Prospecção de metabólitos de anonáceas ativos para Spodoptera frugiperda e Tetranychus spp.

Abstract

The objective of this study was to evaluate the bioactivity fractions soluble in dichloromethane, derived from methanolic extracts from plants of the Annonaceae family to Spodoptera frugiperda and Cuban populations of Tetranychus urticae and Tetranycus tumidus, and perform a chemical prospection of the most active fraction. The stem bark fraction of Duguetia lanceolata was the most active for S. frugiperda, causing high mortality rates. Thus, an exploratory analysis of this plant‟s metabolite profile was conducted using hydrogen nuclear magnetic resonance (1H NMR). Subsequently, a multivariate analysis using partial least squares (PLS) regression, was performed with the input variables: chemical displacements, intensity of the signals obtained by 1H NMR and biological activity for S. frugiperda. The chemical displacements possibly responsible for the biological activity was distinguished and, employing uni and bidimensional RMN experiments, we inferred that the possible substance responsible for the biological activity was the 2,4,5-trimethoxystyrene. Furthermore, the fractioning the soluble fraction of the D. lanceolata stem bark into dichloromethane was conducted by means of silica gel column chromatography of the flash type, layer chromatography and high performance liquid chromatography (HPLC), which allowed the isolation of a mixture containing trans-asarone + 2,4,5-trimethoxystyrene and seven other substances. Among the isolated substances, two of them plus the mixture of trans-asarone + 2,4,5-trimethoxystyrene, had bioactivity evaluated for S. frugiperda. It was noted that the trans-asarone + 2,4,5-trimethoxystyrene mixture was responsible for the biological activity against S. frugiperda larvae. The biological assay with the isolated substances, trans-asarone and 2,4,5-trimethoxystyrene, revealed that both are active for S. frugiperda larvae, however the 2,4,5-trimethoxystyrene is the most active substance, which corroborates the results found in the metabolomics analysis. It was also noted that the insecticidal effect of these substances for S. frugiperda is possibly given via feeding deterrence. Regarding the T. tumidus and T. urticae trials, the fraction soluble in dichloromethane of the D. lanceolata stem bark was also the more active, however, the activity was more pronounced for the T. urticae mite. Analyses by gas chromatography-mass spectrometry (GC-MS) confirmed that the major constituents of the D. lanceolata stem bark fraction are trans-asarone + 2,4,5-trimethoxystyrene.