Characterization of α -Glucosidase Inhibitor/Cyclodextrin Complex Prepared by Freeze-Drying.

Miglitol (MT) is an α -glucosidase inhibitor with a postmeal blood glucose level lowering effect that is used to treat type 2 diabetes. In addition, α -cyclodextrin ( α CD) has been reported to inhibit increases in postmeal blood glucose. The aim of this study was to prepare a freeze-dried product (FD) composed of MT and α CD or γ CD (molar ratio of MT/ α CD = 1/1, MT/ γ CD = 1/1) and to evaluate the physicochemical properties and biological activity of the FD. The PXRD profile of FD exhibited a halo pattern, and characteristic peaks derived from MT, α CD, and γ CD were not observed. The TG-DTA results for FD indicated an increased weight loss temperature and the absence of an endothermic peak for MT. The NIR absorption spectrum measurement suggested an intermolecular interaction between MT and α CD or γ CD in the FD. 1 H-1 H NOESY NMR spectroscopy (D2 O) revealed an intermolecular interaction in the FD. The results of the α -glucosidase activity inhibition test and the α -amylase activity inhibition test indicated that the FD exhibited the same inhibition rate as MT alone and the effects of MT were not altered by the freeze-drying method.