Compounds from and the activity to suppress α-glucosidase.

was extensively used to control blood sugar in diabetes treatment in tradition Chinese medicine. In the present study, three new compounds, including an iridoid rehmannia A () and two ionone rehmannias B-C (), together with fourteen known compounds (- and -), were isolated from the roots of . The structures of these compounds were determined by physicochemical constants and spectral analysis (1D, 2D-NMR and MS). The effect of on -glucosidase activity was tested . Compounds , , and (IC: 5.0, 3.1, and 6.3 mM) showed moderate activity to suppress -glucosidase relative to acarbose (IC = 3.0 mM). The findings provided some new insights to understand the hypoglycemic effect of and the development towards the -glucosidase inhibitor drugs.