Time-course effects of Vitex schiliebenii (Varbenaceae) solvent extracts on Anopheles gambiae giles s.s. larvae under simulated semi-field conditions

Abstract

Objectives: To determine the growth-disrupting effects of polar phyto-extracts of V. schilibenii on Anopheles gambiae larvae in a simulated semi-field condition and to undertake phytochemical screening of constituents present. Materials & Method: 3rd and early 4th instars of An. gambiae larvae were exposed to acetone and methanol extracts of stem bark and leaves of V. schiliebenii and their effects on larval, pupal and adult stages recorded. Phytochemical screening of the extracts was undertaken using standard methods. Results: The results revealed that Anopheles gambiae larvae were susceptible to V. schiliebeinii extracts with less than 20 % adult emergence at concentrations ≥ 25 ppm except for methanol extract of stem bark. About 11 % pupae emerged in V. schiliebenii acetone leaf extract (VSL 1) between day 6 and 10 but they did not transform into viable adults. Phytochemical screening revealed the presence of flavonoids, terpenoids, steroids, alkaloids, saponins and tannins in the extracts. Conclusion: Eco-friendly polar extracts of V. schiliebenii show potential for mosquito control in small breeding habitats, which may be a useful component in integrated control of malaria vectors. Characterization of the active constituents of the extracts of the plant is in progress.