Flavonoid isolation and larvicidal activity of extractives from <i>Hymenolobium petraeum</i>

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