Inhibition of glutathione S-transferases (GSTs) activity from cowpea storage bruchid, <i>Callosobrochus maculatus</i> Frabiricius by some plant extracts

Abstract

Crude ethanolic extracts of Tithonia diversifolia, Cyperus rotundus and Hyptis suavolens have insecticidal activity against Callosobrochus maculatus Frabiricius. The ethanol extracts of the plants have positive results for alkaloids, saponin, tannins and flavonoids. Antioxidant and reducing properties were also determined in the crude ethanol extracts. Cowpea storage bruchid, C. maculatus glutathione S-transferases was a potential target for the plants extracts. Gluathione S-transferase from
cowpea storage bruchid was purified by affinity gel chromatography of glutathione sepharose. Inhibition effect of the plant extracts on the GST was studied by spectrophotometric method. The binding of the extract was competitive by the Dixon plot with Ki of 84, 132 and 180 ug/mL for T.
diversifolia , C. rotundus and H. suavolens, respectively. We suggest that reported efficacy of the extract is due to the antioxidant properties and competitve binding inhibition on GST may contribute to the pharmacological basis of the efficacy against cowpea storage bruchid, C. maculatus Frabiricius and its attendant managements.