ANTIOXIDANT AND ANTIMICROBIAL ACTIVITY OF COMMERCIAL GREEN TEA IN CHIANG RAI

Tea antioxidant and antimicrobial properties are affected by various factors, including cultivation area and processing. This work was aimed to investigate antioxidant and antimicrobial activities of green tea (Camellia sinensis var. assamica) products available in Chiang Rai province. Five green tea samples were collected (represented by A, B, C, D, and E). Antioxidant activity of the green tea infusion was evaluated in terms of total polyphenol content (TP) and diphenyl-picrylhydrazyl (DPPH) scavenging activity. Antimicrobial activity against 4 selected pathogens, Staphylococcus aureus, Salmonella typhimurium, Escherichia coli and Listeria monocytogenes, was tested by an agar diffusion method. The active compounds profile in green tea products were evaluated by HPLC. It was found that A provided the highest TP (23.50%), followed by B (20.18%), C (17.40%), D (15.95%) and E (15.86%), respectively. These results are consistent with their anti-oxidation and pathogen inhibitory activities. All teas inhibited gram-positive better than gram-negative bacteria.