Chemical composition and evaluation of mosquito larvicidal activity of Vitex payos extracts against Anopheles gambiae Giles S.S larvae
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Date
2013-08
Authors
Hassanali, Ahmed
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Publisher
ScopeMed
Abstract
AIM: The aim of this study was to evaluate the acetone and methanol root bark extracts of Vitex payos and different fractions thereof, following acetone extraction and column chromatographic separation, for their immediate toxicity and long term effects on Anopheles gambiae Giles sensu stricto larvae under simulated semi-field conditions.
METHODS: In the present study, acetone and methanol extracts and acetone chromatographic fractions were investigated against late
third/early fourth-instar larvae of laboratory reared A. gambiae. The tests were conducted according to the method of the World Health
Organization (WHO) on guidelines for laboratory and field testing of mosquito larvicides. In addition, chemical compositions of the extracts
were carried out using gas chromatography-mass spectrometry (GC-MS). The study was conducted in 2012.
RESULTS: Acetone chromatographic fractions showed significant larvicidal activity against A. gambiae larvae with LC50 values ranging
between 0.7 - 0.9 ppm. Dose-response relationships were established with the highest dose of 500 ppm causing over 85% mortality in all the
test extracts. Long-term (11-14 days) post-exposure observations at lower doses showed that the extracts achieved over 90% adult growth
inhibition with morphogenetic variations and behavioral changes. In acetone and methanol extracts, carbonyl compounds were determined as
the main constituents with percentage compositions of 34.26% and 23.53% respectively. The other class of compounds determined was the
phytoecdysteroids where gamma sitosterol (6.43%) was the major sterol in acetone extract while stigmasterol (2.83%) was major in
methanol extract.
CONCLUSION: Extracts and chromatographic fractions from V. payos possess larvicidal and/or insect growth regulatory (IGR) principles
which can be used in aquatic ecosystems by the local communities where most of the people cannot afford synthetic larvicides.
Description
10.5455
Keywords
Anopheles gambiae, Vitex payos,, larvicidal activity, phytoecdysteroids,, saponins,, growth inhibition.