Comparative pesticidal activity of dichloromethane extracts of<i> Piper nigrum</i> against <i>Sitophilus zeamais</i> and <i>Callosobruchus maculatus</i>

Abstract

Piperine a clinically established pesticide was investigated in the seeds, fruit and leaves of Piper nigrum. The dichloromethane extracts obtained from the parts of the plant were analysed through Thin
Layer Chromatography (TLC) using silica gel-GF 254 impregnated aluminium plate and various solvent system consisting of chloroform : methanol (8:2), (6:4), ethyl acetate : methanol (9:1), and acetone :
hexane (6:4) mixtures showing Rf value of 0.95 corresponding to the standard piperine. In all parts of the plants investigated, acetone : hexane solvent system showed distinct Rf value of 0.95
corresponding to the standard piperine. 0.289 mg/ml, 0.578, 0.868, 1.16 and 1.45 mg/ml concentration of dichloromethane seed extracts were used to carry out the pesticidal activities on both pests. The
results showed that mortality rate on both pests are directly proportional to each equivalent concentration of piperine in the extracts. Pesticidal potency on Sitophilus zeamais was significantly
higher (P<0.05) relative to Callostrobuchus maculatus within 9000 s of exposure period.