Recent Advances and Progress on Melanin: From Source to Application

Abstract

Melanin is a biological pigment formed by indoles and phenolic compounds. It is widely found in living organisms and has a variety of unique properties. Due to its diverse characteristics and good biocompatibility, melanin has become the focus in the fields of biomedicine, agriculture, the food industry, etc. However, due to the wide range of melanin sources, complex polymerization properties, and low solubility of specific solvents, the specific macromolecular structure and polymerization mechanism of melanin remain unclear, which significantly limits the further study and application of melanin. Its synthesis and degradation pathways are also controversial. In addition, new properties and applications of melanin are constantly being discovered. In this review, we focus on the recent advances in the research of melanin in all aspects. Firstly, the classification, source, and degradation of melanin are summarized. Secondly, a detailed description of the structure, characterization, and properties of melanin is followed. The novel biological activity of melanin and its application is described at the end.

Bioproduction and optimization of newly characterized melanin pigment from Streptomyces djakartensis NSS-3 with its anticancer, antimicrobial, and radioprotective properties

“…Similar results were reported on the HEP2 carcinoma cell line by Arun, et al [ 120 ], who reported that inhibition of cell viability was concentration-dependent and that 60 µg of melanin inhibited cell viability by 53%. Without harming or adversely affecting other healthy cells or bodily tissues, melanin offers anti-tumor properties that include apoptosis promotion and angiogenesis inhibition [ 126 ]. Melanin has good photothermal conversion efficiency and can absorb light from the ultraviolet to the near-infrared range.…”

Transcriptional convergence after repeated duplication of an amino acid transporter gene leads to the independent emergence of the black husk/pericarp trait in barley and rice

“…Previously, it was thought that plant melanins belong to allomelanin which is devoid of nitrogen (Glagoleva et al ., 2020 ), despite a recent report that all three types (allomelanin, eumelanin and pheomelanin) are present in a medicinal plant Echinacea purpurea (Kurkiewicz et al., 2022 ) and nitrogen‐containing melanins may also be present in barley (Shoeva et al ., 2020 ). Our proposed pathway of melanin formation in barley seem to support the presence of multiple types of melanin as well, which may worth further attention because different types of melanin have been shown to retain varied biochemical properties (Guo et al ., 2023 ).…”

Exploration and analysis of flavonoid melanin inhibitors

“…Among all flavonoids, neorauflavane (18) isolated from Camylotropishirtella is considered to be the most effective inhibitor (the IC50 of monophenolase and disphenolase activity is less than 0.5μm). The inhibitory activity is as high as 400 times that of kojic acid, and only reduces the content of melanin in B16 melanocytes without affecting the cell itself, which indicates that the reduction of geranyl side chain can improve tyrosinase inhibitory activity from the point of view of structure [11].…”