Effect of resveratrol and taurine on oxidative hair damage

Hair becomes vulnerable to the effects of oxidative stress due to environmental factors it is exposed to in daily life, especially due to chemical processes such as bleaching, dyeing and perming. This situation disrupts the structural integrity of keratin proteins, disulfide bonds and lipid components in the hair shaft and negatively affects hair health. In this thesis study, it was aimed to evaluate the oxidative damage caused by bleaching process in human hair biochemically and morphologically and to develop a hair care tonic with a protective/repairing effect against this damage. In the first stage of the study, the antioxidant properties of resveratrol and taurine were analyzed by DPPH (1,1-Diphenyl-2- picrylhydrazyl) free radical scavenging method. Resveratrol showed 95±0.6%, taurine 38±2.0%, BHA (butylated hydroxy anisole) 97±0.7% and BHT (butylated hydroxy toluene) 96±0.6% inhibition. IC₅₀ values ​​were calculated as 10.3±0.6 µg/mL for BHT, 6.1±0.4 µg/mL for BHA, 23.5±1.2 µg/mL for resveratrol and >1000 µg/mL for taurine, respectively. Keratin protein was isolated from human hair and 0.265 mg/mL total protein was determined. Binding capacity of resveratrol and taurine with hair keratin was tested by centrifugal sedimentation method, and it was determined that resveratrol and taurine bound with keratin and formed a distinct pellet. When keratin proteins exposed to bleaching solution were analyzed by SDS-PAGE, it was observed that the keratin band completely disappeared in the group exposed only to bleaching solution, while the integrity of the keratin band was preserved in the groups treated with resveratrol and taurine. In the determination of cysteine, it was determined that 100% cysteine ​​release in the damaged hair group decreased by approximately 39.4% with the application of hair care tonic containing resveratrol and taurine. Malondialdehyde (MDA) levels in lipids isolated by lipid extraction were determined spectrophotometrically. While the MDA level was determined as 1.54±0.48 µM/mg in undamaged hair, it was observed that after bleaching this value increased by 1619.1% to 26.51 µM/mg. It was determined that with the application of the tonic before bleaching, the MDA level decreased by 89.93% to 2.67 µM/mg, and with the application after bleaching, it decreased by 97.28% to 0.72 µM/mg. In scanning electron microscope (SEM) imaging; Regular cuticle alignment in untreated hair, severe cuticle damage in bleached hair, and healing and organized structure in damaged areas were observed in the group where the tonic was applied after bleaching. The findings obtained revealed the potential of the developed resveratrol and taurine-based hair care tonic to have both protective and restorative effects. Significant differences were also determined in terms of the order of tonic application, and it was determined that both pre- and post-bleaching applications were effective, but the post-damage application provided a higher rate of repair. It is anticipated that this study may contribute to the scientifically based product development process in hair cosmetics; it is thought that more effective formulations can be developed by integrating biochemical analyses into cosmetic R&D processes.