Animal bile is a kind of traditional Chinese medicine, has important physiological significance, and has a unique clinical application value. Ursodeoxycholic acid and chenodeoxycholic acid are two endogenous model bile acid, is important in the bear to oxygen cholic acid in clinical, applied research more fully, chenodeoxycholic acid and ursodeoxycholic acid are epimer, coverage is less, the contrast research of two kinds of material did not see the literatured.Chenodeoxycholic aci and ursodeoxycholic acid there are both differences and inseparable connection, research the two substances in the system, for bile acid drugs research, application and development is of great significance.
Structure, the existence and the basic properties
        Bear bile as the main ingredients of drugs is mainly used in the treatment of liver disease, angina pectoris, lung, eye disease, increase  immunity, etc..In the hydrolysate of bear bile powder, check out the bile acid, oxygen cholic acid, ursodeoxycholic acid and chenodeoxycholic acid, amino acid, cholesterol, trace elements, etc., which ursodeoxycholic acid was first separated from bear bile and is considered to be the peculiar composition of bear bile.

Ursodeoxycholic acid (UDCA) chemical called 3 alpha, beta dihydroxy 7-5 beta cholestane-24-acid, molecular formula C24H40O4, molecular weight of 392.56, single product is white powder.By okayama university Shoda separated from China bear bile and name.Bear bile after filtration drying operations made from bear bile powder, UDCA mainly exists in the form of combined with taurine, cattle sulfonated bear bile acid (TUDCA) to oxygen, free of UDCA rarely.Under physiological conditions, UDCA accounted for less than 2% of the human bile acid, is the third level of hydrophilic bile acid.

Chenodeoxycholic acid (CDCA) is the difference in UDCA 7 beta to the isomer.A chemical called alpha 3, 2 hydroxy - 5 7 alpha beta cholestane - 24 - acid, molecular formula C24H40O4, molecular weight of 392.58, is a kind of white or light yellow needle-like crystal.Primary bile acid CDCA is endogenous, hydrophobic.Found in the goose bile for the first time in 1848, in 1972 the United States, the United Kingdom have reported CDCA can dissolve X-ray transmission of gallstones.CDCA in pharmacopoeia in 1975, China, 2000) is not included in the pharmacopoeia. The existence of chenodeoxycholic acid is widely than ursodeoxycholic acid , in chickens, ducks, geese, pigs, sheep and other animals in the bile, quite a proportion of chenodeoxycholic acid are exist.