Extracts of Jatropha curcas L. exhibit significant insecticidal and grain protectant effects against maize weevil, Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract

Phytochemical composition of leaf extracts as well as biological effects of juice, leaf extracts and seed oil of Jatropha curcas against Sitophilus zeamis were examined. The study also investigated the inhibition of oviposition, progeny production and grain damage, insecticidal effects and mammalian toxicity of the extracts. Compared to other phytochemicals, the concentration of saponin and cardiac glycoside were higher in the leaf extract. All extracts of J. curcas (0 – 100 ppm) investigated showed a dose-dependent inhibition of ovisposition, progeny production and promote significant (P < 0.001) insect mortality. Grains pre-treated with seed oil produced the highest result for all the parameters. The seed oil (100 ppm) produced 93% (P < 0.001) protection against grain damage by Sitophilus zeamis. Observable physical deformities were observed in rats administered with graded doses of the seed oil as opposed to other extracts. Administration of a single dose of the extracts produced significant (P < 0.01) elevation of serum level of alanine (ALT) and aspartic (AST) transaminases and alkaline phosphatase (ALP) in rats.