In vitro Inhibition of Glutathione S-transferases by Several Insecticides and Allelochemicals in Cotton Bollworm, Helicoverpa armigera Hübner

Glutathione S-transferases are a group of enzymes catalyzing the conjugation of reduced glutathione (GSH) with a wide range of xenobiotics bearing electrophilic sites. In insects, GSTs are involved in resistance to insecticides and allelochemicals. In vitro inhibitory effects of several insecticides and allelochemicals on glutathione S-transferases activity in the cotton bollworm, Helicoverpa armigera Hübner, were studied. All organophosphate, carbamate and pyrethroid insecticides tested demonstrated moderate or low inhibiting GST activity toward 1-chlorine-2, 4-ditrobenzo (CDNB). Three allelochemicals (quercetin, tannic acid and rutin) were the most potent inhibitors of the enzymes among all compounds tested. Tannic acid was competitive with CDNB, quercetin was noncompetitive, and rutin was neither competitive nor noncompetitive.