Abstract
A compound present in normal urine and in ultrafiltrates of uremic plasma in the fraction of so-called "uremic middle molecules" was isolated by liquid chromatography. Preliminary studies, including amino acid analysis, characterization of uronic acids, and ultraviolet spectroscopy, show that the molecule contains glycine, a uronic acid, and an aromatic ring. Characterization by 1H and 13C nuclear magnetic resonance spectrometry shows conclusively that this compound is a double conjugate of glucuronidate--o-hydroxyhippuric acid, which has been previously described by Zimmerman et al., using quite different techniques of isolation and identification (Clin Nephrol 14: 107, 1980; FEBS Lett 129: 237, 1981).