MIXTURES OF STEAROYL-6-O-ASCORBIC ACID AND ALPHA-TOCOPHEROL - A MONOLAYER STUDY AT THE GAS WATER INTERFACE/

In the recent past the antioxidant properties of vitamin C, vitamin E, and their derivatives have been extensively studied, particularly for their peculiar activity as radical scavengers. Furthermore, the assoc iation of vitamin C with vitamin E shows an interesting synergic effec t in preventing the oxidation of unsaturated fatty compounds such as l inoleic acid, with vitamin C acting as a protective shield for vitamin E in solution against oxidizing agents. Vitamin C derivatives, such a s its alkanoyl-6-O-ascorbic acid esters, act even better than ascorbic acid itself, because they possess the amphiphilic structure that allo ws the molecule to enter the hydrophobic region of a micelle or of a l iposome. In order to deepen the understanding of the vitamin C/vitamin E mixed system and of the role played by ascorbic acid in restoring t ocopherols, the miscibility properties of ascorbic acid derivatives an d of tocopherols need to be studied in all states of aggregation (Lang muir monolayers, micellar dispersions, vesicles). In this paper we rep ort a detailed study of the properties and behavior of monomolecular f ilms of stearoyl-6-O-ascorbic acid (ascorbyl stearate), and alpha-(+/- )-tocopherol at different temperatures and pH, and of their mixtures a t 20 degrees C at the gas/water interface. Our results show that ascor byl stearate produces monolayers with both liquid-expanded and liquid- condensed phases, while alpha-tocopherol films are in the liquid-expan ded phase only. The two pure components are completely miscible at the gas/water interface in all ratios, and indicate the presence of repul sive interactions between the hydrocarbon chains of the surfactants.