Antioxidant Activities of Hydrolysable Tannins and Flavonoid Glycosides Isolated from Eugenia uniflora L.

A phytochemical investigation of Eugenia uniflora's leaf extract resulted in the isolation of eleven phenolic compounds: 2,3-di-O-galloyl--D-glucose (1), 1,2,3,4,6-penta-O-galloyl--D-glucose (2), gemin D (3), hippomanin A (4), oenothein B (5), eugeniflorin D2 (6), camptothin A (7), afzelin (8), quercitrin (9), myricitrin, (10) and desmanthin-1 (11). These compounds were identified by spectroscopic methods including 1D- and 2D- NMR, UV, IR, and TOF/MS. Compounds 1, 2, 3, 4, 7, 8, 9, and 11 were isolated from this species for the first time. Ten isolates were evaluated for antioxidant activity by DPPH free radical and Oxygen Radical Absorbance Capacity (ORAC-Fluorecein) assay. Dimeric tannins, oenothein B (5), eugeniflorin D2 (6), and camptothin A (7) showed a remarkable radical scavenging capacity.