Oligoglycosides

Figure 1. The model structure of plant RG-11 [1, 13] with four oligoglycosidic side-chains linked to the homogalacturonan backbone.

Yoshikawa, M., Murakami, T., Ueno, T., Yashiro, K., Hirokawa, N., Murakami, N., Yamahara, J., Matsuda, H., Saijoh, R., and Tanaka, O. (1997b). Bioactive saponins and glycosides. Vlll. Notoginseng (1) New dammarane-type triterpene oligoglycosides, Notoginsenosides-A, -B, -C, and -D, from the dried root of Panax notoginseng (Burk.) F. H. Chen. Chem. Pharm. Bull. 45,1039-1045. 

A pathway (Scheme I) (8.9) for the hydrolysis of oligoglycosides by lysozyme that differs from the previously accepted mechanism (Scheme II) (3,10-12) is described in this section. The alternative pathway, suggested by results of a 55-ps MD simulation of the lysozyme (GlcNAc)e complex (1), is consistent with the available experimental data and with stereoelectronic considerations. Experimental data have demonstrated that Glu 35 and Asp 52 are essential, as shown by recent site-directed mutagenesis results (13.) which corroborate chemical modification studies (3.14 and references cited therein), and that the reaction proceeds with retention of configuration at Ci Q and references cited therein). A fundamental feature of the alternative pathway is that an endocyclic bond is broken in the initial step, in contrast to the exocyclic bond cleavage in the accepted mechanism. 

Murakami and M. Yoshikawa. Structures of new acylated oleanene-type triterpene oligoglycosides, teasaponins E-I and E-2, from the seeds of tea plant. Camellia sinensis (L.) O. Kuntze. Chem Pharm Bull 1998 46(12) 1901-1906. 

D Auria, M.V. Gomez Paloma, L. Minale, L. Riccio, R. Debitus, C. (1992) Structure characterization of two marine tritepene oligoglycosides from a Pacific sponge of the genus Erylus. Tetrahedron, 48,491-8. 

Yoshikawa, M. et al.. New flavonol oligoglycosides and polyacylated sucroses with inhibitory effects on aldose reductase and platelet aggregation from flowers of Prunus mume, J. Nat. Prod., 65, 1151, 2002. 

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. 

Minale, L., Riccio, R., and Zollo, F., Steroidal oligoglycosides and polyhydroxysteroids from echin-oderms, Fortschritte der Chemie Organischer Naturstoffe, 62, 74, 1993. 

De Marino, S., Iorizzi, M., Zollo, F., Minale, L., Amsler, C.D., Baker, B.J., and McClintock, J.B., Isolation, structure elucidation, and biological activity of the steroid oligoglycosides and polyhydrox-ysteroids from the Antarctic starfish Acodontaster conspicuus, J. Nat. Prod., 60, 959, 1997. 

Iorizzi, M., Minale, L., and Riccio, R., Starfish saponins. part 39. Steroidal oligoglycoside sulphates and polyhydroxysteroids from the starfish Asterina pectinifera, Gazz Chim. Ital., 120, 147, 1990. 

Fig. 7.10 Hypothetical structure of RG-II. The figure shows the four oligoglycosidic side chains A-D whose residues are numbered according to the model sequence. Reprinted from Pelleiin et al. (1996), with permission from Elsevier...

Recently, we have reviewed for the first time the chemical structures of sea cucumber glycosides and the principal spectral features of the aglycones and oligosaccharide chains in their H- and C-NMR spectra [55]. Most of these triterpenoid oligoglycosides contain an aglycone... 

Lysozyme hydrolyses oligoglycosides. It is a P-glucosidase that cleaves a P-glucoside bond and releases P-glucose. Although lysozyme was the first enzyme to have its high resolution crystal structure determined (Blake et al. 1965) and the catalysis has been studied for many years, the mechanism is not fully understood and remains a source of discussion (Kirby 1987 Mooser 1992). Two features of the hydrolysis mechanism are unresolved (1) Whether the initial bond-breaking occurs via an... 

Fukuda N, Imamura N, Saito E, Nohara T, Kawasaki T (1981) Steroid Saponins and Sapogenins of Underground Parts of Trillium kamtschaticum Pall. IV. Additional Oligoglycosides of 18-Norspirostane Derivatives and Other Steroidal Constituents. Chem Pharm Bull 29 325... 

---