Full Length Research Paper

Antioxidant tannins from Syzygium cumini fruit

Liang Liang Zhang and Yi Ming Lin*

Department of Biology, School of Life Sciences, Xiamen University, Xiamen 361005, China.

Key Laboratory of Ministry of Education for Coastal and Wetland Ecosystems, Xiamen 361005, China.

*Corresponding author. E-mail: linym@xmu.edu.cn. Tel.: +86 592 2187657.

Accepted 13 February, 2009

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.

Key words: Syzygium cumini, tannins, antioxidant activity, MALDI-TOF MS, HPLC.