Neurophysiological Effects and Quantitative Structure-Activity Analyses of Insecticidal Silaneophanes

Abstract

Silaneophanes containing a quaternary silicon connected to variously substituted phenyl groups were shown to prolong the sodium residual and tail currents in the crayfish giant axon under voltage clamp conditions, sharing characteristics common to conventional pyrethroids. Insecticidal activity of these compounds was measured against American cockroaches. Variations in the insecticidal activity measured under conditions to inhibit the oxidative metabolic mechanism were analyzed quantitatively. It was found that insecticidal activity was linearly related to the crayfish tail-current prolongation activity when the transport factors of compounds were allowed for by use of a hydrophobicity parameter. The higher the tail-current prolongation activity, the higher the insecticidal activity. Variations in the insecticidal activity were also correlated with physicochemical substituent parameters, indicating that the longer the substituents on the benzene ring, the higher the activity. There was an optimum in the hydrophobicity of the substituents, probably related to factors involved in the transport process.