Isolation and chemical structures of two new catechins from fresh tea leaf.

Catechins are major constituents of the tea leaf (approximately 30% of the dry weight)1* and of considerable importance because these compounds are responsible for astringency in the tea infusion.To understand the contribution of the catechins to tea taste in more detail it is necessary to know the varieties and amounts of catechins present in tea.In this paper I wish to report two catechins newly found in fresh tea leaf.Young tea leaf of cultivar Benihomare (700g, harvested in Aug. 1980) was homogenized in 80% acetone and the homogenate was filtered.The filtrate was concentrated to dryness and dissolved in water.The aqueous solution was extracted with chloroform to eliminate caffeine and then with methylisobutylketone.The combined methylisobutylketone extracts were concentrated and freezedried, from which the crude catechin fraction was prepared by wet diethyl ether extraction.The freeze-dried crude catechin fraction eontained mainly six catechins, EC, +C, EGC, +GC, ECGand EGCG.All evaporations in the study were carried out under reduced pressure in a nitrogen atmosphere.