Bioactive Saponins and Glycosides. XXVI. New Triterpene Saponins, Theasaponins E10, E11, E12, E13, and G2, from the Seeds of Tea Plant (Camellia sinensis)

New triterpene saponins, theasaponins E 10 , E 11 , E 12 , E 13 , and G 2 , were isolated from the saponin fraction of the seeds of Camellia sinesis.Their stereostructures were elucidated on the basis of chemical and physicochemical evidence.During the course of our characterization studies on the bioactive saponin constituents from Camellia species (Theaceae), [1][2][3][4][5][6][7][8][9][10] we have reported the isolation and structure elucidation of 29 saponins such as theasaponins A 1 -A 5 , C 1 , E 1 -E 9 , F 1 -F 3 , H 1 , and G 1 , assamsaponins A-D, F, and I, camelliasaponins B 1 and C 1 , and floratheasaponin A from the seeds of C. sinensis (L.) O. KUNTZE. 1-4Furthermore, theasaponins A 2 , E 1 , E 2 , and E 5 , and assamsaponins A, C, and D, which were isolated from the seeds of C. sinensis and C. sinensis L. var.assamica PIERRE, 6,7 were found to show protective effects on ethanolinduced gastric lesions in rats. 3,4Recently, floratheasaponins A-C with anti-hyperlipidemic activity were isolated from the flowers of C. sinensis. 5As a continuing study on the seeds of C. sinensis, we have isolated five new triterpene saponins, named theasaponins E 10 (1), E 11 ( 2), E 12 (3), E 13 (4), and G 2 (5).This paper deals with the structure elucidation of these new saponins (1-5).The saponin fraction of the methanolic extract of tea seeds (cultivated in Shizuoka prefecture, Japan), which was described previously, 3 was purified by HPLC to give 1 (0.0080%), 2 (0.0080%), 3 (0.0090%), 4 (0.018%), and 5 (0.0080%). Structures of Theasaponins E10 (1), E 11 (2), E 12 (3), E 13 (4), and G 2 (5) Theasaponin E 10 (1), ([α] D 27 +1.7° in MeOH), was isolated as colorless fine crystals of mp 234.1-235.8°C from CHCl 3 -MeOH.The IR spectrum of 1 showed absorption bands at