The excretion of m-hydroxyhippuric acid by humans.

The chromatographic behavior of several simple phenolic acids was described recently, and a description of the phenolic acids present in human urine has been given (2). Experiments aimed towards establishing a preliminary identification of many of the urinary acids revealed that several compounds having the characteristics of m-hydroxyphenyl acids are found. These include m-hydroxyhippuric, -benzoic, -phenylacetic, and -phenylpropionic acids, and another acid (Compound 2 (2)) which has many properties corresponding t.o those of m-hydroxyphenyllactic acid. Compound 2, however, has slightly different behavior from synthetic m-hydroxyphenyl-m-lactic acid on chromatograms. Other workers have reported the presence of m-hydroxybenzoic acid in pregnant mare urine (3), rabbit urine (4, 5), and human urine (5), and preliminary chromatographic identifications of m-hydroxyphenylacetic acid (6) and m-hydroxyphenyllactic acid (7) in human urine also have appeared. So far, there have been no reports of the existence of m-hydroxyphenyl compounds in plant sources which might explain the presence of these derivatives in urine. Because of a possible metabolic importance of m-hydroxyphenyl compounds, it was desirable to establish conclusively the identity of the quantitatively important m-hydroxyphenyl acids which occur in human urine. This paper describes the isolation of m-hydroxyhippuric acid from normal human urine, its identification, and some observations relating to its occurrence in urine.