The potential of natural naphthoquinones as the basis for a new class of pest control agents — an overview of research at IACR-Rothamsted

Two pesticidal naphthoquinones from Calceolaria andina (Scrophulariaceae) both contain a key structural feature not previously investigated in this group of compounds. Structure–activity studies have led to the identification of analogues with commercial levels of activity. The primary mode of action in insects is by inhibition of complex III of the mitochondrial respiratory chain. Species specificity has been attributed to differences in the sensitivities of the target sites and whether the hydroxy group at position 2 is acylated. However, in comparative assays with some commercial insecticides, these compounds exhibited unexpectedly poor dose-transfer to insects from leaf surfaces when formulated as emulsifiable concentrates. Volatilisation and degradation were identified as key factors and performance improved with well-chosen formulations.