The already known benzoquinone, embelin (mixed with rapanone), and two new benzoquinones, myrsinone and myrsinaquinone, were isolated from the Myrsinaceae plant, Rapanea melanphloes (L), Mez. All the three compounds showed antifeedant activity when bioassayed on nymphs of the desert locust, Schistocerca gregaria (Forsk). They also inhibited growth of second-instar larvae of mosquito Aedes aegypti at low doses, and had acute lethal effects at higher doses.

The efficacy of natural embelin isolated from berries of Embelia ribes Burm. against Tribolium castaneum Herbst is discussed. Embelin mixed with wheat samples at concentrations of 0.1875% and above exhibited high efficacy by bringing about adult mortality even after 8 months of storage. Productivity (progeny/adult-day) of the test insect was also reduced significantly in treatments as compared to controls at different intervals of storage. After 8 months of storage, significant reduction in F1, progeny at the lowest concentration was mainly due to larvicidal action of embelin. In the present study, embelin did not exhibit any chemosterilant action or contact toxicity to adult beetles. Germination of wheat treated with embelin even at the highest concentration of 0.750% was not impaired to any significant extent.