Medicinal foodstuffs. IV. Fenugreek seed. (1): Structures of trigoneosides Ia, Ib, IIa, IIb, IIIa, and IIIb, new furostanol saponins from the seeds of indian Trigonella foenum-graecum L.

Abstract

Six new furostanol saponins called trigoneosides Ia, Ib, IIa, IIb, IIIa, and IIIb were isolated from a medicinal foodstuff, fenugreek seed, the seed of Trigonella foenum-graecum L. (Leguminosae) originating from India, together with two known saponins, glycoside D and trigofoenoside A. The structures of trigoneosides Ia, Ib, IIa, IIb, IIIa, and IIIb were determined on the basis of chemical and physicochemical evidence as 26-O-β-D- glucopyranosyl-(25S)5α-furostane-2α,3β,22ξ,26-tetraol 3-O-[β-D- xylopyranosyl(1→6)]-β-D-glucopyranoside, 26-O-β-D-glucopyranosyl-(25R)- 5α-furostane-2α-3β,22ξ,26-tetraol 3-O-[β-D-xylopyranosyl (1→6)]-β-D- glucopyranoside, 26-O-β-D-glucopyranosyl-(25S)-5β-furostane-3β,22ξ,26- triol 3-O-[β-D-xylopyranosyl (1→6)]-β-D-glucopyranoside, 26-O-β-D- glucopyranosyl-(25R)-5β-furostane-3β,22ξ,26-triol 3-O-[β-D-xylopyranosyl (1→6)]-β-D-glucopyranoside, 26-O-β-D-glucopyranosyl-(25S)-5α-furostane- 3β,22ξ,26-triol 3-O-[α-L-rhamnopyranosyl(1→2)]-β-D-glucopyranoside, and 26-O-β-D-glucopyranosyl-(25R)-5α-furostane-3β,22ξ,26-triol 3-O-[α-L- rhamnopyranosyl (1→2)]-β-D-glucopyranoside, respectively.