Emulsions Including Cross-Linked Oil Drops and Other Topics

By: Charles Fox, Independent Consultant

Posted: December 23, 2005, from the May 2004 issue of Cosmetics & Toiletries.

Sodium hyaluronate and UV irradiation: Trommer et al have published on the effects of hyaluronan (sodium hyaluronate) and its fragments on lipid models exposed to UV irradiation.  The effects of hyaluronan and its degradation products on irradiation-induced lipid peroxidation were investigated using liposomal skin lipid models with increasing complexity. Hyaluronan and its fragments reduced the amount of lipid peroxidation secondary products quantified by the thiobarbituric acid assay. The changes were studied by mass spectrometry.

To elucidate the nature of free radical involvement, electron spin resonance (ESR) studies were carried out. The influence of hyaluronan and its fragments on the concentration of hydroxyl radicals generated by the Fenton system were examined using the spin trapping technique. Moreover, the mucopolysaccharide’s ability to react with stable radicals was checked. The quantification assay of 2,2-diphenyl-1- picrylhydrazyl hydrate showed no concentration changes of the stable radical caused by hyaluronan.

Hyaluronan was found to exhibit pro-oxidative effects in the Fenton assay in a concentration-dependent manner. A transition metal chelation was proposed as a mechanism of this behavior. Considering human skin and its constant exposure to UV light and oxygen, and an increased pool of iron in irradiated skin, the administration of hyaluronan or its fragments in cosmetic formulations or sunscreens could be helpful for the protection of the human skin.

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