Figure 7. Oatp1a1-null mice had higher hippuric acid, but lower indole-3-carboxylic acid-glucuronide in urine than WT mice.

Structural elucidations were performed based on accurate mass measurement and MS/MS fragmentations of hippuric acid (a) and indole-3-carboxylic acid-glucuronide (b) in urine of WT and Oatp1a1-null mice. By comparison of the retention time in the same MS/MS chromatograph window between authentic standards and urine samples, hippuric acid (c) and indole-3-carboxylic acid-G (d) were confirmed. The authentic standard indole-3-carboxylic acid-glucuronide (indole-3-carboxylic acid-G) was enzymatically synthesized from indole-3-carboxylic acid.