Inhibitory effects of Schiff analogs of salicylidene aniline on phenoloxidase from Pieris rapae L. (Lepidoptera: Pieridae)

Abstract

In order to gain insight into the development of insecticides with novel modes of action, the effects of salicylidene aniline (a), salicylidene-4-chloroaniline (b), salicylidene-4-bromoaniline (c), and salicylidene-4-nitroaniline (d) on partially purified phenoloxidase (PO) from Pieris rapae L. were investigated. The results showed that the 4 compounds could inhibit PO activity, and the inhibitor concentrations leading to a loss of 50% activity (IC50) were estimated to be 0.025 mmol L-1, 0.732 mmol L-1, 0.471 mmol L-1, and 0.675 mmol L-1, respectively. Meanwhile, all the inhibitors showed reversible competitive inhibition, except (d), which showed reversible mixed inhibition. The KI values were determined as 0.106 mmol L-1, 10.059 mmol L-1, 8.390 mmol L-1, and 20.198 mmol L-1 for the four compounds, respectively. The UV-vis spectra of (a) and (d) in the presence of copper ions and the enzyme showed that (a) could directly chelate the copper ions of PO; however, (d) could neither chelate the additional copper ions nor the copper ions of PO. © 2008.