α-Glucosidase inhibitor from the seeds of balsam pear (Momordica charantia) and the fruit bodies of Grifola frondosa

α-Glucosidase inhibitory activities were found in aqueous methanol extracts of the seeds of Momordica charantia and the fruit bodies of Grifola frondosa. An active principle against the enzyme prepared from rat small intestine acetone powders was isolated and characterized. The structure of the isolated compound was identified as D-(+)-trehalose by FDMS, 1H-, 13C-NMR, and [α]D measurements. The inhibitory activity of trehalose was compared with 1-deoxynojirimycin. Trehalose showed 45% inhibitory activity at the concentration of 2×10−3 M, but 1-deoxynojirimycin had 52% inhibitory activity at 1×10−7 M.