Identification of aromatic dihydroxy acids in biological fluids

Area of Science:

• Analytical Chemistry
• Metabolomics
• Organic Chemistry

Background:

• Human urine contains a complex mixture of metabolites.
• Identifying and characterizing these metabolites is essential for understanding human physiology and disease.
• Dihydroxy aromatic acids are a class of compounds with potential biological significance.

Purpose of the Study:

• To identify and characterize novel dihydroxy aromatic acid metabolites in human urine.
• To synthesize all constitutional isomers of dihydroxy-benzoic, -phenylpropionic, -phenylacetic, and -cinnamic acids.
• To develop mass spectrometry-based methods for distinguishing between these isomers.

Main Methods:

• Gas chromatography-mass spectrometry (GC-MS) analysis of methyl and trimethylsilyl (TMS) derivatives.
• Synthesis of various dihydroxy aromatic acid isomers.
• Analysis of fragmentation patterns in mass spectra.

Main Results:

• 3,5-Dihydroxyphenylpropionic acid, 3,5-dihydroxycinnamic acid, and 2,3-dihydroxycinnamic acid were identified in human urine for the first time.
• Mass spectra of methyl and TMS derivatives provided distinct fragmentation patterns for differentiating constitutional isomers.
• Specific fragmentation pathways were observed for ortho-dihydroxy compounds, 1,2,3-trisubstituted isomers, and 3,5-dihydroxy aromatic acids.

Conclusions:

• The developed mass spectrometry methods enable reliable differentiation of dihydroxy aromatic acid isomers.
• These findings expand the known metabolome of human urine.
• The study provides valuable tools for future metabolomic investigations involving dihydroxy aromatic acids.