[Effects of different drying methods and conditions on anthraquinones and tannins in water extract from Radix et Rhiroma Rhei].

OBJECTIVE: To investigate effects of different drying methods on the content of anthraquinones and tannins in water extract from Radix et Rhiroma Rhei (DHY). METHOD: DHY was dried by freeze drying, vacuum drying, drying under normal press and spray drying respectively until its moisture has been 5%. The content of anthraquinones and tannins of samples by different drying methods was determined and compared with. RESULT: The content of total anthraquinones, free anthraquinones, conjugated anthraquinones and tannins of samples by different drying methods was some different. Samples with freeze drying were highest and samples with drying under normal press at 100 degrees C were low. CONCLUSION: Temperature is an important pole in drying process water extract from Radix et Rhiroma Rhei. In our study water extract from Radix et Rhiroma Rhei was stable under 60 degrees C on the whole and unstable when drying exceed in 90 degrees C.