Flavonoid isolation and larvicidal activity of extractives from Hymenolobium petraeum

Hymenolobium petraeum (angelim-pedra) is a Fabaceae member valued for robust timber. This study examines the ethyl acetate extract of H. petraeum, focusing on its chemical composition and biological activities. Four compounds, previously unreported in H. petraeum, were identified using ¹H NMR,¹³C NMR and ESI-MS and by comparison with existing literature: anhydrotuberosin (1), sophorocoumestane A (2), coumestrol (3) and daidzein (4). Among these compounds, 4 exhibited significant larvicidal activity against Aedes aegypti larvae, showing 100% mortality at 50 μg/mL and 100 μg/mL concentrations. 1 also displayed notable activity, while 2 and 3 showed no mortality at the tested concentrations. Molecular docking studies targeting the Nobo protein indicated that 2 and 3 possessed more substantial enzyme inhibition potential than 1 and 4, contrasting with the larvicidal assay results. This paradox suggests that 2 and 3 may undergo transformation in aqueous environments or through larval hydrolases, potentially reducing their effectiveness against Nobo.