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.

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-beta-D-glucopyranosyl-(25S)-5 alpha-furostane-2 alpha,3 beta,22 zeta,26-tetraol 3-O-[beta-D-xylopyranosyl (1 --> 6)]-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)- 5 alpha-furostane-2 alpha,3 beta,22 zeta,26-tetraol 3-O-[beta-D-xylopyranosyl (1-->6)]-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)-5 beta-furostane-3 beta,22 zeta,26-triol 3-O-[beta-D-xylopyranosyl (1 --> 6)]-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25R)-5 beta-furostane-3 beta,22 zeta,26-triol 3-O-[beta-D-xylopyranosyl (1-->6)]-beta-D-glucopyranoside, 26-O-beta-D-glucopyranosyl-(25S)-5 alpha-furostane-3 beta,22 zeta,26-triol 3-O-[alpha-L-rhamnopyranosyl(1 --> 2)]-beta-D-glucopyranoside, and 26-O-beta-D-glucopyranosyl-(25R)-5 alpha-furostane-3 beta,22 zeta,26-triol 3-O-[alpha-L-rhamnopyranosyl (1 --> 2)]-beta-D-glucopyranoside, respectively.