Abstract: The effects of seven alkaloids from Sophora alopecuroids, a leguminous plant, on metabolic esterases of the larvae of the diamondback moth Plutella xylostella (L.) were studied. The results indicate that cytisine and aloperine could inhibit carboxylesterase activity through non-competitive inhibition. Sophoramine, sophoradine, matrine, oxymatrine and cytisine could inhibit the activity of acid phosphoresterase, and cytisine could also weakly inhibit the activity of alkaline phosphoresterase. In addition, three alkaloids, cytisine, sophramine and sophocarpine could inhibit the activity of glutathione-stransferase in diamondback moth larvae.

Key words: Sophora alopecuroids, alkaloids, pesticide, metabolic esterase, Plutella xylostella