Impact of the Season on Total Polyphenol and Antioxidant Properties of Tea Cultivars of Industrial Importance in Northeast India

Tocklai vegetative (TV) cultivars are extensively planted in the tea-growing regions of Northeast India. The present investigation explores the impact of season on the total polyphenol (TP) content and the antioxidant activity of thirty-one TV cultivars (TV1–TV31) and four other commercially popular cultivars, namely, Betjan, Kharijan, S.3A/3, and T.3E/3. The TP content of the cultivars was observed to be highest in the monsoon season, with values ranging from 230.57 to 283.53 mg g(−1). In the pre-monsoon season and autumn, the TP content ranged from 197.87 to 256.77 mg g(−1) and from 169.97 to 223.50 mg g(−1), respectively. Antioxidant activity was measured through DPPH, ABTS, FRAP, and lipid peroxidation inhibition assays. The cultivars showed the highest antioxidant activity in the monsoon in tandem with TP content. A bivariate correlation indicated a highly significant (p ≤ 0.01) positive correlation of antioxidant activity with TP content (R(2) = 0.83–0.96).