Purification, structure and anti-radiation activity of melanin from Lachnum YM404

Extracellular melanins (LEM404) were extracted from Lachnum YM404 with a yield of 3.45 g/L. LEM404-a, LEM404-b, LEM404-c, LEM404-d and LEM404-e were fractionated from LEM404 by Sephadex G-15 column. LE404-a was detected as the homogeneous component with molecular weight of about 432.18 Da. Based on the elemental analysis, mass spectrometry, infrared spectroscopy, pyrolysis–GC–MS and NMR analysis, the molecular formula (C22H12N2O4S2) and structural formula of LEM404-a were concluded. LEM404-a could significantly increase the survival rates of Escherichia coli, Staphylococcus aureus and Saccharomyces cerevisiae under UV radiation. Anti-radiation experiments in mice showed that the skin manifestations in mice of low radiation dose experimental group (LEG) were similar to those in blank control group (BCG). Compared with the control groups (LCG and HCG), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in mice of experiment groups (LEG and HEG) were improved significantly while malondialdehyde (MDA) content were decreased significantly, indicating that LEM404-a had strong anti-ultraviolet radiation activity.