[A possible essential metabolite of linoleic acid: lipoic acid, the universal coenzyme of alpha-keto acid oxidation].

The metabolism of [14C-U] linoleci acid (LI) and [14C-U] oleic acid were compared by injecting these fatty acids into growing rats and then homogenizing livers into a three phase system (chloroform/methanol/water). The radioactivities of these phases were equilibrated by extracting them X times with the same solvents. The lipid lower phase was discarded and the analysis was carried out on the evaporated hydroalcoholic upper phase. The residue was extracted again with methanol and hydrolyzed (HCl 6N). The acidic solution was evaporated, treated with HCl/methanol, extracted with chloroform and analysed by thin layer chromatography. One of the most radioactive intermediates detected after injecting LI was purified again and identified as lipoic acid, on the basis of: a. retention time in gas-liquid chromatography; b. Rf in thin layer chromatography; c. molecular weight as determined by mass spectrometry. Thus, the most important fate of essential fatty acids (except for their part in the prostaglandin synthesis and membrane formation) seems to be that of a precursor for this covalently bound alpha keto-acid dehydrogenation coenzyme--the link between lipid and carbohydrate metabolisms.