A new steroidal saponin, 3-{(O-6-deoxy-α-ʟ-mannopyranosyl-(1→4)-O-β-ᴅ-glucopyranosyl-( 1→3)-O-[O-β-ᴅ-glucopyranosyl-(1→3)-β-ᴅ-glucopyranosyl-(1→2)]-O-β-ᴅ-glucopyranosyl-( 1→4)-β-ᴅ-galactopyranosyl)oxy}-6-hydroxy-(3β,5α,6α,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.
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