Abstract: In order to investigate the phenolic components and in vitro antioxidant activity of the peel and pulp of different plum varieties, we chose nine plum varieties for the extraction of free and bound phenols from the peel and pulp. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity and oxygen radical absorbance capacity (ORAC) of the extracts were determined, and the polyphenol composition was analyzed by high performance liquid chromatography (HPLC). The results showed that total phenolic contents in the peel of nine plum varieties were between 111.52 and 775.88 mg GAE/100 g, and between 120.65 and 301.91 mg GAE/100 g in the pulp. Among the varieties investigated, both the peel and pulp of red plum had the highest phenolic contents, and the lowest phenolic contents were detected in both tissues of prune. Free phenols were more abundant than bound ones in all the varieties, and the main phenolic compounds identified were phenolic acids (protocatechuic acid, chlorogenic acid and caffeic acid). In vitro antioxidant assays showed that the phenolic extracts from all nine plum varieties had some antioxidant activity with IC50 values for scavenging of DPPH radical in the range of 4.38–46.46 μg/mL and ORAC values in the range of 0.24–210.50 μmol TE/g. Among these varieties, free phenols extracted from the pulp of Wushan plum possessed the lowest DPPH radical scavenging capacity and those extracted from the peel of red plum had the highest ORAC value.

Key words: plum, polyphenol, antioxidant activity, high performance liquid chromatography (HPLC)