1.After ethanol precipitation, OPC was separated by ethyl acetate-ligroin system. Content of OPC was determined by normal butyl alcohol-hydrochloric acid method at 546 nm to be over 90%.
2.After ethanol precipitation, OPC was separated by ethyl acetate-ligroin system. Content of OPC was determined by normal butyl alcohol-hydrochloric acid method at 546 nm to be over 90%.