In the search for new secondary metabolites with biopesticidal properties

Secondary metabolites are involved in diverse functions in plants, including defense and protective processes. Information concerning the biosynthesis of secondary metabolites in plants points at a constitutive or induced chemical defense, generated for protection against a variety of phytopathogenic attacks. Our phytochemical studies are aimed at finding biopesticides of botanical origin. Some plant taxa of American distribution are toxic to selected insects, fungi and bacterial strains, and their effect has been associated with the presence of phenolics, phenylpropanoids and terpenes. We have isolated some diterpenes, triterpenes, sesquiterpene lactones, flavonoids, and phenylpropanoids from members of the plant families Araucariaceae, Asteraceae, Calceolariaceae, Celastraceae, and Rhamnaceae. In addition, we have identified a number of chemical derivatives of these compound classes from the plants. A major finding indicates that compounds or their derivatives that possess antioxidant, antifungal, insect growth regulator or insecticidal activity and enzymatic inhibitors are natural compounds. Insecticidal activities were assayed against strains of lepidopteran, dipteran, and coleopteran insect pests that affect many crops. Antifungal and antibacterial activities were assayed against phytopathogenic species of filamentous fungi and bacterial strains that are pests on many crops. Our results indicate that the plant-derived compounds obtained from the abovementioned plants have excellent insect growth regulatory activity and a good potency as antifungal agents. However, little is known about the effects of these natural compounds and their derivatives on insect pests. The natural compounds that we have isolated represent a valuable resource for future studies of plant chemical defense and the role of these substances in chemical ecology.