New Iridoid Glucosides from Caryopteris incana (Thunb.) Miq. and Their α-Glucosidase Inhibitory Activities

In our continued investigations of the plant , five new iridoid glucosides - , including two -isomers, and , along with six known compounds - , were isolated from the -butyl alcohol ( -BuOH) soluble fraction of whole dried material of . Their structures were established by a combination of spectroscopic techniques, including 1D and 2D NMR and high resolution electrospray ionization mass spectroscopy (HR-ESI-MS). Furthermore, all isolates were evaluated for their yeast α-glucosidase inhibitory effects. Among these compounds, - and exhibited potent inhibition of α-glucosidase.