Comparative study of polyphenol contents, antioxidant activities and cytotoxicity of green tea from three different Asian sources

Abstract

Recently, green tea has become the focus of attention due to its wide range of positive health benefits. Green tea comes from Camellia sinensis (family Theaceae) which is native to Asian countries. In this study, green tea from three different Asian sources namely, Japanese green tea (JGT), Myanmar green tea (MGT) and Thai green tea (TGT) were chosen to be investigated and compared. Total polyphenol contents in the extracts were determined by High Performance Liquid Chromatography (HPLC) assay and the results were observed as 58%, 55% and 54% (w/w) of dry solid weight for JGT, MGT and TGT respectively. The antioxidant activity of green tea extracts was then evaluated by 1,1-dipheny1-2-picrylhydrazyl (DPPH) radical scavenging activity assay and total antioxidant status assay. From the DPPH assay, it was found that all green tea extracts have stronger radical scavenging activity than butylated hydroxytoluene (BHT) with all exhibiting significantly lower effective concentration at 50% inhibition (EC50) on DPPH radical. Total antioxidant status assay was determined by Randox kit method and no significant difference was observed among green tea extracts in terms of mmol/l Trolox equivalent, using Trolox as standard. The cytotoxicity of green tea extracts on melanoma cell line was examined by 3-[4,5-Dimethylthiazol-2yl]-2,5-diphenyl-terazolium bromid (MTT) assay. The cytotoxic effect was significantly difference with JGT having the highest inhibition and showing EC50 at 173 ug/ml followed by MGT (198 ug/ml) and TGT (206 ug/ml).