Electron spin resonance (ESR/EPR) of free radicals observed in human red hair: a new, simple empirical method of determination of pheomelanin/eumelanin ratio in hair

Abstract

The definition of the concentration of pheomelanin in the skin is an issue of great interest because in the case of being influenced by UV radiation, it manifests itself as a prooxidant, causing various skin disorders including melanoma that might help to explain the relatively high incidence of skin cancer among individuals with red hair. The ESR spectra of red hair samples were investigated. It was found that at low microwave power, they are characterized by two types of spectra. Red hair ESR signals result from a superposition of two spectral shapes, a singlet spectrum as a result of the existence of eumelanin and a triplet spectrum as a result of the existence of pheomelanin. At high microwave power, only triplet spectra shape was detected, caused by saturation of the eumelanin singlet. Using different concentration ratios of black to red hair, we measured ESR spectra and plotted the ratio values in each sample against a measured 'g-factor' (experimental). We found that there is a linear relationship between these two parameters. So, it is evident that using these results, the concentration ratio of pheomelanin to eumelanin in a sample of hair can be easily determined by an almost noninvasive method. This can be considered a potential advantage for many practical activities compared with other invasive methods. The concentration dependence curve of pheomelanin (µg/mg) on gexp-factor in an ESR spectrum of hair has been designed, which allows the determination of the amount of pheomelanin in hair of any color.

Effect of ascorbic acid (vitamin C) on the ESR spectra of the red and black hair: pheomelanin free radicals are not always present in red hair

“…2). [40] The aim of this study was to define optimal dose of effective concentration of ascorbic acid, capable of neutralizing free radicals of pheomelanin. In addition, we investigated dynamics of changes of free radicals.…”

“…(Conditions of recording the spectra see [40] .) Hair samples were immersed in an ascorbic acid water solution with different concentrations of ascorbic acid and for different periods of time and were dried at dark place during 12 h at room temperature.…”

Honey, a Gift from Nature to Health and Beauty: A Review

“…The core of the hair fibre which is located immediately below the cortex is the medulla. This layer is unique as it is only present in thick dark hair and not in grey aging hair (Chikvaidze et al 2014). …”

Application of Electron Paramagnetic Resonance Spectroscopy to Examine Free Radicals in Melanin Polymers and the Human Melanoma Malignum Cells

“…This absorption is the base of electron paramagnetic resonance (EPR) spectroscopy [41][42][43]. Free radicals in eumelanin [17-19, 26, 40] and pheomelanin [22,31,[38][39][40] are responsible for the EPR spectra, which difer in the shape. Typical EPR spectra of the model eumelanin DOPA-melanin and pheomelanin are shown in Figure 2.…”

“…Comparison of the lineshape of these EPR spectra indicates that eumelanin reveals the simple single line (Figure 2a) and EPR line of pheomelanin reveals the complex shape with the unresolved hyperine structure (Figure 2b). The lineshapes of the EPR spectra of DOPAmelanin [17-19, 26, 34-37] and pheomelanin [22,31,[38][39][40] were presented in a lot of papers. EPR spectra were measured for free radicals in melanotic tumor cells [44][45][46][47][48][49][50][51][52].…”