Abstract

This study was aimed at evaluating antibacterial and antioxidant activity of tannins extracted by several solvents from agricultural by-products, including green tea waste and acorn, chestnut, and persimmon hulls. Tannin content was the highest in acetone extracts from all types of hulls, but not green tea waste (p<0.05). Tannin extracts from green tea waste had higher antibacterial activity than those from acorn, chestnut, and persimmon hulls extracted with distilled water, ethanol, or acetone. With ethanol extraction, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity of green tea tannin extracts was significantly higher than that of tannins extracted from acorn, chestnut, and persimmon hulls (p<0.05). In particular, tannins extracted from green tea waste had a greater IC₅₀ value for DPPH scavenging activity than did vitamin C. Antioxidant activity was also significantly higher in ethanol extracts from green tea waste than in distilled water and acetone extracts (p<0.05). Therefore, tannins extracted from green tea waste could be a natural source for substitutes to present antioxidants as well as antibiotics.

Key words: Acorn, antibacterial activity, antioxidant activity, chestnut, green tea, persimmon.