Chemical Composition Difference and in Vitro Activity of Different Varieties of Oolong Tea before and After Roasting
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Abstract:
In order to study the changing trend of mass base and difference in activity of different raw oolong tea materials after roasting, the differences in the contents of total polyphenols, total flavonoids, tea polysaccharides, catechins and caffeine of different raw oolong tea materials before and after roasting were analyzed. In vitro enzymatic biochemical reaction was used to investigate the inhibitory abilities of different oolong tea raw materials and finished products against α-glucosidase, lipase and xanthine oxidase. The results showed that the content of tea polyphenols decreased from 13.75%~15.59% in raw materials to 12.41%~14.14% in the finished products, with the contents of Tieguanyin and Rougui being slightly higher than those of Old Fir Narcissus, Sanyin Narcissus and Dahongpao (P<0.05). The content (mass fraction) of total flavonoids in the raw materials ranged from 0.71% to 1.00%, and the content of total flavonoids in Tieguanyin raw materials was the lowest, which was significantly different from those of other raw materials (P<0.05). Except for Tieguanyin, the contents of total flavonoids in other oolong tea samples were insignificantly different before and after roasting (P>0.05). The contents of tea polysaccharides in the raw materials were 1.14%~1.82%, which increased to 1.64%~2.12% in the finished products after baking. All the samples showed the inhibitory abilities against α-glucosidase, lipase and xanthine oxidase, and the finished products after baking exhibited weaker inhibitory abilities against α-glucosidase and lipase. Rougui showed higher abilities to inhibit α-glucosidase and lipase activities. After roasting, oolong tea had an enhanced ability to inhibit xanthine oxidase, with the IC50 values decreasing from 13.21~17.42 mg/mL to 10.26 mg/mL~14.38 mg/mL for the finished product
