Structural and physicochemical properties of microwave-processing pregelatinized maize starch, and its influence on drug release from tablets

Pregelatinized starch (PS) is an important excipient in food and pharmaceutical industry. Microwave technique exhibits advantages of fast setting and high safety in PS preparation, but rarely researches concern on the interaction between PS and active ingredient, which is really important for medicine preparations. In present study, a series PS products were prepared by microwave with gradient-varying starch-water ratio and tableted with the model drug of enalapril maleate. The analyses of morphological, thermodynamic, crystalline and micromeritic properties of PS and of the drug release profile from the obtained tablets exhibited that the destructive effects of microwave on starch granules led the crystallinity decrease and hydrogen bond exposure of starch chains, the compatibility with drug molecules during tableting, and the subsequent drug release inhibition, which were negatively associated with the starch-water ratio in PS preparation. Especially for the sample MT-PS20 prepared from of 2:8 starch-water (w/w), it exhibited as low crystallinity degree as 4.81% and as much as 20% incomplete drug release. This study is expected to provide a basis for the applying of microwave technology on starch modification in pharmaceutical industry.