounds (AA-I and AA- II). These two aristolochic acids were further studied through (13)C and (1)HNMR analysis with confirmed by structures. Bioassay-guided fractionation through flash chromatography lead to the isolation of two larvicidal compounds namely aristolochic acid I and II. In these bioassays, the larvae were exposed to concentrations of 100, 250, 500,750 and 1000 ppm for each compound. Between the two, AA-I exerted no significant toxicity difference (P < 0.05) on mosquito larvae with LC50- 171.3, 209.8, 269.1, 502.3 ppm and LC90-751.6, 963.8, 972.7, 990.8 ppm compared to AA-II with LC50-134.8, 166.7, 240.4,543.2 ppm and LC90- 636.7, 792.5, 990.8, 986.2 ppm against first, second, third and fourth instars, respectively. Further, the isolated compounds were severely affecting the mosquito gut. From the results, A. indica toxic compounds could be considered as one of the influential applicant to bring about useful botanicals so as to prevent the resurrection of mosquito vectors.

Antimalarial efficacy of dynamic compound of plumbagin chemical constituent from Plumbago zeylanica Linn (Plumbaginaceae) against the malarial vector Anopheles stephensi Liston (Diptera: Culicidae).

In the present investigation, the effective root compound of plumbagin of Plumbago zeylanica (Plumbaginaceae) was evaluated for chemical constituent and antimalarial effect against the fourth instar larvae of Anopheles stephensi Liston (Diptera). In the chromatographic analyses of root compound with Rf value of 0.788 and NMR analyses also revealed that the effective compound contain naphthoquinone plumbagin were identified as the major chemical constituent. Larval mortality was observed after 3 h of exposure period. The plumbagin compound showed remarkable larvicidal activity against A. stephensi (LC50 32.65 and LC9072.27 ppm). Histopathological effects of compound was observed in the treated larvae. Based on the results, the plumbagin compound of P. zeylanica can be considered as a new source of natural larvicide for the control of malarial vector.

Effects of Bacillus subtilis metabolites on larval Aedes aegypti L.

The culture supernatant of a strain of Bacillus subtilis isolated from soil samples killed larvae of the mosquito Aedes aegypti. The metabolites produced by B. subtilis were characterized using high performance liquid chromatography (HPLC). Mortality rate was dose-dependent for all larval instars of A. aegypti. Log probit analysis (95% confidence level) revealed an LC50 of 1.73 and an LC90 3.71µg/ml. Molecular weights/masses of B. subtilis metabolites were confirmed using SDS-PAGE analysis. B. subtilis metabolites were confirmed using HPLC analysis. We demonstrate that secondary metabolites from B. subtilis have larvicidal activity against A. aegypti and may be suitable for the control of this and other mosquito vectors of human disease. The larvae to the metabolites, significant reduction in the activities of acetylcholinesterse, α-carboxylesterase, and acid phosphatases were recorded.

Larvicidal efficacy of Adhatoda vasica (L.) Nees against the bancroftian filariasis vector Culex quinquefasciatus Say and dengue vector Aedes aegypti L. in in vitro condition.

The larvicidal activities of methanolic fractions from Adhatoda vasica leaf extracts were investigated against the bancroftian filariasis vector Culex quinquefasciatus and dengue vector Aedes aegypti. The results indicated that the mortality rates was high at 100, 150, 200 and 250 ppm of methanol extract of fractions III with R (f) value 0.67 and methanol extract of fraction V with R (f) value 0.64 of A. vasica against all the larval instars of C. quinquefasciatus and A. aegypti. The result of log probit analysis (at 95% confidence level) revealed that lethal concentration, LC(50) and LC(90) values were 106.13 and 180.6 ppm for fraction III, 110.6 and 170 ppm for fraction V of C. quinquefasciatus. And, the LC(50) and LC(90) values were 157.5 and 215.5 ppm for fraction III of A. aegypti and 120 and 243.5 ppm for the fraction V of A. aegypti, respectively. All the tested fractions proved to have strong larvicidal activity (doses from 100 to 250 ppm) against C. quinquefasciatus and A. aegypti. In general, second instar was more susceptible than the later instar. The results achieved suggest that, in addition to their ethnopharmacology value, A. vasica may also serve as a natural larvicidal agent.