Flavanol derivatives with antioxidant activity from the stem bark of Xylocarpus granatum

A new flavanol derivative dihydrocaffeic acid-(3→8)-epicatechin together with two known derivatives, (+)-catechin and catechin-(4β→8)-catechin were isolated from the stem bark of a mangrove plant Xylocarpus granatum. Their structures were established using 1D and 2D NMR experiments as well as HRMS-FAB, EIMS, IR and UV spectra. The compounds were evaluated for DPPH radical scavenging activity and ferric reducing antioxidant power and they exhibited higher activity compared to butylated hydroxytoluene (BHT) which is a commercially available antioxidant. Catechin-(4β→8)-catechin showed the highest DPPH radical scavenging activity with IC50 of 4.5 µg/mL