Saponins from leaves of Kalopanax septemlobus (Thunb) Koidz-Structures of kalopanax-saponins La, Lb and Lc

Hederagenin, delta-hederin [hederagenin alpha-L-arabinoside], kalopanax-saponin A [hederagenin 3-O-alpha-L-rhamnosyl(1-->2)-alpha-L- arabinoside], kalopanaxsaponin I [hederagenin 3-O-beta-D-xylosyl(1-->3)-alpha-L- rhamnosyl(1-->2)-alpha-L-arabinoside], and sapindoside C [hederagenin 3-O-beta-D-glucosyl(1-->4)-beta-D-xylsyl (1-->3)-alpha-L-rhamnosyl(1-->2)-alpha-L-arabinoside] were isolated from stem bark of Kalopanax pictus Nakai (Araliaceae). Among glycosides of hederagenin, disaccharide (kalopanaxsaponin A, commonly also called alpha-hederin), trisaccharide (kalopanaxsaponin I), and tetrasaccharide (sapindoside C) showed significant cytotoxicity on several types of tumor cells, while hederagenin itself exhibited only weak cytotoxicity and its monosaccharide (delta-hederin) was non-cytotoxic. From these results, it suggests that the arabinosyl moiety at C-3 blocks the activity of hederagenin and the position of the second sugar for glycoside linkage is also important for cytotoxicity. In the in vivo experiments, kalopanaxsaponin A (15 mg/kg, i.p.) apparently increased the life span of mice bearing Colon 26 and 3LL Lewis lung carcinoma, as well as cisplatin (3 mg/kg, i.p.). These results indicated that kalopanaxsaponin A has potential anti-tumor applications.