New steroidal saponins from the bulbs of Lilium brownii var. viridulum

Phytochemical investigation of the bulbs of Lilium brownii var. viridulum led to the isolation of seven new steroidal saponins (1-7), along with eight known analogues (8-15). The new steroidal saponins were identified as 27-O-[(3S)-3-O-β-D-glucopyranosyl 3-methylglutaroyl]isonarthogenin 3-O-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (1), (24S,25S)-3β,17α,24-trihydroxy-5α-spirostan-6-one 3-O-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (2), tenuifoliol 3-O-[β-D-glucopyranosyl-(1→4)]-β-D-glucopyranoside (3), 26-O-β-D-glucopyranosylnuatigenin (4), 26-O-β-D-glucopyranosylnuatigenin 3-O-β-D-glucopyranoside (5), 26-O-β-D-glucopyranosylnuatigenin 3-O-{α-L-rhamnopyranosyl-(1→2)-[β-D-glucopyranosyl-(1→6)]}-β-D-glucopyranoside (6), 26-O-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosylnuatigenin 3-O-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (7), using a combination of spectroscopic evidence and chemical methods. The carbohydrate chain of a sugar linked to C-3 of the HMG group (3-hydroxy-3-methylglutarate) in compound 1 is rarely found in nature. Compound 2 possesses a new (24S,25S)-3β,17α,24-trihydroxy-5α-spirostan-6-one aglycon moiety. The disaccharide chain linked to C-26 hydroxy group of the furospirostanol in compound 7 has not been observed from natural sources.