Synthesis of alpha-tocopheryl oligosaccharides

As effective natural antioxidants, tocopherols and also their esters are frequently added to foodstuffs, pharmaceuticals and cosmetics. For increase of polarity, hence solubility in water, a series of alpha-tocopheryl oligosaccharides was synthesised using BF3-etherate. The pure alpha-tocopheryl beta-maltotetraoside as well as the higher homologues proved to be water-soluble.

Solvent influence on model oxidations of alpha-tocopherol

(+/-)-alpha-Tocopherol has been oxidised with t-butyl hydroperoxide in chloroform in order to simulate in vivo oxidations due to lipid hydroperoxides. t-Butyl hydroperoxide proved to be a weak oxidant and failed to oxidise alpha-tocopherol in 3 h at 60 degrees C. Inclusion of a small amount of ethanol in the reaction mixture brought about immediate oxidation and the formation of a new product, 5-ethoxymethyl-7,8-dimethyltocol in addition to the spiro dimer and spiro trimer of alpha-tocopherol, alpha-tocopherylquinone and 5-formyl-7,8-dimethyltocol. Formation of 5-ethoxymethyl-7,8-dimethyltocol increased with increasing concentrations of ethanol, up to a maximum of 59% at 20% ethanol. Further increase in ethanol concentration brought about a decrease in the oxidation of alpha-tocopherol and in the formation of 5-ethoxymethyl-7,8-dimethyltocol. Oxidation of the tocopherol model compound 2,2,5,7,8-pentamethyl-6-hydroxychroman under similar conditions produced the analogous product, 5-ethoxymethyl-2,2,7,8-tetramethyl-6-hydroxychroman together with 5-formyl-2,2,7,8-tetramethyl-6-hydroxychroman and 2-(3'-hydroxy-3'-methylbutyl)-3,5,6-trimethylbenzo-1,4-quinone.

Vitamin E Oxidation with Alkaline Ferricyanide

Oxidation of dl-alpha-tocopherol or its model, 6-hydroxy-2,2,5,7,8-pentamethylchroman, with alkaline ferricyanide yields a variety of products. In addition to the known dimeric keto ether, two new products, compound A, a trimer, and compound B, an isomer of compound A, were ioslated. Ultraviolet and infrared absorption spectra and paper chromatography indicate that compound A might be identical with liver metabolite "O" which results from the addition of alpha-tocopherol to the diet.