Study On The Secondary Metabolites Of Anti-MRSA Activity Of Marine-derived Fungus Aspergillus Sp.L1

MRSA,known as methicillin-resistant Staphylococcus aureus in Chinese,has become one of the most important pathogens of nosocomial infections and a multi-drug-resistant pathogen that seriously threatens human life and health.MRSA infections have appeared all over the world and can be transmitted between animals and humans.MRSE,named methicillin-resistant Staphylococcus aureus in Chinese,is also an important pathogen of nosocomial infection.Because MRSA and MRSE strains have multiple drug resistance,it is difficult to cure them clinically.Therefore,it is urgent to find new compounds with novel structure,significant activity and unique drug resistance mechanism,which have anti-MRSA and MRSE activities.Research on natural products of anti-MRSA and anti-MRSE has also become an important topic.Microorganisms are rich in species and diverse in metabolic pathways.Secondary metabolites have become an important source of precursor drugs.With the deepening of research,the emergence rate of secondary metabolites of terrestrial microorganisms is decreasing and the repetition rate is increasing.People begin to turn their attention to the ocean.Marine microorganisms have become a new and important source of natural products separation.Natural products from a variety of new sources of marine microorganisms have been found.Ten strains of fungi were isolated from the seabed sediments of Daya Bay in China.MRSA and MRSE strains were used as indicators for screening.Finally,a strain with strong activity was found(L1).L1 was identified as Aspergillus sp.The strain L1 was fermented and separated by means of normal phase silica gel column,Sephadex LH20,macroporous adsorption resin and HPLC,with the activity of anti-MRSA and MRSE as the index.Five compounds,H3-1(Xanthocillin X monomethylether.),H3-2(6',8'-dimethoxy xanthocillin X),H3-3(xanthocillin X dimethylether),H4-1 and H3G4-1(xanthocillin analogue BU-4707),were isolated and identified.H3-1,H3-2,H3-3 and H3G4-1 all showed anti-MRSA and anti-MRSE activity.The MIC values were 3.13 ug/ml,25 ug/ml,0.78 ug/ml and 0.39 ug/ml,respectively.H4-1 showed no antimicrobial activity.Compound H4-1 was optimized by single factor,including carbon source,nitrogen source and inorganic salt ion conditions.The optimum carbon source,nitrogen source,inorganic salt ion species and concentration were determined.In this paper,the secondary metabolites of selected marine fungi were studied.Five compounds were isolated and identified.Four of them have anti-MRSA activity,providing strains and compound resources for the development of new drugs.