Polyphenols from longan seeds and their radical-scavenging activity

Five previously uncharacterised polyphenols, ethyl gallate (2) 1-beta-O-galloyl-D-glucopyranose (3), methyl brevifolin carboxylate (4), grevifolin (5) and 4-O-alpha-L-rhamnopyranosyl-ellagic acid (8), and three previously identified polyphenols, gallic acid (1), corilagin (6) and ellagic acid (7), were isolated from longan seed. Their structure were identified by spectrscopic and chemical methods with SC50 values of 0.80-5.91 mu g/ml and towards superoxide radicals with SC50 values of 1.04-7.03 mu g/ml. The radical-scavenging activity of the newly characterised polyphenols was comparable to that of gallic acid, corilagin and ellagic acid. (C) 2009 Elsevier Ltd. All rights reserved.