Expanding the Scope of Targeted Metabolomics by One-pot Microscale Synthesis and Tailored Metabolite Profiling: Investigation of Bile Acid-Amino Acid Conjugates.

Accurate metabolite characterization plays a vital role in targeted metabolomics. Nonetheless, the library of metabolites is still limited, especially for downstream conjugates, and it is time-consuming to synthesize each of these compounds due to high structural diversity. Herein, a green and smart strategy was developed to expand the scope of targeted metabolomics. The reference standards were synthesized in a one-pot microscale reaction, and the analytical method was tailored using the synthetic products. A group of new metabolites, namely bile acid-amino acid conjugates (BA-AAs), was studied as a proof-of-concept. First, in total 160 BA-AAs were synthesized using a small amount (2 mg each) of bile acids and low-toxic reagents within 4 h. Then, an ultra-high-performance liquid chromatography /Orbitrap-MS method was established to comprehensively profile 202 bile acid derivatives in 20 min. Finally, the method was applied to mice with inflammatory bowel disease (IBD) to discover the accumulation of 70 rare BA-AAs in small intestine and liver, where 55 were first reported from biosamples. These BA-AAs are farnesoid X receptor modulators and might contribute to the development of IBD. Our study demonstrated a feasible approach for the broad-spectrum targeted metabolomics of bile acids.