β-cyclodextrin assistant flavonoid glycosides enzymatic hydrolysis

BACKGROUND: The content of icaritin and genistein in herba is very low, preparation with relatively large quantities is an important issue for extensive pharmacological studies. OBJECTIVE: This study focuses on preparing and enzymic hydrolysis of flavonoid glycosides /β-cyclodextrin inclusion complex to increase the hydrolysis rate. MATERIALS AND METHODS: The physical property of newly prepared inclusion complex was tested by differential scanning calorimetry (DSC). The conditions of enzymatic hydrolysis were optimized for the bioconversion of flavonoid glycosides /β-cyclodextrin inclusion complex by mono-factor experimental design. The experiments are using the icariin and genistein as the model drugs. RESULTS: The solubility of icariin and genistein were increased almost 17 times from 29.2 μg/ml to 513.5 μg/ml at 60°C and 28 times from 7.78 μg/ml to 221.46 μg/ml at 50°C, respectively, demonstrating that the inclusion complex could significantly increase the solubility of flavonoid glycosides. Under the optimal conditions, the reaction time of icariin and genistin decreased by 68% and 145%, when compared with that without β-CD inclusion. By using this enzymatic condition, 473 mg icaritin (with the purity of 99.34%) and 567 mg genistein(with the purity of 99.46%), which was finally determined by melt point, ESI-MS, UV, IR, (1)H NMR and (13)C NMR, was obtained eventually by transforming the inclusion complex(contains 1.0 g substrates). CONCLUSION: This study can clearly indicate a new attempt to improve the speed of enzyme-hydrolysis of poorly water-soluble flavonoid glycosides and find a more superior condition which is used to prepare icaritin and genistein.