The aim of this study was to identify antioxidants from Garcinia buchananii bark extract using hydrogen peroxide scavenging and oxygen radical absorbance capacity (ORAC) assays. LC-MS/MS analysis, 1D- and 2D-NMR, and circular dichroism (CD) spectroscopy led to the unequivocal identification of the major antioxidative molecules as a series of three 3,8''-linked biflavanones and two flavanone-C-glycosides. Besides the previously reported (2R,3R,2''R,3''R)-naringenin-C-3/C-8'' dihydroquercetin linked biflavanone (GB-2; 4) and (2R,3S,2''R,3''R)-manniflavanone (3), whose stereochemistry has been revised, the antioxidants identified for the first time in Garcinia buchananii were (2R,3R)-taxifolin-6-C-beta-D-glucopyranoside (1), (2R,3R)-aromadendrin-6-C-beta-D-glucopyranoside (2), and the new compound (2R,3S,2''S)-buchananiflavanone (5). The H(2)O(2) scavenging and the ORAC assays demonstrated that these natural products have an extraordinarily high antioxidative power, especially (2R,3S,2''R,3''R)-manniflavanone (3) and GB-2 (4), with EC(5)(0) values of 2.8 and 2.2 muM, respectively, and 13.73 and 12.10 mumol TE/ mumol. These findings demonstrate that G. buchananii bark extract is a rich natural source of antioxidants.     «

The aim of this study was to identify antioxidants from Garcinia buchananii bark extract using hydrogen peroxide scavenging and oxygen radical absorbance capacity (ORAC) assays. LC-MS/MS analysis, 1D- and 2D-NMR, and circular dichroism (CD) spectroscopy led to the unequivocal identification of the major antioxidative molecules as a series of three 3,8''-linked biflavanones and two flavanone-C-glycosides. Besides the previously reported (2R,3R,2''R,3''R)-naringenin-C-3/C-8'' dihydroquercetin link...     »