Ultraviolet Light‐induced Free Radical Formation in Skin: An Electron Paramagnetic Resonance Study

Abstract

It has been suggested that ultraviolet light induces free radical formation in skin, leading to photoaging and cancer. We have demonstrated by electron paramagnetic resonance that the ascorbate free radical is naturally present in unexposed skin at a very low steady state level. When a section of SKH-1 hairless mouse skin in an EPR cavity is exposed to UV light (4,500 J m-2.s-1, Xe lamp, 305 nm cutoff and IR filters), the ascorbate free radical signal intensity increases. These results indicate that UV light increases free radical oxidative stress, consistent with ascorbate's role as the terminal, small-molecule antioxidant. The initial radicals produced by UV light would have very short lifetimes at room temperature; thus, we have applied EPR spin trapping techniques to detect these radicals. Using alpha-[4-pyridyl 1-oxide]-N-tert-butyl nitrone (POBN), we have for the first time spin trapped a UV light-produced carbon-centered free radical from intact skin. The EPR spectra exhibited hyperfine splittings that are characteristic of POBN/alkyl radicals, aN = 15.56 G and aH = 2.70 G, possibly generated from membrane lipids as a result of beta-scission of lipid alkoxyl radicals. Iron can act as a catalyst for free radical oxidative reactions; chronic exposure of skin to UV radiation causes increased iron deposition. Using our spin trapping system, we have shown that topical application of the iron-chelator, Desferal, to a section of skin reduces the UV light-induced POBN adduct radical signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Wrinkle Activity of Ziyuglycoside I Isolated from aSanguisorba officinalisRoot Extract and Its Application as a Cosmeceutical Ingredient

“…21) Assays of the free radical scavenging capacity were carried out by the DPPH method. The free radical scavenging capacity of various native plant extracts was measured at each concentration (1-400 mg/ml), the results being shown in Table 1.…”

Fotoprotetores derivados de produtos naturais: perspectivas de mercado e interações entre o setor produtivo e centros de pesquisa

“…Assim, é a pele quem está constantemente exposta à radiação UV, acreditando-se ser este o maior mediador exógeno de danos. [4][5][6][7][8] Muitos fatores devem ser considerados quando se avaliam os efeitos da radiação UV na pele, tais como o comprimento de onda incidente, a dose e características cutâneas como a susceptibilidade genética individual. 9 Apesar da radiação UVB ser muito mais danosa que a UVA, ao se comparar ambas em iguais condições de exposição, a UVA é mais penetrante e está presente o dia todo, o que leva alguns pesquisadores a sugerir que esta é a responsável pelos maiores danos biológicos.…”

Oxidative balance in macroalgae from Antarctic waters. Possible role of Fe

“…Electron Paramagnetic Resonance (EPR) spectra were measured using a Bruker (Karlsruhe, Germany) spectrometer ECS 106 with a ER 4102ST cavity, operating with the following instrument settings: room temperature (18°C), 9.81 GHz microwave frequency, 22.6 mW microwave power, 50 kHz modulation frequency, 1.232 G modulation amplitude, 81.92 ms time constant and 2 × 10 4 receiver gain (Jurkiewicz and Buettner, 1994). Quantification of the spin adduct was performed using an aqueous solution of 4-hydroxy-2,2,6,6-tetramethyl piperidinyl oxy (TEMPOL) introduced into the same sample cell used for the samples.…”