STUDIES OF INSECTICIDAL ACTIVITY IN EXTRACT FRACTIONS OF MELIA-VOLKENSII (GURKE)

Chromatographic fractions of a fruit extract of Melia volkensii (Gurke ), Meliacae, a tropical arid area plant containing potent insect growt h regulators, antifeedants and acute toxicity effects: A simple and se nsitive bioassay to detect biological activity during purification has been developed using 2nd instar Aedes aegypti larvae. At high doses, the extract has acute toxicity effects but at low doses it is growth i nhibiting, especially causing a disruption of the metamorphosis progra mme. Four TLC purified fractions have been obtained which have higher activity than azadirachtin. It is suggested that the modes of action o f two of the more lipophilic fractions is mainly neurotoxicity and tha t of the other two is mainly interference with the endocrine system es pecially in relation to moulting and tanning.