Jurg Loliger

Chemical evidence for interactions between vitamins E and C

Experimental proof is provided for interactions between radicals of vitamin E/vitamin C as generated by air-oxidized lipids (liquid fraction of subcutaneous chicken fat). Using ESR spectroscopy, hydrogen atom exchange is shown to take place between vitamin C and the radical of vitamin E. Sequential consumption of these two vitamins in oxidized lipid, first vitamin C then vitamin E, is demonstrated by means of differential pulse polarography. These results elucidate the in vitro radical scavenging functions attributed to vitamin E and vitamin C as well as their synergism in lipid antioxidation.

Radical Exchange Reactions between Vitamin E, Vitamin C and Phospholipids in Autoxidizing Polyunsaturated Lipids

Antioxidant reactions of mixtures of vitamin E, vitamin C and phospholipids in autoxidizing lipids at 90 degrees C have been studied by ESR spectroscopy. When the phospholipid contained a tertiary amine (e.g. phosphatidylcholine), the vitamin C and the vitamin E radicals were successively observed as these two vitamins were sequentially oxidised during lipid oxidation. In the presence of the primary amine contained in phosphatidylserine, the vitamin E oxidation was delayed for a few hours. In this case neither the vitamin C, nor the vitamin E radicals but a nitroxide radical derived from the phospholipid was observed. Similar results to those obtained with PS were obtained in the presence of either phosphatidylethanolamine or soybean lecithin. The participation in the radical reactions of phospholipids possessing a primary amine can therefore explain the synergistic effect of these phospholipids in a mixture of vitamins E and C.

Role of free radicals in the mode of action of anthralin.

Radical reactions of anthralin and its metabolites with skin have been studied by ESR spectroscopy. The influence of compounds which are known to suppress inflammation are described. The ESR spectra recorded during the reaction of anthralin with skin were essentially composed of one broad line centered at g = 2.0030. Similar but much weaker spectra were recorded with the dimer and no signal at all was obtained with 9,10-dihydroxyanthraquinone. The ESR response obtained with anthralin was neither affected by the radical scavengers 2-tert-butyl-4-methoxy-phenol (BHA), 2,6-di-tert-butyl-4-methyl-phenol (BHT) dl-alpha-tocopherol, nor by the antiinflammatory agents clobetasol-17-propionate or indomethacin, nor by potassium hydroxide. We infer that anthralin inflammation is not associated with the presence of anthralin-derived radicals in the skin.

The fate of antioxidant radicals during lipid autoxidation II. The influence of oxygen supply on lipid autoxidation

Abstract The influence of oxygen during the reaction of dl - α -tocopherol and polyunsaturated lipids was monitored by ESR spectroscopy and chemiluminescence analysis. Suppressing the oxygen supply to the reaction mixture by sealing the sample tube drastically decreased the kinetics of the radical reactions between the antioxidant and the lipid. These radical reactions could in turn be accelerated by reoxygenation of the reaction mixture.

Generation of radicals from antioxidant-type molecules by polyunsaturated lipids

A method for the formation of radicals from antioxidant-type compounds which makes use of the radicals generated during the autoxidation of polyunsaturated lipids is described. This simple system allows observation of radicals by e.s.r. spectroscopy as well as the study of radical exchange reactions in conditions similar to those encountered during lipid autoxidation and biological peroxidation reactions. Advantages and limitations are discussed. Applications presented include studies of the fate of antioxidants and the role of oxygen during lipid autoxidation, investigations of radical exchange reactions occurring in living cells, and of the role of oxidative reactions in the antipsoriatic drug action of anthralin.

Rapid determination of antioxidants with an electrochemical micro flow-through detector Part I: Determination of Tocopherols

ZusammenfassungEine elektrochemische Methode zur Bestimmung von Tocopherolen in Fetten, Ölen und fetthaltigen Lebensmitteln wird vorgeschlagen. Die Besonderheit der vorgestellten Methode liegt darin, daß ein elektrochemischer Detektor benutzt wird, der es erlaubt, mit sehr kleinen Probemengen auszukommen. Überdies hat sich gezeigt, daß die untere Bestimmungsgrenze bei 10−8 mol/1 Tocopherol liegt.SummaryAn electrochemical method for determining tocopherols in oils, fats, and fat-containing foods is presented. The use of an electrochemical detector brings the detection limit down to 10−8 mole/1 tocopherol.

An ESR study of thermal and photo-induced formation of radicals from anthralin and acylated derivatives

Radicals of anthralin and some anthralin derivatives generated either by thermolysis or photolysis in degassed xylene have been monitored by use of ESR spectroscopy. Thermolysis or photolysis of either anthralin or anthralin 10,10′-dehydrodimer generates the 1,8-dihydroxy-9-anthron-10-yl radical. Radical reactions are only observed during thermolysis of C-10 acyl-derivatives or during photolysis of the 1,8-diacyl derivatives. Differences in reactivity of the C-10 methylene group of the various derivatives are discussed.