Inclusion complex of nateglinide with sulfobutyl ether β-cyclodextrin: Preparation, characterization and water solubility

Due to the poor solubility of nateglinide (NTG), its application was seriously limited. In this paper, a novel inclusion complex of nateglinide with sulfobutyl ether β-cyclodextrin (SBE7-β-CD) was synthesized by freeze-drying method, aiming to improve its properties. The phase solubility study was performed to obtain the stoichiometry and stability constant. Then, the solid inclusion complex was characterized by means of FT-IR, DSC, PXRD, SEM, 1H and 2D NMR. The results showed that nateglinide embedded into the cavity of SBE-β-CD from the secondary face partly, forming an inclusion complex with a 1:1 stoichiometry. The stability constants at different temperatures (27, 37, and 50 °C) were 2940 M−1, 2607 M−1, 2156 M−1, separately. Moreover, the NTG-SBE-β-CD inclusion complex displayed higher aqueous solubility compared with free NTG, suggesting its potential application in medicine.