Rhamnus intermedia Steud. et Hochst. – a New Source of Bioactive Phytochemicals

Antioxidant capacity and various classes of phenolic antioxidants were quantified in leaf and bark methanol extracts of a medicinal plant, Rhamnus intermedia Steud. et Hochst., whose phytochemical composition is unknown. Three well-established assays were used to determine the antioxidant potency of the extracts: the Ferric Reducing/Antioxidant Power assay (FRAP), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay, and 2, 2´-azinobis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) assay, as well as oxygen radical absorbance capacity (ORAC) assay. Total phenol (TP, Folin–Ciocalteu assay), total flavonoid (TF, colorimetric assay with AlCl3) and free phenolic acid (UPLC-MS/MS) content of extracts was quantified. In comparison to bark extracts, leaf extracts exhibited significantly higher TP and TF contents, as well as higher antioxidant capacity according to all four assays. Ten free phenolic acids were quantified in leaf extracts while six were detected in bark extracts. The most abundant phenolic acid in leaves was vanilic acid (1647.06±79.35 μmol/g DW) while salycilic acid was the most concentrated in the bark (111.10±14.14 μmol/g DW).