Comparative Analysis of Substance Content, Antioxidant and α-Glucosidase Inhibitory Activity of Each Component of Yaan Tibetan Tea after Water Extraction and Alcohol Precipitation

In order to study the distribution of components (aqueous extract, alcohol precipitation and supernate) in the water extract of Tibetan tea after alcohol precipitation, the basic components, total polyphenols, total flavonoids, and tea pigments were comprehensively analyzed and compared. The contents of polyphenols were detected by high performance liquid chromatography, and the differences of DPPH · and ABTS⁺ · scavenging abilities and inhibitory effects on α-glucosidase digestive enzyme were investigated. Results indicated that the contents of total sugar (17.73 g/100 g), total polysaccharide (16.93 g/100 g), amino acid (5.89 g/100 g) and the abrownin (49.18 g/100 g) in the alcohol precipitation were significantly higher than those in the supernatant. However, the contents of total polyphenols (195.93 mg/g), total flavonoids (61.61 mg/g) and main polyphenols (GA, GC, EGC, C, CA, EC, EGCG, GCG, ECG and CG) in the supernatant were significantly higher than those in the alcohol precipitation. The results of antioxidant activity and digestive enzyme inhibition activity in vitro showed that the DPPH · and ABTS⁺ · scavenging ability of alcohol precipitate was lower than that of supernatant, while had higher inhibition ability of α-glucosidase. The supernatant of Tibetan tea after alcohol precipitation had strong antioxidant activity, while the alcohol precipitation had strong digestive enzymes (α-glucosidase) inhibition activity.