Tocopherol metabolites 2, 5, 7, 8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman (α-CEHC) and 2, 7, 8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman (γ-CEHC) in human serum after a single dose of natural vitamin E

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Abstract
Backgroundα- and γ-Tocopherol are vitamin E compounds in human blood and tissues. α-CEHC (2,5,7,8-tetramethyl-2-(2'-carboxyethyl)-6-hydroxychroman) and γ-CEHC (2,7,8-trimethyl-2-(2'-carboxyethyl)-6-hydroxychroman) have been identified as water-soluble metabolites which are excreted with the urine in humans. Aim of the study To assess over-time changes of serum levels of α- and γ-CEHC in humans after a single dose of vitamin E from a natural source. Methods Twenty-one healthy subjects ingested a single dose of vitamin E (306 mg of RRR-α-tocopherol and 1.77 mg of γ-tocopherol). Blood was collected before (baseline) and 2, 6, 12, 24, 35, 50, and 74 h after ingestion. Serum was separated and levels of α- and γ-tocopherol and α- and γ-CEHC were determined by HPLC. Results After vitamin E ingestion, a statistically significant increase was observed for α-tocopherol and α-CEHC. Maximum serum levels for both compounds were measured 12 h after application (33.3 ± 11.1 μmol α-toco-pherol /L and 42.4 ± 18.3 nmol α-CEHC /L); baseline values were reached again after 72 h. While γ-tocopherol levels decreased during the study period, an increase in the metabolite γ-CEHC was observed. The optical isomer formed in the metabolism of RRR-α-tocopherol was assigned as S-α-CEHC. Conclusionsα-CEHC levels increase after administration of a single dose of natural vitamin E in humans. The appearance of the metabolite in blood parallels that of the parent compound. The γ-tocopherol analog appears to be metabolized more efficiently than α-tocopherol.

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