Abstract: Oenothein B(OEB) has strong anti-oxidative and antineoplastic activities.It can be developed into functional health food, food antioxidant and other products.Few researches are done on its application because of a scarcity of nature resources and its low bioavailability.In this article, a method of large scale preparation of OEB from eucalyptus leaves was studied by extracting with ethanol, adsorbing through the macroporous resin, medium pressure column chromatography and preparative liquid phase.The structure of OEB was further identified.In addition, the solubility of OEB was analyzed in different polar solvents.Meanwhile, the loss ratio of OEB was measured by dealing with heating temperature, pH values and enzymes.Finally, the metabolic process of OEB was traced in mice to estimate the stability of OEB in vivo and in vitro comprehensively.The results showed that OEB could be purified by column chromatography and pre-HPLC with the purity of 94.85% and the yield of 2.50% in weight of dried eucalyptus.OEB was easily decomposed with maximum 98.85% by solvents, heating temperature, pH and enzymes with different types and concentration.OEB was disappeared clearly and new components appeared after affecting with plasma in vitro.It was also indicated that OEB was unstable in mice and easy to decompose.It could not be absorbed directly into the blood, and also could not arrive in the feces and urine in the form of prototype compounds.Therefore, OEB is unstable in vivo and in vitro.This result provides theoretical basis for elucidating the metabolic pathway in vivo and in vitro as well as for further study on the improvement of OEB stability.

Key words: Eucalyptus leaves, oenothein B, monomer preparation, stability