Identification of steroidal glycosides from South African Hyacinthaceae species.

Abstract

Steroidal glycosides isolated from natural products have shown great bioactivity and anticancer potential. Previous studies showed that the Ornithogalum genus of Hyacinthaceae family is one of the sources of steroidal glycosides with vast structural diversity. Therefore, in search of cytotoxic steroidal glycosides from South African species, two Ornithogalum plant species were investigated. Phytochemical investigation of Ornithogalum saundersiae Baker bulbs afforded three undescribed steroidal glycosides namely 3-[(β-D-glucopyranosyl)oxy]-22-[α-L-rhamnopyranosyL-(1→2)-β-D-glucopyranosyl)oxy]-16,23-epoxy-23-(2-methyL-1-propenyl) cholestane triglycoside (170), (171), and (172). LC-MS-MS study conducted on bulb crude extract revealed a significant number of unidentified compounds. Liver cell viability assays on O. saunderisae crude extracts and isolated compounds reveal moderate cytotoxicity effects for 171 (IC50 = 25 µg/mL) and 172 (IC50 = 115 µg/mL). Negligible effects were shown for compound 170. Phytochemical investigation of Albuca batteniana Hilliard & B.L.Burtt. resulted in the isolation of one previously known compound named 3-O-β-D-glucopyranosyL-β-sitosterol (175) exhibiting some cytotoxic effects on liver cells (IC50 =275 µg/mL). All the structures of isolates were elucidated by extensive spectroscopic analysis.