Antioxidant tannins from Syzygium cumini fruit

Abstract

Hydrolysable and condensed tannins in the fruit of Syzygium cumini were identified using NMR, MALDI-TOF MS and HPLC analyses. Hydrolysable tannins were identified as ellagitannins, consisting of a glucose core surrounded by gallic acid and ellagic acid units. Condensed tannins were identified as B-type oligomers of epiafzelechin (propelargonidin) with a degree of polymerization up to eleven. The antioxidant activity were measured by two vitro models: 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing/antioxidant power (FRAP). Tannins extracted from S. cumini fruit showed a very good DPPH radical scavenging activity and ferric reducing/antioxidant power. The results are promising thus indicating the utilization of the fruit of S. cumini as a significant source of natural antioxidants.