- Tannins and Related Compounds. LXIX. Isolation and Structure Elucidation of B,B'-Linked Bisflavanoids, Theasinensins D-G and Oolongtheanin from Oolong Tea. (2)
-
Chemical examination of the aqueous acetone extract of commercial oolong tea has led to the isolation of four new theasinensins D-G, and a new type of dimeric flavan-3-ol named oolongtheanin, together with previously reported theasinensins A, B, and C.On the basis of chemical and spectroscopic evidence, theasinensins D and E were characterized as atropisomers (4 and 5) of theasinensins A (1) and C (3), respectively, while theasinensins F and G were shown to be B,B'-linked bisflavanoids (6 and 7) consisting of (-)-epicatechin 3-O-gallate and (-)-epigallocatechin 3-O-gallate units, in which the biphenyl bonds possess S- and R-chiralities, respectively.Similarly, oolongtheanin was characterized as a novel metabolite (8), probably derived from theasinensins by oxidation of one of the B-rings.Keywords - oolong tea; Camellia sinensis var. viridis; Theaceae; polyphenol; theasinensin; oolongtheanin; oxidative metabolite; bisflavanoid; flavan-3-ol; fermentation.
- Hashimoto, Fumio,Nonaka, Gen-Ichiro,Nishioka, Itsuo
-
p. 1676 - 1684
(2007/10/02)
-