Chemical constituents from Solanum glabratum Dunal var. sepicula

In the course of screening program of Saudi plants for potential cytotoxic activity, the methanolic extract of Solanum glabratum Dunal var. sepicula and its different fractions were tested against prostate cancer (PC3) and colon cancer (HT-29) cell lines using the MTT assay. In the present study, three spirostan saponin and a flavonoid glycoside were isolated from the active n-butanol fraction through a bio-guided fractionation approach. Two new saponin glycosides were identified as 23-β-D-glucopyranosyl spirost-5-en-3, 23 diol 3-O-[α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranoside and spirost-5-en-3-ol 3-O-[α-L-rhamnopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→3)]-β-D-galactopyranoside. In addition, two known compounds were also isolated and identified as spirost-5-en-3, 23 diol 3-O-[α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranoside and isorhamnetin-3-O-α-L-rhamnopyranosyl (1 – 6) β-D-glucopyranoside. The structures of the isolated compounds were elucidated based on their MS, one dimensional and extensive two dimensional NMR spectral data. Among the isolated metabolites, compound spirost-5-en-3-ol 3-O-[α-L-rhamnopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→3)]-β-D-galactopyranoside showed the highest cytotoxic activity against both PC3 and HT29 cell lines with IC₅₀ values of 14.8 and 19.5 mg/ml, respectively.

Fig. 1