Two new protoflavonoids from Polytrichum commune and their cytotoxicity against human gastric cancer cells.

Two novel protoflavonoids, namely 1'S-2',3'-dihydroprotoapigenone (1) and 1'(αS), 4'(αR)-2',3'-dihydroprotoapigenin-4'-O-β-D-glucoside (2), were successfully isolated from Polytrichum commune Hedw. The planar structures were clarified via integrated spectroscopic analysis including 1D and 2D nuclear magnetic resonance. Absolute stereochemistry of compound 1 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 ‌1‌ and ‌2‌ 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.‌.