Antioxidant activity of phenolic fractions of Mallotus philippinensis bark extract

Phenolic compounds were extracted from Mallotus philippinensi bark using methanol. Six fractions (I-VI) were separated from the extract on a Sephadex LH-20 column using ethanol and acetone-water as the mobile phases and were evaluated for their total antioxidant activity, antiradical activity against DPPH* (2,2-diphenyl-1-picrylhydrazyl radical), and reducing power. The total phenolics and tannin contents in the fractions were determined. The content of total phenolics in the fractions ranged from 54 mg/g (fraction I) to 927 mg/g (fraction VI). Condensed tannins were detected in fractions II-VI. Total antioxidant activity (TAA) of phenolic fractions of Mallotus philipinensis bark extract ranged from 0.58 mmol Trolox/g (fraction I) to 6.82 mmol Trolox/g (fraction IV). Fraction IV also showed the strongest antiradical activity against DPPH* and reducing power. Several phenolic constituents in the fractions were detected by RP-HPLC using a gradient solvent system with UV-DAD detection.