ESR study of photoinduced free radicals by visible light in hair and the effects of ascorbic acid (vitamin C)

Abstract

The ESR spectra of melanin's free radicals in natural black and red hair have been investigated. It is shown that the ESR spectrum of black hair is slightly asymmetric singlet with g=2.0037 and ΔH=0.5 mTl. The ESR spectrum of red hair with g=2.0053 differs from the spectrum of black hair. Using the method of saturation was shown that ESR spectrum of red hair represents a superposition of two signals: a singlet, relating to the black hair, and a triplet from red hair's pheomelanin. Under the influence of visible light (blue with λ(max) =450 nm, green with λ(max) =510 nm and red with λ(max) =650 nm) in both types of hair (black and red), the photoinduced free radicals appear, which indicates an increase in the intensity of already existing ESR spectrum of hair. It should be noted that the ESR spectra of red hair from various donors are different. The antioxidant ascorbic acid (vitamin C) has the different effect on the photoinduced free radicals. In particular, in the case of black hair, the concentration of photoinduced free radicals is slightly reduced, whereas in red hair, the disappearance of the triplet in the spectrum is observed, and at the same time, the spectrum becomes a singlet, the intensity of which increases sharply. It is assumed that the antioxidants, effective for black hair, may be ineffective for red hair and vice versa. Therefore, in each, specific case is necessary to investigate the effectiveness of an antioxidant separately.

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

“…It has to be noted that the g‐factor of each separate free radical is a constant parameter, but the g exp ‐factor, measured by the authors, defines the maximum position of the total ESR signal (Fig. ) and is dependent on the concentration ratio of eumelanin (eu) and pheomelanin (pheo) in the total spectrum …”

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

“…In the same research we have also shown that ESR spectrum of the red hair is superposition of two ESR spectra-singlet of eumelanin and triplet of pheomelanin. According to ESR spectra observed in the study, it turned out that red hair of different donors contains different concentration of pheomelanin, [9] and that there are two different types of ESR spectra observed in human red hair: usually observed type I and rarely observed type II (Fig. 2).…”

“…[5][6][7] It was found out, that not only the UV irradiation, but also the visible light and IR can initiate generation of free radicals in the skin and hair. [8][9][10][11] Pheomelanin and its biological role in the human body have not been studied thoroughly yet. However, we know that this pigment has properties of prooxidant, which means that it is capable of generating harmful free radicals in the skin.…”

Characterization of Melanin Radicals in Paraffin-embedded Malignant Melanoma and Nevus Pigmentosus Using X-band EPR and EPR Imaging

“…3) and the spectral pattern was similar to that of previously reported pheomelanin-related radicals. 8,17 The low and high field signal intensities were markedly deferent (asymmetric pattern), suggesting that the radicals were immobilized. 8 The low and high field peak distance was approximately 3.2 mT.…”

“…The characterization of pheomelaninrelated radicals is important as pheomelanin breaks down under light irradiation with the formation of superoxide. 17 Two-dimensional (2D) EPR image of MM and NP with DPPH (upper-panel) and without DPPH as a known radical concentration (lower-panel) is presented in Fig. 4a.…”