Phytochemical composition and antioxidant potential of Quercus myrsinaefolia Blume leaf fractions: a combined HPLC and GC–MS approach

Plant-derived phenolic compounds are increasingly recognized for their antioxidant properties and biological activities. However, the relationship between phytochemical composition and antioxidant potential in Quercus myrsinaefolia Blume remains insufficiently understood. In this study, leaf materials were extracted with 80% ethanol and subsequently fractioned into n-hexane, ethyl acetate, and aqueous fractions. Phytochemical profiles were characterized by HPLC and GC–MS analyses, while antioxidant activities were evaluated using DPPH, ABTS, and reducing power assays. Pearson correlation analysis was further performed to investigate the relationships between phytochemical constituents and antioxidant activities. Among all fractions, the ethyl acetate fraction exhibited the strongest antioxidant activity, corresponding to its highest total phenolic (278 mg GAE/g extract) and flavonoid contents (75.1 mg QE/g extract). HPLC analysis revealed that this fraction was enriched in bioactive phenolic acids and flavonoids, including chlorogenic acid, p-hydroxybenzoic acid, myricetin, and kaempferol, whereas the ethanol extract contained a broader but less concentrated phytochemical profile. GC–MS analysis identified diverse metabolites, including phenolics, fatty acid derivatives, and terpenoids, suggesting possible synergistic contributions to antioxidant activity. Pearson correlation analysis further demonstrated that total phenolic and flavonoid contents were strongly associated with antioxidant capacity, whereas condensed tannin content showed comparatively weaker relationships. Overall, these findings demonstrate that antioxidant activity in Q. myrsinaefolia is primarily governed by phenolic composition rather than extraction yield, highlighting the ethyl acetate fraction as a promising natural source of antioxidant phytochemicals for functional food, nutraceutical, and pharmaceutical applications.