1996 Volume 1996 Issue 83 Pages 21-28
Eighty-five samples of commercially available Japanese green teas were assayed for caffeine and the following eight catechins;epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECg), epigallocatechin gallate (EGCg), catechin (C), gallocatechin (GC), catechin gallate (Cg), and gallocatechin gallate (GCg). The tea samples were derived from the following types of tea; Gyokuro, Matcha, Sencha, Bancha, Hojicha, Kamairisei tamaryokucha, and Mushisei tamaryokucha. The total catechin content ranged from 9 to 18% except Hojicha and the caffeine content ranged from 2 to 4% of dry tea leaf. Four major catechins, EC, EGC, ECg, and EGCg, and caffeine were found in nearly all of tea, although some of the Hojicha samples did not have quantititative levels of EC. In addition, four catechins, C, GC, Cg and GCg, were detected in some samples.
Gyokuro and Matcha, both of which are produced from leaves grown under a sunshade, contained more caffeine and less catechins compared to the other types of teas. In general, the higher grade teas contained more caffeine and the lower grade teas contained more catechins. More than half of total catechins contented in the teas was EGCg. The combined contents of EGC and EGCg comprised approximately 80% of total catechin content regardless of the tea type. The level of the free type catechins, EC and EGC, was less than half of the contents of ester type catechins, ECg and EGCg, in Sencha and the tamaryokuchas and less than one-third of ester type catechins in Gyokuro and Matcha. The level of catechins was much lower in Hojicha tea than in the other six types and the catechins composition was also different;probably due in part to the roasting of the tea during processing.