UV damage to hair and the effect of antioxidants and metal chelators

Abstract

Objective To study the effects of addition of a redox metal, copper, antioxidants and metal chelators on the formation of free radicals in natural white Caucasian hair subsequently exposed to UV light. Three different methods, electron paramagnetic resonance (EPR), a fluorescent probe for hydroxyl radical formation (terephthalate) and free radical photoyellowing, were used. These methods utilized different UV sources and reaction conditions, and so can give insights into the different mechanisms of action occurring during UV oxidation of hair. In addition, this study demonstrates how antioxidants and chelators can be screened to determine whether they can protect hair from UV damage. Results The three methods gave somewhat different results, illustrating the importance of reaction conditions and wavelength on the photochemical mechanisms, and the efficacy of additives to influence these reactions. EPR results showed that N‐acetylcysteine (NAC) pre‐treatment eliminated the intensity of the signal because of sulphur and carbon free radicals in white hair both before and after exposure to UVB radiation. Doping the hair with copper ions had no effect on the intensity of the EPR signal under dry conditions. Terephthalate fluorescent probe data showed that under wet conditions, irradiation of white hair with UVA produced significant amounts of hydroxyl radicals. Pre‐treatment of hair with NAC reduced the number of •OH radicals produced by natural white hair compared to an untreated control. In contrast to the EPR result, white hair doped with copper ions produced significantly higher levels of •OH radicals under wet conditions. It appears that the ability of copper ions to catalyse the photogeneration free radicals in hair is highly dependent on water content. Photoyellowing data showed a benefit for oxalic acid but no difference for NAC and an increase in yellowing for EDTA. Conclusion The micro‐EPR and terephthalate fluorescent probe methods are both effective techniques to study production of free radicals by hair exposed to UV light under wet and dry conditions, respectively. Both assays are simple methods for determining the effectiveness of potential protective hair treatments against UV damage, but because they assess free radical damage under dry vs wet conditions, the chemistry created on UV exposure is different. This gives insights into mechanism of action, but results may not be consistent between the two methods for actives added for reduction of UV damage. NAC pre‐treatment did reduce free radical generation in UV‐exposed hair under both wet and dry conditions. Photoyellowing data are more complicated as it is a less direct measure of UV damage and is highly dependent on irradiation source. Using UVB irradiation is experimentally convenient but may not be appropriate, because UVB wavelengths comprise only 0.3% of terrestrial sunlight. The photochemistry of hair exposed to sunlight involves concurrent photobleaching and photoyellowing processes and is far more complex. Under UVB irradiation condit...

Assessment of the photoprotection properties of hair cosmetics using the hemispherical directional reflectance method

“…It seems important to establish appropriate conditions, similar to those during the sun exposure. These are irradiation time, humidity, temperature, and radiation intensity 2,3,12 …”

“…These are irradiation time, humidity, temperature, and radiation intensity. 2,3,12 TA B L E 5 Reflectance of light hair at seven wavelength ranges, before the application of protective products (t0) and immediately after its application (t1), 20 min after (t2), 1 h after (t3), 1.5 h after (t4), and 2 h after (t5) application; Med-median, Q1-first quartile, Q3-third quartile, Min-minimum, Max-maximum, p-level of significance, ns-not significant. The results obtained using the 410-Solar reflectometer allow to determine the effectiveness of the hair filters in vivo.…”

“…The presence of copper ions in the hair, caused by the use of tap water, also contributes to the increased hydroxyl radicals formation in a humid environment. 12 So far, the directional reflectance method has not been used to test the effectiveness of hair sunscreens in any research project before.…”

A review of developments in industrial hair colorant actives for oxidative dyes

“…While the necessity of combatting the latter's ability to destabilise oxidant solutions prior to use has long been known, 16 the presence of redox‐active metals within the hair shaft is believed to contribute to catalytic decomposition of peroxide into species, which, fortunately, accelerate the coloration process relative to reaction in aqueous solution outside of the hair fibre 10 . A downside to the presence of such metals, in particular that of copper, is the adverse effect of catalysing the formation of destructive radicals which damage hair 190,191 . EDDS suppresses their formation and resultant cuticle damage during coloration more effectively than the traditional chelant EDTA.…”

Community Service: Safe, Effective, and Beneficial Skincare Counseling for Kalam Kudus II Jakarta High School Students

“…To avoid this, the skin must be shielded from these negative impacts. (Bucci et al, 2018;Mao et al, 2020;Millington & Marsh, 2020;Wang et al, 2014) Teenagers are required to use cosmetics or beauty products to enhance their appearance.…”