Abstract:

【Objective】 The article studies phenoloxidase inhibitors against insect and finds the clues on new target for pest control. 【Method】 The effects of deoxycalyciphylline B and Methyl homosecodaphniphyllate extracted from Daphniphyllum calycinum. on phenoloxidase (PO) of Spodoptera exigua (Hübner) were investigated adopting the microtitrationassay. 【Result】 The results indicated that the two compounds showed different inhibitory effects on the PO and the inhibitor concentrations leading to 50% (IC50) activity lost were estimated to be 2.439 mmol?L-1 for deoxycalyciphylline B and 0.879 mmol?L-1 for methyl homosecodaphniphyllate, respectively. The two compounds were also found to be reversible competitive inhibitors and the Ki values were determined to be 2.051 mmol?L-1 and 1.269 mmol?L-1, respectively. 【Conclusion】 Two alkaloids have better inhibitory activities on the PO. The two compounds or their analogues can be used as the templates to guide the molecular design of enzyme inhibitors. These are important ways looking for new pest control agents.

Key words: Daphniphyllum calycinum, Spodoptera exigua, phenoloxidase, inhibitory kinetics