Isolation and structure elucidation of a highly haemolytic saponin from the Merck saponin extract using high-field gradient-enhanced NMR techniques

Saponins SAPO50 and SAPO30, of which SAPO50 is highly haemolytic, have been isolated from the commercial Merck Saponin. Their structures have been determined exclusively by high-field gradient-enhanced NMR methods. The 1H and 13C NMR spectra of these saponins in pyridine-deuterium oxide have been assigned by homonuclear and heteronuclear correlation experiments. Anomeric configurations were obtained by combined use of J CH, 3 J H-1,H-2, and 1D-NOESY data. Sugar residues were identified by use of 3 J HH values obtained from their subspectra recorded using an optimized 1D-z-TOCSY sequence. Linkage assignments were made using the ge-HMBC and 1D-NOESY spectra. This study shows that SAPO50 represents a hitherto undescribed saponin with the following structure: 3-O-β- d-xylopyranosyl-(1 → 3)-[β- d-galactopyranosyl-(1 → 2)]-β- d-glucuronopyranosyl gypsogenin 28-O-(6-deoxy-β- d-glucopyranosyl)-(1 → 4)-[β- d-xylopyranosyl-(1 → 3)-β- d-xylopyranosyl(1 → 4)]-α- l-rhamnopyranosyl-(1 → 2)-β- d-fucopyranoside. SAPO30, however, corresponds to a saponin previously described [D. Frechet, B. Christ, B. Monegier du Sorbier, H. Fischer, and M. Vuilhorgne, Phytochemistry, 30 (1991) 927–931. Saponin SAPO50 has been isolated from the commercial Merck Saponin and its structure has been determined exclusively by high-field gradient-enhanced [Display omitted]