Gymsyloside F and Gymsyloside G, Two New Pregnane Glycosides From the Leaves of Gymnema sylvestre and Their α-Glucosidase and α-Amylase Inhibitory Activities

Two new pregnane glycosides were isolated from the leaves of Gymnema sylvestre (Retz.) R.Br. ex Sm. Their chemical structures were determined as (20S)-12 beta-tigloyloxy-5 alpha-hydroperoxy-3 beta,8 beta,14 beta,17 beta,20-pentahydroxypregn-6-ene 3-O-beta-D-glucopyranosyl-(1 -> 4)-6-deoxy-3-O-methyl-beta-D-allopyranosyl-(1 -> 4)-beta-D-oleandropyranosyl-(1 -> 4)-beta-D-cymaropyranosyl-(1 -> 4)-beta-D-cymaropyranoside (1) and (20S)-12 beta-benzoyloxy-5 alpha-hydroperoxy-3 beta,8 beta,14 beta,17 beta,20-pentahydroxypregn-6-ene 3-O-beta-D-glucopyranosyl-(1 -> 4)-6-deoxy-3-O-methyl-beta-D-allopyranosyl-(1 -> 4)-beta-D-oleandropyranosyl-(1 -> 4)-beta-D-cymaropyranosyl-(1 -> 4)-beta-D-cymaropyranoside (2) on the basis of the extensive spectroscopic methods, including 1D, 2D NMR, HRESIMS, and in comparison with the reported data. At the concentration of 200 mu M, compounds 1 and 2 showed moderate anti alpha-glucosidase and alpha-amylase activities with inhibitory percentage of 31.1 +/- 1.2 and 42.3 +/- 1.7% (for alpha-glucosidase), and 27.8 +/- 1.3 and 34.5 +/- 1.5% (for alpha-amylase), respectively.