engleski

(Anti)oxidative properties of vitamin C topical formulations

Purpose of the work: Ascorbic acid or vitamin C is generally well known as an antioxidant but some studies have shown that it could also act as a pro-oxidant. The valuable effects of ascorbic acid against skin hyperpigmentation and aging are usually related to its antioxidant properties. As topical formulations with ascorbic acid (especially serums) are popularly used among women of different ages, the aim of the study was to compare three commercially available skin serums with a differently declared concentrations of ascorbic acid, using different in vitro and ex-vivo models. Materials and methods: Spectrophotometric (Trolox equivalent antioxidant capacity (TEAC)) and spectrofluorometric (Oxygen radical absorbance capacity (ORAC)) methods were used to determine total antioxidant capacity (AOX) of serum A, serum B and serum C, used in this study. In order to investigate potentially protective effect of tested serums on lipid peroxidation, all three serums, applied with linoleic acid (LA), were exposed to ultraviolet (UV) radiation, as a model of oxidative stress. Lipid peroxides were measured by thiobarbituric acid (TBA) assay and quantified by spectrophotometry. Furthermore, the serum that expressed the best results in vitro, was tested in vivo as well. Serum was topically applied on the left volunteers’ forearm (3 mg/cm) while the other forearm was the control. Two test sites on each forearm were stripped 1 hour after application, using sampling discs. Half of the strips were exposed to UV radiation (214, 2 J/cm2), and the other half were not- irradiated. Discs' content of lipid peroxides (malondialdehyde, MDA) were measured with TBA assay using spectrofluorometry. Results: AOX levels of serum A, B and C were different and not in correlation with their declared concentration of ascorbic acid. Measured by TEAC method, AOX levels were 858.3, 113.5, 16.3 µmol/L Trolox equivalents, and measured by ORAC method, AOX levels were 463.7, 243.0, 86.7 µmol/L Trolox equivalents for serum A, B and C, respectively. Interestingly, two vitamin C serums induced an increase of lipid peroxides when applied with LA and exposed to UV, when compared to control (2.8 and 2.3 times higher levels of MDA than the values of control for serum A and B, respectively). The most potent serum (A) was tested in ex-vivo experiment, where it showed pro-oxidative effects as well, in comparison to control. Conclusions: Further studies, with different experimental models, are warranted to explain this dualistic (anti)oxidative properties of vitamin C when applied topically.

vitamin C, antioksidativna svojstva, topikalna formulacija

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