Three unusual norlignans with anti-inflammatory from the resin of <i>Styrax tonkinensis</i> (Pierre) Craib ex Hart

Three unusual phenylisopentane norlignans, designated styraxolanes A-C (<b>1</b>-<b>3</b>), alongside three known analogues (<b>4</b>-<b>6</b>), were obtained from the <i>Styrax tonkinensis</i> resin. Structural assignment was achieved through comprehensive spectroscopic analysis (IR, HRESIMS, 1D- and 2D-NMR). With IC₅₀ values of 7.51 and 8.99 µM, compounds <b>3</b> and <b>4</b> correspondingly exhibited significant suppression of nitric oxide (NO) production in LPS-stimulated macrophages. In contrast, compounds <b>1</b> and <b>2</b> displayed considerably weak activity (IC₅₀ = 23.47 and 24.78 μM, respectively). These results suggest a clear structure-dependent bioactivity. This study expands the chemical diversity of bioactive constituents in Styrax species and provides potential candidates for anti-inflammatory agent development.