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

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-3 beta,8 beta,12 beta,14 beta,20-pentahydroxy-(20R)-pregn-5-ene-3-O-beta-D-glucopyranosyl-(1 -> 4)-beta-D-digitaloside (1), 3 beta,8 beta,14 beta,20-tetrahydroxy (20R)-pregn-5-ene-3-O-beta-D-glucopyranosyl-(1 -> 4)-O-beta-D-digitaloside-20-O-beta-D-glucopyranoside (2), 3 beta,8 beta,14 beta,20-tetrahydroxy-(20R)-pregn-5-ene-3-O-beta-D-glucopyranosyl(1 -> 6)-O-beta-D-glucopyranosyl-(1 -> 4)-O-beta-D-digitaloside-20-O-beta-D-glucopyranoside (3), along with the known compounds luteolin 4'-O-neohesperidoside (4), apigenin-8-C-neohesperoside (5), beta-sitosterol (6) and beta-sitosterol glucoside (7). Preliminary studies of the crude methanolic extract and methylene chloride fraction showed inhibitory effects against alpha-glucosidase and pancreatic lipase. Among the isolated compounds, compound 5 showed the most potent alpha-glucosidase inhibition with IC50 value of 0.82 +/- 2.50 mu M compared to acarbose (0.81 +/- 0.86 mu M). Whereas compound 1 showed the highest inhibitory activity on pancreatic lipase with an IC50 value of 23.59 +/- 2.49 mu M compared to orlistat (7.41 +/- 2.26 mu M).