title: A new steroidal saponin from AGAVE brittoniana and its biphasic effect on the Na+-ATPase activity.
abstract: A new steroidal saponin, 3-{(O-6-deoxy-a-L-mannopyranosyl-(1 --> 4)-O-beta-D-glucopyranosyl-(1 --> 3)-O-[O-beta-D-glucopyranosyl-(1 --> 3)-beta-D-glucopyranosyl-(1 --> 2)]-O-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranosyl)oxy}-6-hydroxy-(3beta,5alpha,6alpha,25R)-spirostan-12-one, was isolated from Agave brittoniana Trel. The structure was determined by extensive NMR spectroscopy studies and chemical conversions. Its effects on the Na+-ATPase and (Na+ + K+)-ATPase activities of the proximal tubule from pig kidney were evaluated. It was observed that this steroidal saponin exerts a biphasic effect on the Na+-ATPase activity. It is concluded that the effect of the aqueous extract as a diuretic is due, at least in part, to the action of saponin on the ouabain-insensitive Na+-ATPase.
authors.affiliation: Núcleo de Pesquisas de Produtos Naturais, Universidade Federal do Rio de Janeiro, Centro de Ciências da Saúde, 21944-970, P.O. Box 68045, Rio de Janeiro, Brasil.
authors.forename: Graziela M
authors.initials: GM
authors.lastname: Silva
authors.forename: Aloa M
authors.initials: AM
authors.lastname: De Souza
authors.forename: Luciene S
authors.initials: LS
authors.lastname: Lara
authors.forename: Tatiana P
authors.initials: TP
authors.lastname: Mendes
authors.forename: Bernadete P
authors.initials: BP
authors.lastname: da Silva
authors.forename: Anibal G
authors.initials: AG
authors.lastname: Lopes
mesh_terms: D027882:Agave / Q000737:chemistry*; D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000201:enzymology; D007684:Kidney Tubules / Q000201:enzymology; D007700:Kinetics; D008745:Methylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D018515:Plant Leaves / Q000737:chemistry; D012503:Saponins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000378:metabolism*; D013256:Steroids / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D013552:Swine
chemical_list: D010936:Plant Extracts; D012503:Saponins; D013256:Steroids; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase