Synthesis and application of a novel sunscreen-antioxidant

Abstract

Background information on the inefficacy of sunscreens to provide free radical protection in skin, despite their usefulness in preventing sunburn/erythema, prompted us to synthesize a compound which would display in the same molecule both UV-absorbing and antioxidant capacities. For this purpose, the UVB absorber, 2-ethylhexyl-4-methoxycinnamate (OMC) was combined with the piperidine nitroxide TEMPOL, which has antioxidant properties. The spectral properties of the new nitroxide-based sunscreen (MC-NO) as well as its efficacy to prevent photo-oxidative damage to lipids induced by UVA, natural sunlight and 4-tert-butyl-4-methoxydibenzoylmethane (BMDBM), a photo-unstable sunscreen which generates free radicals upon UV radiation, was studied. The results obtained demonstrate that MC-NO: (a) absorbs in the UVB region even after UVA irradiation; (b) acts as free radical scavenger as demonstrated by EPR experiments; (c) strongly reduces both UVA-, sunlight- and BMDBM-induced lipid peroxidation in liposomes, measured as reduced TBARS levels; and (d) has comparable antioxidant activity to that of commonly used vitamin E and BHT in skin care formulations. These results suggest that the use of the novel sunscreen-antioxidant or of other nitroxide-based sunscreens in formulations aimed at reducing photoinduced skin damage may be envisaged.

Radical scavengers: A practical solution to the reproducibility issue in the fluoridation of diaryliodonium salts

“…2) were selected based on their previously demonstrated ability in this role. These included 4-aminobenzoic acid [27], 2,6-di-tert-butyl-4-methylphenol (BHT) [28,29], 1,1-diphenylethylene [30], galvinoxyl [31][32][33], gentisic acid [ [34][35][36], hydroquinone [37][38][39], TEMPO [33,40], thiophenol [41], and DL-a-tocopherol [29].…”

Chemistry and Antihypertensive Effects of Tempol and Other Nitroxides

“…Tempol interacted with other antioxidants to promote their ability to reduce oxidized lipids (Champion et al, 2004). Nitroxides prevented oxidative damage in many cellular or organ systems, for example, in the skin after UV radiation (Damiani et al, 2006; Shen et al, 2006), in cells after x-irradiation (Hahn et al, 1992b, 2000; Sasaki et al, 1998), or in tissues after incubation in a high glucose-containing medium (Xia et al, 2006). …”

Nitroxides and a nitroxide-based UV filter have the potential to photoprotect UVA-irradiated human skin fibroblasts against oxidative damage

“…These compounds display in the same molecule both UV-absorbing and antioxidant properties and could find applications for reducing skin photo-oxidative damage. In fact, preliminary results indicate that these compounds are photostable, act as free-radical scavengers, reduce UVA-and sunlight-induced lipid peroxidation in liposomes and human skin fibroblasts, are non-cytotoxic to these cells and have comparable antioxidant activity to that of vitamin E commonly used in skin care formulations [19,20]. To explore further the photoprotective potential applications of these versatile molecules, we here studied the effects of a nitroxide-based UV filter together with both aromatic and aliphatic nitroxides, on cultured human skin fibroblasts exposed to UVA radiation.…”