α-Glucosidase inhibitors from the leaves of Embelia ribes.

A novel and rare 1,4-dehydrated ceramide, embelamide (1), and a new C-glycoalkaloid which is based on a β-carboline ring system, 1-(2'-deoxy-α-d-ribopyranosyl)-β-carboline (4), were isolated from the CHCl3 soluble fraction of the leaves of Embelia ribes (Myrsinaceae), together with thirteen known compounds (2-3, 5-15). Their structures were elucidated on the basis of spectroscopic data. Compounds 1, and 5-12 possessed significant α-glucosidase inhibitory activity in a concentration-dependent manner, and showed more potent inhibitory activity, with IC50 values ranging from 1.3 to 155.0 μM, than that of a positive control acarbose (IC50, 214.5 μM).