Analytical methods for characterization of bile acids and its application in quality control of cow-bezoar and bear bile powder

Bile acids as characteristic compounds of human and animal bile are major endogenous products of cholesterol and play very important roles in cholesterol homeostasis, lipid absorption and production of bile flow. At present, bile acids are useful biomarkers and signaling molecules for the diagnosis or treatment of many diseases in clinic. Various analytical methods, from overall to individual, qualitative to quantitative, have been developed for the determination of bile acids in biomedical samples and even bile-based medicinal materials. The most precious and commonly-used bile-based traditional animal medicines are cow-bezoar (CB) and bear bile powder (BBP), which regard bile acids as the main bioactive constituents and have extensive use for treating many diseases since thousands of years ago. However, extensive consumption of CB and BBP make their natural resource scarcity and price valuableness. Currently, artificial, in-vitro cultured substitutes and even worse adulterants or counterfeits mix in the medicine market and they have seriously compromised the therapeutic effects of these two traditional medicines. To guarantee the long-term development of ethnodrugs, many analytical approaches have been utilized in quality control of CB and BBP. In this paper, various analytical methods of bile acids are summarized and compared with each other.