Two new protoflavonoids from <i>Polytrichum commune</i> and their cytotoxicity against human gastric cancer cells

Two novel protoflavonoids, namely 1'<i>S</i>-2',3'-dihydroprotoapigenone (<b>1</b>) and 1'(<i>αS</i>), 4'(<i>αR</i>)-2',3'-dihydroprotoapigenin-4'-<i>O</i>-<i>β</i>-<i>D</i>-glucoside (<b>2</b>), were successfully isolated from <i>Polytrichum commune</i> Hedw. The planar structures were clarified <i>via</i> integrated spectroscopic analysis including 1D and 2D nuclear magnetic resonance. Absolute stereochemistry of compound <b>1</b> was definitively assigned utilising calculated electronic circular dichroism (ECD) spectra and optical rotation (OR) data. Furthermore, cytotoxicity evaluations revealed significant antiproliferative activities against human gastric carcinoma HGC-27 cell, compounds <b>‌1</b>‌ and <b>‌2‌</b> exhibiting concentration-dependent growth inhibition, with IC₅₀ values of 37.68 and 41.11 μM, respectively. Both compounds displayed weak effects on SGC-7901 and BGC-823 cells (IC₅₀ > 100 μM), suggesting selective cytotoxicity profiles.‌.