Protective effects of Dioscorea birmanica extract against oxidative stress-induced damage in cultured normal hepatocytes and its phytochemical constituents

Abstract

The rhizome ethanolic extract of Dioscorea birmanica Prain & Burkill (DBE) has long been used as Thai traditional remedies for treatments of chronic diseases whose development is linked to long-term oxidative stress. However, its protective effects against such stress have never been reported. This study evaluated antioxidant actions of DBE using multiple chemical assays and further assessed its protective effects in the normal hepatic BNL CL.2 cell line against sodium nitroprusside (SNP)-induced oxidative stress by measuring cell viability, oxidative damage to biomolecules, and the activities of antioxidant enzymes. Free radical levels in BNL CL.2 cells were determined to verify molecular mechanisms underlying the protective effects of DBE. The contents of phenolics and flavonoids were measured by colorimetric assays, and some of them were structurally elucidated by LC-ESI-QTOF-MS/MS. The results showed that DBE exerted potent scavenging activities against synthetic and natural radicals, including moderate metal chelating activity. Moreover, DBE improved the cell viability, attenuated oxidative damage to lipids, proteins, and DNA, as well as recovered the activities of antioxidant enzymes against SNP-induced oxidative stress with significant degrees in comparison to only stress-induced cells. In parallel with its cytoprotection, DBE exhibited significant reductions of excess levels of intracellular free radicals potentially through its potent antioxidant actions, thereby revealing the protective mechanism of DBE. For phytochemical analysis, high contents of phenolics and flavonoids were detected in DBE using colorimetric assays, and the structures of 14 potential antioxidants were elucidated using LC-ESI-QTOF-MS/MS. Therefore, DBE has the potential to develop into herbal dietary supplements for liver protection.