Quantitative structure-activity studies of pyrethroids

Abstract The lethal and convulsive activities against American cockroaches and the knockdown activity against house flies of a set of meta -substituted benzyl esters of the acid component of kadethrin were measured under conditions in which metabolic factors were eliminated as much as possible. The neuroexcitatory and blocking activities in central nerve cords excised from the cockroaches were measured by an extracellular recording technique. Variations in each activity were analyzed quantitatively by use of physicochemical and structural parameters of the aromatic substituents and by regression analysis. The results indicated that variations in each activity other than neuroblocking activity could be analyzed by the hydrophobicity and steric dimensions of the substituents as well as factors arising from olefinic and ether bondings in particular positions of the substituents. The greater the hydrophobicity and the smaller the dimensions in terms of the length and the maximum width of the substituents, the higher were the activities. The neuroblocking activity decreased with the length of substituents when contributions from the above-mentioned structural factors were eliminated. Variations in the whole-body symptomatic activities were related to those in the neurophysiological activities in addition to the hydrophobic factors. The cockroach symptomatic activities increased with both the neuroexcitatory and blocking activities. The knockdown activity in house flies varied mostly with the neuroblocking activity.