Structure,Biological Activity And Mechanism Of Lachnum Sp.Melanin And Derivative

In the present study,an intracellular melanin(LIM)of Lachnum YM30 was obtained by submerged fermentation,extraction and purification.The possible structural formula of LIM was concluded base on UV,FTIR,elemental assay,NMR and MS spectrometry.The experimental results showed that LIM had the typical features of fungal eumelanin.The study aimed to investigate the antibacterial activity of LIM.The dilution method was used to measure the MIC and MBC of Gram-negative bacteria Escherichia coli,Salmonella typhi,Vibrio parahaemolyticus and Gram-positive bacteria Listeria monocytogenes,Bacillus megaterium,Staphylococcus aureus.Bacteriostasis of LIM against S.aureus and V.parahaemolyticus was further revealed by SEM observation,testing permeability of cell membrane,NPN uptake and membrane potential.MTT experiment was used to estimate the cell cytotoxicity of LIM.The results showed that LIM significantly changed the permeability of cell membrane,increased the leakage of cell contents,raised the quantity of NPN uptake and reduced the membrane potential.LIM had no obvious cell cytotoxicity at low concentrations.These findings indicated that LIM had antibacterial activity and could be applied as a potential natural bacteriostatic agent in the food or pharmaceutical industry.Arginine-melanin(ALIM)was prepared and the structure was studied by FTIR and MS.The hepatoprotective effects of LIM,ALIM and positive drug+LIM were evaluated in an acute LPS/D-GalN induced liver injury mice model.The serum levels of alanine aminotransferase(ALT)and aspartate transaminase(AST)in the pretreatment groups were significantly lower than the model group.Pretreatments with LIM and ALIM can effectively reduce the levels of nuclear transcription factor kappa B(NF-?B),serum interleukin-1?(IL-1?),tumor necrosis factor alpha(TNF-?),cytokines,interleukin-8(IL-8),inducible nitric oxide synthase(i NOS)and NO,increase the hepatic levels of interleukin-4(IL-4)and interleukin-10(IL-10).The experimental results show that LIM and ALIM can protect liver against LPS/D-GalN toxicity via reducing inflammatory stress.The results showed that the LIM and ALIM could protect the liver and combined treatment group could further reduce the inflammatory effect of the model drug on the mice compared with the single positive drug treatment or the melanin treatment groups.These results suggest that LIM and ALIM are potential prophylactic agents that can be used to prevent LPS/GalN-induced liver injury and that combination therapy is also a potential treatment for reducing liver injury in the model.