Synthetic as compared with natural vitamin E is preferentially excreted as alpha-CEHC in human urine: studies using deuterated alpha-tocopheryl acetates.

Alpha-CEHC (2,5,7,8-tetramethyl-2(2'-carboxyethyl)-6-hydroxychroman) is a urinary vitamin E metabolite with a truncated phytyl tail. To test whether natural and synthetic vitamin E are similarly converted to alpha-CEHC, 6 humans consumed 150 mg each RRR-alpha-[5-(C2H3)]- and all rac-alpha-[5,7(C2H3)2]-tocopheryl acetates (d3RRR-alpha- and d6all rac-alpha-tocopheryl acetates, respectively). Plasma was collected at 0, 6, 12 and 24 h; urine (24 h) at 0, 1, 2, 3, 4 and 8 days. Following dosing, plasma was enriched with d3RRR-alpha-tocopherol, while urine was enriched with alpha-CEHC derived from d6all rac-alpha-tocopherol. Thus, synthetic compared with natural vitamin E is preferentially metabolized to alpha-CEHC and excreted.