Chemical Constituents from Suaeda glauca and Their Protective Effects against Dexamethasone-Induced Muscle Atrophy in C2C12 Myotubes

As part of our ongoing efforts to discover biologically active compounds from natural sources, we conducted a phytochemical investigation of Suaeda glauca, a halophytic plant widely distributed throughout Asia.Phytochemical investigation of the water extract of S. glauca led to the isolation of four phenolic compounds (1-4) through semi-preparative HPLC purification.The structures of the isolated compounds were elucidated and identified as N-[2-(4-hydroxyphenyl) ethyl]-N-methylacetamide (1), p-coumaric acid (2), trans-ferulic acid (3), and erigeside II (4) based on comparisons of their spectroscopic and physical data with those reported previously.Notably, this is the first report of compounds 1 and 4 from S. glauca.We further investigated the effects of compounds 1-4 on dexamethasone (Dex)-induced muscle atrophy in C2C12 myotubes.Among the isolated compounds, compounds 1 and 4 significantly attenuated Dex-induced reductions in myotube diameter.Compound 4 exhibited the most pronounced protective effect, increasing myotube diameter from 87.0% in the Dex-treated group to 98.6% and 111.5% at 25 and 50 μM, respectively.Western blot analysis further demonstrated that compound 4 suppressed the Dex-induced expression of the muscle atrophy markers MAFbx and MuRF1 while restoring the expression of MyoD and myogenin.Together, these findings provide morphological and molecular evidence supporting the protective effects of erigeside II (4) against dexamethasone-induced skeletal muscle atrophy.