Comparative Analysis of Total Phenols, Total Flavonoids, Antioxidant Capacity, and Xanthine Oxidase Inhibition in Six Types of Tea

Tea (Camellia sinensis L.) is a traditional plant and consumed as a beverage or medicinal drink. Camellia sinensis teas exhibit in vitro xanthine oxidase (XOD) inhibitory activity. The total phenols, total flavonoids, antioxidant capacity, and inhibitory effect on the XOD activity of 101 tea extracts were systematically analyzed. The total phenol content of green tea was 158.58 ± 4.15 mg gallic acid equivalents/g, and the total flavonoid content was 122.24 ± 4.17 mg rutin equivalents/g. The total phenol (75.36 ± 9.86 mg gallic acid equivalents/g) and flavonoid (62.95 ± 6.76 mg rutin equivalents/g) contents of dark tea were two-fold lower than those of green tea (p < 0.05). The antioxidant capacity of green tea was 494.32 ± 12.41, 434.88 ± 13.20, 614.99 ± 21.87, and 257.81 ± 8.56 mg Trolox equivalents/g as 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric ion reducing antioxidant power (FRAP), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid(ABTS), and total reducing capacity, respectively. The antioxidant capacity of the dark tea group was the lowest. Black tea showed the numerically highest average XODi activity, while no significant difference in XODi activity was detected among green, yellow, and black teas (p > 0.05). The XOD inhibitory effect was positively correlated with total phenol, total flavonoid, and antioxidant capacities, revealing the relationship among tea polyphenols, antioxidant capacity, and XOD inhibition rate. Principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) showed that green tea had a strong antioxidant capacity and inhibitory effect on XOD. These findings provide an in vitro screening reference for tea resources with antioxidant and xanthine oxidase inhibitory activities, and further studies on key component identification and in vivo validation are warranted.