Catechin and caffeine content of tea (Camellia sinensis L.) leaf significantly differ with seasonal variation: A study on popular cultivars in North East India

Two thirds of the tea growing area of North East India is covered by Tocklai vegetative (TV) cultivars. The present study investigates the principal catechins [(−)-epigallocatechin gallate (EGCG), (−)-epicatechin gallate (ECG), (−)-epigallocatechin (EGC), (−)-epicatechin (EC), and (+)-catechin (+C)], total catechin (TC) and caffeine content in thirty-one TV cultivars (TV1-TV31) and four popular cultivars, viz. Betjan, Kharijan, S.3A/3, and T.3E/3 in three harvesting seasons i.e., pre-monsoon, monsoon and autumn, along with their genetic diversity. The monsoon harvested crop showed the highest average content of TC, EGCG, ECG, and caffeine. The TC levels varied from 129 ± 0.03 to 214 ± 4.72, 151 ± 4.21 to 238 ± 8.41, and 121 ± 4.45 to 181 ± 5.82 mg g-1 in pre-monsoon, monsoon and autumn, respectively. The most predominant catechin EGCG varied from 52.2 ± 1.07 to 111 ± 1.24, 70.4 ± 1.03 to 141 ± 1.35, and 58.4 ± 2.47 to 108 ± 2.15 mg g-1in pre-monsoon, monsoon and autumn, respectively. Caffeine content varied from 27.1 ± 0.32 to 48.7 ± 0.50, 35.3 ± 1.56 to 55.0 ± 1.34 and 27.6 ± 1.11 to 40.7 ± 0.42 mg g-1 in pre-monsoon, monsoon and autumn, respectively. TC contents in cultivars TV23, TV17 and TV15; and EGCG contents in TV10, TV11, and TV9 were significantly higher (p ≤ 0.05) than for other cultivars. Environmental factors, viz. day length, sunlight, temperature across seasons might have induced seasonal variation in phenolic composition.