Components, antioxidant and hypoglycemic activities of water extracts from different varieties of raw tea

Abstract

To compare the differences in the active components, the antioxidant and hypoglycemic activities in vitro between seven different varieties of raw tea water extracts, and to determine the correlation between each ingredient and activity, the contents of total polyphenols, total flavonoids and tea polysaccharides in the water extracts of raw tea and its infusion were determined. The antioxidant and hypoglycemic activities of raw tea water extracts were evaluated by DPPH· scavenging ability, ORAC value and α-glucosidase and α-amylase inhibition as indicators, and Pearson correlation analysis was performed. The results were as follows: (1) There were significant differences in the contents of water extract, total polyphenols, total flavonoids and tea polysaccharides among the seven varieties, while the highest contents were found in Golden tea (53.42%±0.14%), Guihong No.4 (40.87%±1.09%), Yunnan big leaf species (27.17%±0.26%) and Fuyun No.6 (2.70%±0.02%), respectively. (2)There were also significant differences in DPPH· scavenging abilities and ORAC values among the seven varieties, while the varieties showing better antioxidant effects in both evaluation methods were the Liupao group species, Guihong No.4 and Wantian species. (3) The inhibitions of α-glucosidase and α-amylase by the water extracts of seven varieties were significantly stronger than those of acarbose positive control. The varieties showing better hypoglycemic effects in both evaluation methods were Liupao group species, Guihong No.4 and Guiqing species. (4)The antioxidant and hypoglycemic activities were all strongly and positively correlated with the contents of total polyphenols and flavonoids. In summary, raw tea quality of Liupao group species, Guihong No.4, Wantian species and Guiqing species are better, among which Liupao group species and Guihong No.4 have the prospect of developing antioxidant and hypoglycemic functional food; Wantian species and Guiqing species have the potential of developing antioxidant and hypoglycemic functional food respectively. Total polyphenols and total flavonoids have a great contribution to the in vitro antioxidant and hypoglycemic activities of raw tea, so that attention should be paid to the protection of such components during the further processing and utilization of raw tea. The results of this study provide a scientific basis for the development of Liupao tea products with better antioxidant and hypoglycemic activities in the selection of raw materials and processing methods of raw tea.

Keywords

• different varieties
• raw tea
• water extract components
• antioxidant activity
• hypoglycemic activity