Identification and Biochemical Significance of Substituted Furans in Human Urine

Abstract

Abstract The normal urinary chromatographic pattern on the high-resolution UV-Analyzer exhibits approximately 20 major peaks and more than 100 minor peaks. Three of the major chromatographic peaks, observed in most urinary samples from both normal and pathologic subjects, have recently been identified as 5-hydroxymethyl-2-furoic acid, 2-furoylglycine, and 2,5-furandicarboxylic acid. A related compound, 5-hydroxymethyl-2-furoylglycine, was also identified in the urine of a leukemic patient who was excreting an abnormal amount of the free acid. The compound 5-hydroxymethyl-2-furoic acid and its glycine conjugate have not, to our knowledge, been previously reported in human urine, and the excretion of 2-furoylglycine and 2,5-furandicarboxylic acid by all humans is not generally recognized. The four identified compounds seem to be biochemically interrelated, and a mechanism for their formation from uronic acids is postulated. Analytical techniques and results utilized in the identification of these compounds are discussed. High-resolution (m/Δm ≈ 20,000) mass spectrometric data obtained from three independent laboratories are presented for 5-hydroxymethyl-2-furoic acid, illustrating the accuracy and precision that can be expected for a random sample submitted to a well-equipped facility.