Phytochemical characterization and in vitro antioxidant properties of endemic Quercus vulcanica bark

The bark of the endemic Kasnak oak (Quercus vulcanica) was analyzed to determine its phytochemical composition, including total phenolic, flavonoid, and condensed tannin contents, as well as its antiradical and reducing antioxidant properties. The results showed a high yield of hydroethanolic extract (17.4%), with a moderate total phenolic content of 420 mg GAE/g extract. Flavonoid and condensed tannin contents were substantial, reaching 179 mg/g extract and 90 mg/g extract, respectively. In vitro antioxidant assays demonstrated strong activity, with notably high DPPH values of 635 mg TE/g extract, while Fe (III)-reducing capacity was moderate to high (2.6 mM/g extract). Q. vulcanica bark differed from that of other oak species in its higher extract content and elevated FRAP antioxidant activity. Principal component analysis revealed positive correlations among flavonoid, total phenolic, and condensed tannin contents. These findings demonstrated Q. vulcanica bark as a promising source of bioactive compounds.