Isolation and evaluation of the antioxidant activity of phenolic constituents of the Garcinia brasiliensis epicarp

A new glycosylated biflavonone, morelloflavone-4′″-O-β-d-glycosyl, and the known compounds 1,3,6,7-tetrahydroxyxanthone, morelloflavone (fukugetin) and morelloflavone-7″-O-β-d-glycosyl (fukugeside) were isolated from the epicarp of Garcinia brasiliensis collected in Brazil. The structures of these compounds were established using 1H and 13C NMR, COSY, gHMQC and gHMBC spectroscopy. The compounds exhibited antioxidant activity. The greatest potency was displayed by morelloflavone (2), with IC50 = 49.5 mM against DPPH and absorbance of 0.583 at 400 μg/mL for the reduction of Fe3+. The weakest potency was displayed by 1,3,6,7-tetrahydroxyxanthone (1), with IC50 = 148 mM against DPPH and absorbance of 0.194 at 400 μg/mL for the reduction of Fe3+.