Experiments were carried out to evaluate the insect-growth regulatory activities of alkaloids and flavonoids isolated from Peganum harmala and Enterolobium cyclocarpum, respectively. Obtained data indicated that exposure of the 2nd instar larvae of the khapra beetle, Trogoderma granarium to sublethal doses of these phytochemicals (3 mg/kg grains) induced serious effects in the development and normal growth of T. granarium. The effects included extended larval and pupal durations, significant decrease in pupation rate, formation of larval-pupal, pupal-adult intermediates and morphogenitic abnormalities similar to those caused by the conventional insect growth regulators. Such effects ultimately resulted in reduction in F1 progeny. At 3 mg/kg grains, percentages reduction in F1 progeny reached 80.7 and 42.6 in case of flavonoids and alkaloids, respectively. Toxicity assessments on the white albino mice confirmed that flavonoids showed no acute or chronic effects and hence were recommended to be used as grain protectants, while alkaloids of P. harmala should be applied at small concentrations.
Natural products, growth regulators, stored-Trogoderma granarium insects, mammalian safety