The saponin fraction from the seeds of the tea plant [
Camellia sinensis (L.) O. K
UNTZE (Theaceae)] was found to exhibit potent protective effects on ethanol- and indomethacin-induced gastric mucosal lesions in rats. Five new triterpene saponins, theasaponins
E3
(1),
E4
(2),
E5
(3),
E6
(
4
), and
E7
(
5
), were isolated together with 11 known saponins from the saponin fraction. The chemical structures of 1—
5
were elucidated on the basis of chemical and physicochemical evidence. Among the isolated saponins, theasaponins
E1
(
6
),
E2
(
7
), and
E5
(3) and assamsaponin C (10) showed an inhibitory effect on ethanol-induced gastric mucosal lesions at a dose of
5
.0 mg/kg,
p.o. and their activities were stronger than that of omeplazole. With regard to the structure–activity relationships of theasaponins, the following structural requirements for a protective effect on ethanol-induced gastric lesions were suggested; 1) the 21- and/or
22
-acyl groups are essential for the activity, 2) acetylation of the 16-hydroxyl group reduce the activity.
抄録全体を表示