Estimation of neutral sugars and sugar alcohols in biological fluids by gas-liquid chromatography

The biochemistry, metabolism and inherited defects of the pentose phosphate pathway: a review

The recent discovery of two defects (ribose-5-phosphate isomerase deficiency and transaldolase deficiency) in the reversible part of the pentose phosphate pathway (PPP) has stimulated interest in this pathway. In this review we describe the functions of the PPP, its relation to other pathways of carbohydrate metabolism and an overview of the metabolic defects in the reversible part of the PPP.

Analysis of Concentration and 13C Enrichment of d-Galactose in Human Plasma

Background: A stable-isotope dilution method for the sensitive determination of d-galactose in human plasma was established.

Methods: d-[13C]Galactose was added to plasma, and the concentration was measured after d-glucose was removed from the plasma by treatment with d-glucose oxidase and the sample was purified by ion-exchange chromatography. For gas chromatographic–mass spectrometric analysis, aldononitrile pentaacetate derivatives were prepared. Monitoring of the [MH-60]+ ion intensities at m/z 328, 329, and 334 in the positive chemical ionization mode allowed the assessment of 1-12C-, 1-13C-, and U-13C6-labeled d-galactose, respectively. The d-galactose concentration was quantified on the basis of the 13C-labeled internal standard.

Results: The method was linear (range examined, 0.1–5 μmol/L) and of good repeatability in the low and high concentration ranges (within- and between-run CVs <15%). The limit of quantification for plasma d-galactose was <0.02 μmol/L. Measurements in plasma of postabsorptive subjects yielded d-galactose concentrations (mean ± SD) of 0.12 ± 0.03 (n = 16), 0.11 ± 0.04 (n = 15), 1.44 ± 0.54 (n = 10), and 0.17 ± 0.07 (n = 5) μmol/L in healthy adults, diabetic patients, patients with classical galactosemia, and obligate heterozygous parents thereof, respectively. These data were considerably lower (3- to 18-fold) than the values of a conventional enzymatic assay. The procedure was also applied successfully in a stable-isotope turnover study to evaluate endogenous d-galactose formation.

Conclusions: The present findings establish that detection of d-galactose from endogenous sources is feasible in human plasma and show that erroneously high results may be obtained by enzymatic methods.

Determination of polyol profiles in human urine by capillary gas chromatography

A new rapid capillary gas chromatographic method is described for the profile analysis of urinary polyols as their trifluoroacetyl derivatives. Ten urinary polyols: erythritol, threitol, fucitol, ribitol, arabinitol, xylitol, mannitol, glucitol, galactitol and myo-inositol were completely determined for the first time. Iditol was newly found in normal urine. Urinary polyols were verified by gas chromatography/mass spectrometry.

Capillary gas chromatographic profiling of urinary, plasma and erythrocyte sugars and polyols as their trimethylsilyl derivatives, preceded by a simple and rapid prepurification method

A capillary gas chromatographic method for the profiling of trimethylsilylated mono- and disaccharides and polyols in urine, plasma and unwashed and washed erythrocytes is described. The prepurification method is based on the moderate inhibition of the derivatization experienced in the presence of physiological amounts of inorganic salts and the relative stability of the formed trimethylsilylethers towards treatment with water and dilute hydrochloric acid. Series to series quality control data for 31 sugars/polyols in a pooled urine are given. The method was used to establish age-dependent concentrations of 18 sugars/polyols in urines of 72 control persons on a free diet. Gas chromatographic profiles and quantitative data obtained from urines of pediatric patients with galactosemia treated with a diet low in lactose and galactose, type 1 hereditary tyrosinemia treated with a diet low in phenylalanine and tyrosine, and a neurological disorder with a high calorie gastric drip feeding, are presented and discussed. Examples of the profiling of sugars/polyols in the plasma, unwashed and washed erythrocytes of a healthy adult, and the plasma of a newborn with galactosemia prior to treatment, are given.