Isolation, characterisation and biological activity of melanin from Exidia nigricans

The aim of present study was isolation and characteriation of raw and purified melanin from Exidia nigricans. Native melanin was isolated from the fresh E. nigricans fruiting bodies by alkaline extraction. Obtained pigment was purifed by acid hydrolysis and washed by organic solvents. Chemical tests, FT-IR and Raman spectroscopy analysis were conducted to determine the melanin nature of the isolated pigment. UV-Vis, transmittance and colour properties were evaluated. Antioxidant activity was determined using ABTS and antibacterial activity by a well diffusion method. The results of the study demonstrated that melanins isolated from E. nigricans had antioxidant, light barrier and antibacterial properties. A purified form of melanin offered better light properties and higher antioxidant activity than the raw form. Both melanins inhibited the growth of E. facealis and P. aeruginosa. This study revealed that E. nigricans may be considered as a promising source of natural melanin. Isolated pigments presented all the physical and chemical properties common to natural and synthetic melanins. Raw and purified melanins showed differences in chemical composition, antioxidant activity and light barrier properties. Melanin may play pivotal role in physiology of E. nigricans protecting it against UV radiation and dessication.