New pregnane glycosides from Caralluma hexagona Lavranos and their in vitro α-glucosidase and pancreatic lipase inhibitory effects

Abstract

Three new pregnane glycosides in addition to four known compounds were isolated from the methylene chloride fraction of Caralluma hexagona Lavranos using bioassay-guided fractionation. The new compounds were identified as 12,20-di-O-benzoyl-3β,8β,12β,14β,20-pentahydroxy-(20R)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1→4)-β-d-digitaloside (1), 3β,8β,14β,20-tetrahydroxy (20R)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1→4)-O-β-d-digitaloside-20-O-β–d-glucopyranoside (2), 3β,8β,14β,20-tetrahydroxy-(20R)-pregn-5-ene-3-O-β-d-glucopyranosyl-(1→6)-O-β-d-glucopyranosyl-(1→4)-O-β-d-digitaloside-20-O-β–d-glucopyranoside (3), along with the known compounds luteolin 4`-O-neohesperidoside (4), apigenin-8-C-neohesperoside (5), β-sitosterol (6) and β-sitosterol glucoside (7). Preliminary studies of the crude methanolic extract and methylene chloride fraction showed inhibitory effects against α-glucosidase and pancreatic lipase. Among the isolated compounds, compound 5 showed the most potent α-glucosidase inhibition with IC50 value of 0.82 ± 2.50 μM compared to acarbose (0.81 ± 0.86 μM). Whereas compound 1 showed the highest inhibitory activity on pancreatic lipase with an IC50 value of 23.59 ± 2.49 μM compared to orlistat (7.41 ± 2.26 μM).