Changes in the Components and Antioxidant Activity of Liubao Tea during Gastrointestinal Digestion
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Abstract:
Changes in the concentration of the main phenolic compounds and their antioxidant capacities in raw and aged Liubao tea during gastrointestinal digestion were evaluated in this study. Ethyl acetate, an extract of the aged Liubao tea, was used as a control. The results indicated that differences in the composition of Liubao tea during the production process led to changes in antioxidant activity. Before digestion, the amount of gallic acid (GA) in raw tea was relatively high, whereas high caffeine content was observed in aged tea. After digestion, the concentrations of the main phenolic compounds (GA, protocatechuic acid, procyanidins, epigallocatechin 3-gallate (EGCG), gallocatechin 3-gallate (GCG), and epicatechin 3-gallate (ECG) decreased by 80~90%, and their antioxidant activities also decreased accordingly. The concentrations of GA, procyanidins, EGCG, ECG, and GCG in the aqueous extract of Liubao tea significantly correlated with their antioxidant activity. In addition, the amounts of procyanidins (0.994) and EGCG (0.997) showed a significant correlation. The percentage of phenols in raw and aged tea were 28.41% and 17.87%, respectively, and their corresponding antioxidative capacities were 16.73 mg/L and 15.37 mg/L, respectively. After digestion, the amount of polyphenols decreased by 68.85% and 69.72%, respectively, and the corresponding antioxidant activities decreased by 88% and 82%, respectively. The aged tea demonstrated better antioxidant activity and a higher ability to maintain antioxidant activity. The substances that most likely affected the antioxidant activities were GA, procyanidins, EGCG, and ECG.
