Iridoid glycosides link with phenylpropanoids from Rehmannia glutinosa

Two new iridoid glycosides link with phenylpropanoids, rehmanniosides G (1) and H (2) along with 11 known compounds, 6-O-(E)-caffeoylajugol (3), 6-O-(E)-feruloylajugol (4), verbasoside (5), jionoside C (6), acteoside (7), leucosceptoside A (8), brachynoside (9), jionoside B1 (10), jionoside A1 (11), isoacteoside (12) and isomartynoside (13) were isolated from the roots of Rehmannia glutinosa (Gaertn.) DC. Their chemical structures were elucidated on the basis of extensive spectroscopic methods, including 1D, 2D NMR and mass spectra. Compounds 7 - 11 showed significant inhibitory α-glucosidase with IC50 values ranging from 261.4 to 408.7 μM (acarbose, IC50 of 204.2 ± 19.9 μM).[Formula: see text].