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

Three unusual phenylisopentane norlignans, designated styraxolanes A-C (1–3), alongside three known analogues (4–6), were obtained from the Styrax tonkinensis 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 3 and 4 correspondingly exhibited significant suppression of nitric oxide (NO) production in LPS-stimulated macrophages. In contrast, compounds 1 and 2 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.