Saponins in Alfalfa (Medicago sativa L.) Root and Their Structural Elucidation

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Abstract
Twenty-four saponins have been identified in alfalfa roots, including 13 medicagenic acids, 2 zanhic acids, 4 hederagenins, 1 soyasapogenol A, 2 soyasapogenol B's, 1 soyasapogenol E, and 1 bayogenin glycoside. Ten of the identified compounds, including 3-O-[β-d-glucopyranosyl(1→3)-β-d-glucopyranosyl]-28-O-β-d-glucopyranoside medicagenate, 3-O-[α-l-rhamnopyranosyl(1→2)-β-d-glucopyranosyl(1→2)-β-d-glucopyranoside] medicagenic acid, 3-O-[β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl]-28-β- d-glucopyranoside medicagenate, 3-O-[β-d-glucuronopyranosyl methyl ester]-28-O-[β-d-xylopyranosyl(1→4)-α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside] medicagenate, 3-O-[α-l-rhamnopyranosyl(1→2)-β-d-galactopyranosyl(1→2)-β-d-glucuronopyranosyl]-21-O-α-l-rhamnopyranoside soyasapogenol A, 3-O-[β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl(1→2)glucopyranosyl]-28-O-[β-d-xylopyranosyl(1→4)-α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside] medicagenate, 3-O-[β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl(1→2)glucopyranosyl]-28-O-{β-d-xylopyranosyl(1→4)-)-[β-d-apiofuranosyl-(1→3)]- α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside} medicagenate, 3-O-[β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl]-28-O-[β-d-xylopyranosyl(1→4)-α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside] zanhic acid, 3-O-[β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl(1→2)-β-d-glucopyranosyl]-28-O-{β-d-xylopyranosyl(1→4)-[β-d-apiofuranoside-(1→3)]- α-l-rhamnopyranosyl(1→2)-α-l-arabinopyranoside}zanhic acid, and 3-O-[β-d-galactopyranosyl(1→2)-β-d-glucuronopyranosyl]-28-O-β-d-glucopyranoside bayogenin, were not reported before, and their structures were established by spectral (FAB-MS and NMR) techniques. In addition, 3-O-[α-l-rhamnopyranosyl(1→2)-β-d-galactopyranosyl(1→2)-β-d-glucuronopyranoside] soyasapogenol E was identified in the roots for the first time. Keywords: Medicago sativa; alfalfa; saponins; triterpenoid glycosides