Isolation, characterization and assessment of the photoprotective effect of two fungal melanins

• Main Author: Olaizola, Carolina
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/43603

Melanins are a diverse group of pigmented biopolymers present in living organisms at all phylogenetic levels. Properties such as light scattering and absorption through a wide range of wavelengths, and scavenging of free radicals are common to all melanins, and render them as molecules having the capacity to protect against UV damage. Fungal melanins are more chemically diverse than animal melanin, and have radioprotective properties. In this research, I isolated melanins from the basidiomycete Agaricus bisporus and the ascomycete Grosmannia clavigera, and assessed their photoprotective effect in human skin cells. Both fungal melanins differed in physicochemical characteristics and functional groups evidenced by infrared spectral analyses. Differences in the evaluated bioactivity were also observed. Agaricus bisporus melanin behaved similar to synthetic DOPA melanin, significantly enhancing cell viability measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in human dermal fibroblasts irradiated with a high dose of ultraviolet B (UVB). Agaricus bisporus melanin also effectively reduced the amount of reactive oxygen species (ROS) induced by UVB in these cells. Measurements of light transmission at 315 nm of melanin solutions suggest that the observed photoprotective effect was likely to be due to a UV filter effect. No photoprotection was observed in cells exposed to UVB in the presence of Grosmannia clavigera melanin. Unlike synthetic DOPA melanin, both fungal melanins were potentially cytotoxic for human dermal fibroblasts. My results suggest that differences observed in the fungal melanin bioactivity are possibly linked to differences in their chemistry and optical properties.