Influence of lipophilicity in O-acyl and O-alkyl derivatives of juglone and lawsone: a structure–activity relationship study in the search for natural herbicide models

Abstract

Naphthoquinones are known for their broad range of biological activities. Given the increasing demands of consumers in relation to food quality and growing concerns about the impact of synthetic herbicides, it is necessary to search for newagrochemicals. Natural products and allelopathy provide newalternatives for the development of pesticides with lower toxicity and greater environmental compatibility. A structure–activity relationship to evaluate the effect of bioavailability was performed. A total of 44 O-acyl and O-alkyl derivatives of juglone and lawsone with different linear chain lengths were prepared. These compounds were tested on etiolated wheat coleoptiles, standard target species (STS) and four weeds, Echinochloa crus-galli L., Lolium rigidum Gaud., Lolium perenne L. and Avena fatua L. The results showed a strong influence of lipophilicity and, in most cases, the data fitted a logP-dependent quadratic mathematical model. The effects producedwere mostly stunting and necrosis caused by growth inhibition. The potential structure and activity behaviour is described.