A new method for the analysis of urinary vitamin E metabolites and the tentative identification of a novel group of compounds

There is currently interest in measuring urinary metabolites of vitamin E, It has been suggested that alpha-tocopheronolactone (alpha TL), with an oxi dized chroman ring, may be an indicator of in vivo oxidative stress and 2,5 ,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman (alpha-CEHC), with a s hortened side chain but intact hydroxychroman ring, may provide a measure o f adequate or excess vitamin E status. To date, methods in the literature h ave tended to concentrate on the estimation of single metabolites. We descr ibe the establishment and validation of a relatively simple and reproducibl e method to extract and quantitate a range of vitamin E metabolites using 0 .5 ml of human urine. The vitamin E metabolites were extracted from urine u sing solid phase extraction cartridges, deconjugated enzymatically, and ana lyzed using gas chromatography-mass spectrometry. Using this method we have identified alpha TL and the CEHC metabolites derived from alpha-, delta-, and gamma-tocopherol, In addition we have tentatively identified a novel gr oup of vitamin E metabolites, which are related to the CEHCs but have three extra carbons in the side chain. The possibility of the artifactual oxidat ion of alpha-CEHC to alpha TL during the assay procedure is also discussed. (C) 2000 Academic Press.