New isoflavones from the leaves of Vatairea guianensis Auble

Four isoflavones were isolated from Vatairea guianensis Auble leaves and identified as 5,3'-dihydroxy-4'-methoxy-2,2-dimethylpyrano-(5,6:8,7)-isoflavone (1), 5,7-dihydroxy-3',4'- methylenedioxy-8-prenyl-isoflavone (2), 5,3'-dihydroxy-4'-methoxy-7-O-β-glucopyranoside-8- prenyl-isoflavone (3) and derrone (4) together with five triterpenes identified in mixture, lupeol, a-amyrin, β-amyrin, germanicol and betulinic acid. Substances 1-3 are novel natural products, although 1 and 2 have been cited as synthetic products. However, all these compounds are first reported from this species. Their chemical structures were elucidated based on their 1D and 2D nuclear magnetic resonance (NMR) data and high resolution mass spectrometry. The ethanol extract from the leaves and 1-3 were evaluated for their potential in scavenging DPPH* (2,2-diphenyl-1- picrylhydrazylradical) and the results showed that the extract presented high activity (IC50 = 6.2 ± 0.4 μg mL-1), while the isolated compounds showed low antioxidant power (IC50 ≥ 29.5 ± 2.5 μg mL-1) when compared to Trolox (IC50 = 4.5 ± 0.4 μg mL-1). (author)