Preparation of icariside II from icariin by enzymatic hydrolysis method.

It has been reported that icariin and icariside II, two flavonoid glycosides coming from herba epimedii, which have a closely structural relationship, show some pharmacological effects such as preventing osteoporosis, cancer and depression. The content of natural icariside II is very low in herba epimedii, but it is the main component in vivo after the administration of herba epimedii. More icariside II can be obtained from icariin by enzymatic hydrolysis method than by traditional isolation method. This study focuses on finding a simple and feasible method to prepare icariside II from icariin by enzymatic hydrolysis, so as to meet the request for further pharmacologic actions study. Icariin was obtained successively with 90% ethanol extraction, isolation on macroporous resin and purification on silica gel chromatography. Enzymatic hydrolysis conditions were tested for the bioconversion of icariin into icariside II by orthogonal array design. The structures of isolated icariin and produced icariside II were identified by UV, IR, ESIMS, (1)H NMR, (13)C NMR, and DEPT spectroscope. Enzymatic hydrolysis experiment showed that icariin could be transformed into icariside II with the action of beta-glucosidase and the optimum reaction conditions were determined as follows: 50 degrees C, 0.2 M disodium hydrogen phosphate and citric acid buffer system (pH6.0), the ratio of icariin/enzyme is 1:1 and reaction time 5 h. By using this enzymatic condition, 95.5 mg icariside II (with the purity of 99.1%) was obtained eventually by transforming 200 mg icariin.