Biflavanones, Chalconoids, and Flavonoid Analogues from the Stem Bark of <i>Ochna holstii</i>

Abstract

Two new biflavanones (<b>1</b> and <b>2</b>), three new bichalconoids (<b>3</b>-<b>5</b>), and 11 known flavonoid analogues (<b>6</b>-<b>16</b>) were isolated from the stem bark extract (CH₃OH-CH₂Cl₂, 7:3, v/v) of <i>Ochna holstii</i>. The structures of the isolated metabolites were elucidated by NMR spectroscopic and mass spectrometric analyses. The crude extract and the isolated metabolites were evaluated for antibacterial activity against <i>Bacillus subtilis</i> (Gram-positive) and <i>Escherichia coli</i> (Gram-negative) as well as for cytotoxicity against the MCF-7 human breast cancer cell line. The crude extract and holstiinone A (<b>1</b>) exhibited moderate antibacterial activity against <i>B. subtilis</i> with MIC values of 9.1 μg/mL and 14 μM, respectively. The crude extract and lophirone F (<b>14</b>) showed cytotoxicity against MCF-7 with EC₅₀ values of 11 μg/mL and 24 μM, respectively. The other isolated metabolites showed no significant antibacterial activities (MIC > 250 μM) and cytotoxicities (EC₅₀ ≥ 350 μM).