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Vigna unguiculatais an important source of proteins and energy for humans and animals. However, postharvest losses caused by Callosobruchus maculatuscan reach from 20 to 100% of stored seeds. In this study, the insecticide potential of compounds extracted from Himatanthus drasticuslatex was assessed. The latex was extracted with ethanol (70%) and then partitioned through sequential use of hexane and chloroform. These fractions were investigated by chromatography to determine their chemical composition. Plumieride, identified in a hydroalcoholic subfraction, was tested for insecticidal activity against C. maculatus. The ethanolic fraction (LC50= 0.109; LC90= 0.106%) and the plumieride (LC50= 0.166; LC90= 0.167%) were lethal to larvae. Plumieride (0.25%) delayed larval development, and mortality reached 100%. Its inhibitory action on intestinal α-amylase from larvae was higher (89.12%) than that of acarbose (63.82%). Plumieride (0.1%) inhibited the enzyme α-amylase in vivo in the larval intestine. This result was confirmed by a zymogram test performed by SDS-PAGE when the enzyme electrophoresed on gel copolymerized with starch. When spread on seeds, the hydroalcoholic fraction (1.0%) reduced infestation. The loss of seed mass was 5.26% compared to the control (44.97%). The results confirm the effect of latex compounds in protecting stored seeds against weevil infestation.

Conventional one-dimensional NMR methods and two-dimensional shift-correlated NMR experiments (COSY, HMQC, HMBC) were used for ¹H and ¹³C chemical shift assignments of two naphthoquinone dimers tectol and tecomaquinone I isolated from Lippia sidoides. Copyright © 1999 John Wiley & Sons, Ltd.

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