Structural diversity and antioxidant activity of condensed tannins fractionated from mangosteen pericarp

► Tannin-rich fractions with potent antioxidant activity are obtained from mangosteen. ► Highly structural heterogeneity of mangosteen tannin is revealed by LC-MS and TOF-MS. ► Fractionation improves the detection of MALDI-TOF-MS for polymeric condensed tannin. ► Mangosteen condensed tannin with most potent antioxidant activity in 9.27 mDP.