Triphenyl derivatives of group IV elements as inhibitors of growth and digestive enzymes of Tribolium castaneum larvae

Abstract

The potency of triphenyl derivatives of group IV elements in inhibiting the growth of first and fourth instar Tribolium castaneum larvae is much greater for Ph 3SnCl and Ph 3PbCl than for Ph 3GeCl, Ph 3SiOH, and Ph 3CCl. Pupated larvae emerge normally, showing that the pupal stage is not affected. The larval growth retardation may result from an antifeeding effect involving digestive enzyme inhibition. Ph 3SnCl and Ph 3PbCl at 500 μmol/kg of diet completely inhibit larval growth (fourth instar larvae) and provide a reduction of 56–59, 29–33, and 2–15% in the in vivo activity of invertase, amylase, and protease, respectively. Under these conditions Ph 3GeCl, Ph 3SiOH, and Ph 3CCl are essentially inactive. High concentrations (5 × 10 −4 and 2 × 10 −3 M) of Ph 3SnCl and Ph 3GeCl acting in vitro strongly inhibit invertase, amylase, and protease activities, whereas Ph 3PbCl is moderately inhibitory and Ph 3SiOH and Ph 3CCl are inactive. When both in vivo and in vitro findings are considered, Ph 3SnCl is the most potent inhibitor of larval digestive enzymes.