Urinary excretion of 2,7, 8-trimethyl-2-(beta-carboxyethyl)-6-hydroxychroman is a major route of elimination of gamma-tocopherol in humans.

Little is known of the post-absorptive, metabolic fate of g -tocopherol, the major form of vitamin E in North American diets. The objective of this study was to deter- mine the extent of urinary excretion of 2,7,8-trimethyl-2- ( b -carboxyethyl)-6-hydroxychroman ( g -CEHC), a recently identified metabolite of g -tocopherol. A method for measurement of urinary g -CEHC was developed, using gas chromatography-mass spectrometry (GC-MS) with a deuterated internal standard, 2,7,8-trimethyl-2-( b -carboxy- ethyl)-(3,4- 2 H 2 )-6-hydroxychroman (d 2 - g -CEHC). This stan- dard was synthesized by dehydrogenation of 6-acetyl- g - CEHC followed by deuteration of the resulting 3,4-double bond. The use of d 2 - g -CEHC resulted in accurate determi- nations of the concentration of d 0 - g -CEHC in human urine. Urine samples containing added d 2 - g -CEHC were treated with b -glucuronidase, extracted with an organic solvent, and analyzed by GC-MS. Analysis of 24-h urine pools from healthy subjects revealed g -CEHC concentrations, normal- ized against creatinine, ranging from 2.5 to 31.5 m mol/g creatinine, or a total of 4.6 to 29.8 m mol per day. These re- sults correspond to 2-12 mg g -tocopherol excreted daily as g -CEHC in the urine. Given an estimated mean intake of g - tocopherol of 20 mg/day, catabolism of g -tocopherol to g -CEHC, followed by glucuronide conjugation and urinary excretion, is a major pathway for elimination of g -toco- pherol in humans.— Swanson, J. E., R. N. Ben, G. W. Burton, and R. S. Parker. Urinary excretion of 2,7,8-trimethyl-2-( b - carboxyethyl)-6-hydroxychroman is a major route of elimi- nation of g -tocopherol in humans. J. Lipid Res. 1999. 40: 665-671.