Partial characterization and insecticidal properties of Ricinus communis L foliage flavonoids.

Aqueous leaf extract of Ricinus communis L (Euphorbiaceae), a cultivated plant in tropical countries, showed excellent insecticidal activity against Callosobruchus chinensis L (Coleoptera: Bruchidae). We have isolated and tested flavonoids as insecticidal and antimicrobial agents. The isolated flavonoids showed potential insecticidal, ovicidal and oviposition deterrent activities against C chinensis L. However, antimicrobial activity against the common microbial infestants of stored pulses, of which C chinensis is a major pest, was found to be insignificant. Two bands having Rf 0.63 and 0.69 were seen on HPTLC plates using mobile phase benzene + ethyl acetate + methanol + formic acid (12 + 4.5 + 2 + 1.5 by volume) as eluant. The Rf values and scanning of the spectrum in the ultraviolet region, showed identity with the flavonoids quercetin and kaempferol. This was further confirmed using HPLC and IR and UV spectrometry. HPLC and HPTLC chromatograms also suggested quercetin to be the major flavonoid present in the hydrolyzed aqueous leaf extract of R communis.

Antimicrobial and pesticidal activity of partially purified flavonoids of Annona squamosa.

Foliar extracts of Annona squamosa (Family: Annonaceae) were screened for antimicrobial and insecticidal activity against the common microbial infestants of pulses and the stored grain pest pulse beetle, Callosobruchus chinensis (Coleoptera: Bruchidae). Flavonoids isolated from aqueous extracts of A squamosa showed antimicrobial activity against all the common microbial contaminants of pulses and 80% insecticidal activity against C chinensis at a concentration of 0.07 mg ml-1. Various physico-chemical tests, chromatographic and spectroscopic studies with partially purified aqueous extract indicated the presence of flavonol type flavonoids. This may provide a useful beginning for the development of botanical pesticides for post-harvest safeguard of pulses.