Secondary metabolites from neotropical Annonaceae: screening, bioguided fractionation, and toxicity to Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae).
Annonaceae species are interesting sources of structurally diverse compounds with insecticidal properties. Therefore, a screening assay was conducted on ethanolic extracts prepared from the leaves, branches, and seeds of different Annonaceae species (Annona cacans Warming, Annona montana Macfadyen, Annona mucosa Jacquin, Annona reticulata Linnaeus, Annona sylvatica A. St.-Hil., and Duguetia lanceolata A. St.-Hil.) to detect promising sources of compounds with action against Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). The ethanolic extract from A. mucosa seeds (ESAM) was the most active treatment, causing significant acute toxicity (LC50=842.9 mg kg-1) and pronounced larval growth inhibition (EC50=580.4 mg kg-1) after 7 days of exposure to an ESAM-treated diet. Furthermore, ethanolic extracts (at 1000 mg kg-1) from seeds of A. cacans, A. montana, A. mucosa, and A. sylvatica; leaves and branches of A. reticulata; and D. lanceolata leaves only caused sublethal effects, reducing the S. frugiperda larval weight. Nevertheless, ESAM (at LC90) showed an efficacy similar to that of two commercial insecticides of natural [azadirachtin + 3-tigloylazadirachtol (Azamax® 1.2 EC)] and synthetic [chlorantraniliprole (Premio® 20 SC)] origins, which were tested at the registered concentration for S. frugiperda control. Thus, using different chromatographic techniques, bioguided fractionations were conducted and led to the isolation of acetogenin bis-tetrahydrofuran rolliniastatin-1, which was identified as the primary compound from the most active fractions of ESAM. This compound, which caused both strong mortality and pronounced growth inhibition to S. frugiperda, may be a useful component for the integrated management of this important pest species.