Separating and identifying multiple structural isomers of 3-hydroxy-3-(3′-hydroxyphenyl)propanoic acid (3,3′-HPHPA)

3-hydroxy-3-(3′-hydroxyphenyl)propanoic acid (CID: 102959) (3,3'-HPHPA) is one of several phenolic molecules that are generated by a process involving gut microbiota and have been implicated in autism and schizophrenia. The structural isomers of 3,3′-HPHPA have been challenging to separate chromatographically. Accordingly, their distribution across brain and other compartments in humans and experimental animals remains poorly characterized. We describe a modified liquid chromatography mass spectroscopy method for the detection and separation of seven commercially available structural isomers of 3,3′-HPHPA. We used the method to screen different compartments in the mouse and demonstrate its utility in identifying multiple structural isomers and conjugates of 3,3′-HPHPA in biological matrices. Characterizing the diversity and complexity of this family of structural isomers will advance studies of their bioactivity and clinical relevance.