A Melanin-Related Phenolic Polymer with Potent Photoprotective and Antioxidant Activities for Dermo-Cosmetic Applications

Abstract

Eumelanins, the dark variant of skin pigments, are endowed with a remarkable antioxidant activity and well-recognized photoprotective properties that have been ascribed to pigment components derived from the biosynthetic precursor 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Herein, we report the protective effect of a polymer obtained starting from the methyl ester of DHICA (MeDHICA-melanin) against Ultraviolet A (UVA)-induced oxidative stress in immortalized human keratinocytes (HaCaT). MeDHICA-melanin was prepared by aerial oxidation of MeDHICA. At concentrations as low as 10 µg/mL, MeDHICA-melanin prevented reactive oxygen species accumulation and partially reduced glutathione oxidation in UVA-irradiated keratinocytes. Western blot experiments revealed that the polymer is able to induce the translocation of nuclear factor erythroid 2–related factor 2 (Nrf-2) to the nucleus with the activation of the transcription of antioxidant enzymes, such as heme-oxygenase 1. Spectrophotometric and HPLC analysis of cell lysate allowed to conclude that a significant fraction (ca. 7%), consisting mainly of the 4,4′-dimer of MeDHICA (ca. 2 μM), was internalized in the cells. Overall these data point to the potential use of MeDHICA-melanin as an antioxidant for the treatment of skin damage, photoaging and skin cancers.

Natural Phenolic Compounds for Health, Food and Cosmetic Applications

“…The potent photoprotective and antioxidant activities of a DHICA-related phenolic polymer have also been reported by Liberti et al [16]. In particular, the protective effect of a polymer obtained starting from the methyl ester of DHICA (MeDHICA-melanin) against ultraviolet A (UVA)-induced oxidative stress in immortalized human keratinocytes (HaCaTs) was described.…”

Microbial Production of Melanin Pigments from Caffeic Acid and L-Tyrosine Using Streptomyces glaucescens and FCS-ECH-Expressing Escherichia coli

“…Melanin pigment has been shown to have antioxidant properties [ 7 , 28 , 29 , 30 , 31 ]. In particular, eumelanin synthesized through L-tyrosine biotransformation in E. coli has been reported to exhibit antioxidant efficacy at an IC 50 level of 200–300 μg/mL, while homogentisate-based pyomelanin from L-tyrosine had an IC 50 level of approximately 100 μg/mL [ 7 , 17 ].…”

Collagen Extract Derived from Yeonsan Ogye Chicken Increases Bone Microarchitecture by Suppressing the RANKL/OPG Ratio via the JNK Signaling Pathway

“…Yeonsan Ogye is a traditional Korean chicken breed, Gallus gallus domesticus , with the dominant gene responsible for dermal hyperpigmentation (or fibromelanosis) [ 26 ] Abnormal accumulation of eumelanin (photoprotective and antioxidant pigment) in tissues is responsible for the hyperpigmentation of Yeonsan Ogye, causing its unique dark, gray-black coloration, including black fluffy head feathers, earlobes, and pupils [ 27 , 28 ]. This was the first study to simultaneously examine the anti-osteoclastogenic and osteogenic effects of GD collagen (collagen extract obtained from Yeonsan Ogye flesh), via the impairment of the RANKL/OPG ratio, activation of p38 and inhibition of the JNK signaling pathways, in an OVX rat model.…”