Urine 6-tocopherol metabolites

While the angiotensins promote release of aldosterone, the atrial natriuretic hormoner aa cc inhibits release. This group of 21- to 33-residue polypeptides, secreted by cells of the atria (auricles) of the heart, also inhibits release of renin and promotes secretion of both Na+ and water. Thus, they antagonize the action of aldosterone, which promotes Na+ retention. However, there is uncertainty as to the significance of these peptides. The following metabolite of y-tocopherol (Fig. 15-24) has been isolated from urine and is proposed as a new endogenous natriuretic factor.dd... 

The main metabolite of /-tocopherol is 2,7,8-trimethyl-2-(/3-carboxyeth-yl) -G-hydroxychromem (/ -CEHC), which is excreted in the urine. It heis potentially physiologically significant natriuretic activity, whereas the corresponding metabolite of a-tocopherol, which is formed in increasing amounts as intake increases, is inactive (Jiang et al., 2001). 

Tocopherols (vitamin E) occur in many food substances that are consumed as part of the normal diet. The daily nutritional requirement has not been clearly defined but is estimated to be 3.0-20.0 mg. Absorption from the gastrointestinal tract is dependent upon normal pancreatic function and the presence of bile. Tocopherols are widely distributed throughout the body, with some ingested tocopherol metabolized in the liver excretion of metabolites is via the urine or bile. Individuals with vitamin E deficiency are usually treated by oral administration of tocopherols, although intramuscular and intravenous administration may sometimes be used. 

Simon metabolites Initially, two major metabolites of a-tocopherol, the Simon metabolites (tocopheronic acid and tocopheronolactone) were described. Since they have a shortened side chain and an opened chroman structure, they are often quoted to demonstrate the antioxidant function of a-tocopherol in vivo. These metabolites are excreted in the urine as glucuronides or sulfates. The level of these metabolites increases markedly in the urine of healthy volunteers after a daily intake of 2 to 3 g all rac-a-tocopherol. 

In urine, a-tocopherol is excreted after transformation to a-tocopheronic acid, a-tocopheronolactone, and two other acids. Recently, a new metabolite, i.e., a-CEHC (2,5,7,8-tetramethyl-2-(2 -carboxyethyl)-6-hydroxychroman), has been isolated and identified by GC-MS (8,9). 

A Schonfeld, M Schultz, M Petrzika, B Gassmann. A novel metabolite of RRR-a-tocopherol in human urine. Die Nahrung 37 498-500, 1993. 

Blood and urine samples collected over 72 h are analyzed for labeled (d6 and d2) and unlabeled (dO) tocopherols and their metabolites... 

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