Oleanolic saponins

Some oleanolic acid-type saponins were known to exhibit similar hepatoprotective activity [4, 7, 32, 42, 43, 44-46]. We also reported the hepatoprotective activity of Palustroside in which has a glucosyl carboxy group at C-28 [47]. As a part of our continuing study, we examined the preventive effects of five oleanolic acid-type glucuronides (90-95), Fig. (8), isolated from Dumasia tnmcata (Table 3) [48]. 

Fig. (8). Oleanolic-Acid Type Saponins Obtained from Dumasia truncata...

Furthermore, since one of the saponins showed strong cytotoxicity in these experiments, we also examined the cytotoxicity toward hepatocytes without antiserum. Moreover, from the standpoint of the structure-hepatoprotective and -hepatotoxic relationships for the carboxyl group at C-28, oleanolic acid 3-Oglucuronide (96) and oleanolic acid 28-Oglucoside (97) were prepared and tested. 

The information that the hydroxy group at C-29 reduced activity was similar to that on the structure-hepatoprotective relationship. In contrast, the sugar moiety in the E-ring enhanced anti-complementary activity. Further, we tested some oleanolic acid-type glucuronic acids. Although bisdesmosidic saponins showed moderate anti-complementary activity, a monodesmosidic saponin (9 4) showed cyototoxicity. 

Among these, saponins isolated from the rhizome of Panax japonicus and the fruit of Kochia scoparia (that contain approximately 20% of saponins) have been demonstrated to possess gastroprotective properties. Some oleanolic acid oligoglycosides, extracted from P. japonicus and K. scoparia, showed protective effects on ethanol- and indomethacin-induced gastric damage. Moreover, a methanol extract of P. japonicus rhizome was demonstrated to possess protective activity also on stress- or HCl-induced ulcers. The protective activities of all these active saponins are not due to inhibition of gastric acid secretion but probably due to activation of mucous membrane protective factors. 

Sun, J, Han, X, Yu, B, S3mthesis of atypical A-acetylglucosamine-containing saponin, oleanolic acid 3-yl a-L-arabinopyranosyl-(l — 2)-a-L-arabinopyranosyl-(l — 6)-2-acetamido-2-deoxy- 3-D-gluco-pyranoside, Carbohydr. Res., 338, 827-833, 2003. 

From the roots of B. rigidum five new saponins have been isolated and identihed, of which three were saikosaponins, two related to saikogenin F and one to saikogenin D. One of them was also foimd in the aerial parts. Two saponins were related to oleanolic acid. Trivial names of sandrosaponins VII-X wrae given to them. 

The isolated triterpenoid saponins were found to be either of the saikosaponin type or the oleanolic acid type. Ten triterpenoid saponins were monodesmosidic, with a sugar chain at the C-3 position of the aglycone. A bidesmosidic saponin (sandrosaponin IX) showed sugar chains at C-3 (ether linkage) and also at C-28 (ester linkage). 

Preliminary structure-activity relationship studies on triterpene saponins have shown the best activity against HSV-1, -2, adenovirus (AD-2), polyovirus (PV-2) and VSV for saponins having as aglycones ursolic acid, glycyrrhetinic acid, hederagenin and oleanolic acid [152],... 

Some saponins have been reported to present potent sedative activity. Namely, two jujubogenin -3-O-glycosides from Colubrina asiatica [211] and oleanolic acid glycosides from Cussonia barteri significantly inhibited the spontaneous motility of the mice even at low doses (lmg/kg) [212]. The colubrinosides showed an antagonistic effect on amphetamine and exerted a synergistic activity on chlordiazepoxide [211]. 

Yoshikawa, M. "Bioactive Saponins and Glycosides VI... The Structure-Requirement in Oleanolic Acid Glucuronide-Saponins for the Inhibitory Activity," Chem Pharm Bulletin, 1996 Vol, 44 (10), PP. 1915-1922. 

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