Quantitative determination of urinary neuraminyl oligosaccharides by gas-liquid chromatography

Abstract

A gas-liquid chromatographic (GLC) method has been developed for determination of urinary neuraminic acid containing oligosaccharides (N-OS). The procedure involves quantitative isolation of N-OS as a group by successive chromatography on Dowex 50 and Dowex 1 columns. After the neuraminic acid of N-OS has been selectively split by mild acid hydrolysis, the resulting neural “core” oligosaccharides are isolated by chromatography on Dower 1 and analyzed by GLC as their trimethylsilyl derivarives using melibitol as internal standard. Qualitative analysis showed that the “core” mixture consists mainly of three disacharides, lactose (derived from 6-neuraminyl- N-acetyllactosamine), and 3β-galactosyl- N-acetylgalactosamine (derived from mono- and dineuraminyl-3β-galactosyl- N-acetylgalactosamine), while the amount of other oligosaccharides is negligible. GLC quantiation of these disaccharides indicated that neuraminyllactose was the major component of urinary N-OS with the average excretion of 19.4 mg/24 h in males and 16.1 mg/24 hr in females (the amount of N-OS was calculated assuming one neuraminate residue per oligosaccharide). The corresponding values for neuramilynl- N-acetyllactosamine were 12.2 and 8.6 mg/24 hr and for neuramilyl-3-β-galactosyl- N-acetylgalactosamine 2.7 and 2.2 mg/24 hr, respectively. Urinary excretion of these compounds was relatively constant, with a daily variation less than 10% of the mean. The type of diet appeared to have a no influence on urinary N-OS, whereas caloric restriction was followed by a marked fall in the N-OS excretion, which was especially pronounced in the output of neuroaminyllactose.