Secondary Metabolites And Their Preliminary Bioactivities From Marine Derived Fungus Aspergillus Ruber

Objective: To study the secondary metabolites and their preliminary bioactivities from marine-derived fungus Aspergillus ruber,to discovery compounds with novel structure and activity.Methods: Firstly,a strain of Aspergillus ruber CTD-5000-2 with antiStaphylococcus aureus activity was screened from the marine fungus library through the antibacterial activity experiment.Secondly,through the "Single Bacteria Multi-Compound Strategy(OSMAC)",the diversity of secondary metabolites of the bacteria was further explored,and the fermentation product of PM-1 medium was determined to have the best antibacterial activity.Subsequently,PM-1 medium was used to expand the fermentation of the bacteria.Guided by antibacterial activity,chromatographic separation technology was used to separate the crude fermentation extract,and the chemical structure of the monomer compound was determined by spectrum technology(NMR,IR,MS,single crystal X-ray diffraction technology).Finally,the microdilution method,DPPH method and MTT method were used to evaluate the anti-Staphylococcus aureus activity,antioxidant activity and cytotoxic activity of the compounds.Results: Thirty compounds(1-30)were isolated and identified from PM-1 fermented extracts with anti-Staphylococcus aureus,of which 3 were new compounds(8,24,25).The compounds : aspergin(1),2-(1,5-heptadienyl)-3,6-dihydroxy-5-(3-methyl-2-butenyl)-benzaldehyde(2),dihydroauroglaucin(3),flavoglaucin(4),isotetrahydroauroglaucin(5),isodihydroauroglaucin(6),auroglaucine(7),rubrumline P(8),tetrahydroechinulin(9),cryptoechinulin G(10),isoechinulin B(11),dehydroechinulin(12),cryptoechinuline D(13),neoechinuline C(14),variecolorin H(15),neoechinulin B(16),isoechinulin A(17),variecolorin J(18),variecolorin G(19),variecolorin I(20),neoechinulin A(21),echinuline(22),variecolorin F(23),(3’S,4’R,5’R,6’R)2-(3-methyl-6-propylcyclohex-4-ene-1,2-dicarboxylic acid)-3,6-dihydroxy-5-(3-methyl-2-butenyl)-benzaldehyde(24),(3’R,4’R,5’R,6’S)2-(3-methyl-6-propylc-yclohex-4-ene-1,2-dicarboxylic acid)-3,6-dihydroxy-5-(3-methyl-2-butenyl)-benzaldehyde(25),preechinulin(26),cryptoechinulin C(27),dihydroxyisoechinulin A(28),rubrumline C(29),variecolorin C(30).Structural categories include 9 compounds of benzaldehyde(1～7,24,25)and21 compounds of indole diketopiperazine(8～23,26～30).Compounds 1,6 and7 had anti-Staphylococcus aureus activity,and the MIC was 8 μg/m L,8 μg/m L,32 μg/m L.Compound 1 was the main anti-Staphylococcus aureus component.Compounds 8～12,14,16,17,19 and 21 had certain activity of scavenging DPPH free radicals,the clearance rate of DPPH was up to 24.2±4.7%,27.1±3.1%,9.6±1.6%,40.7±4.6%,24.6±3.6%,4.5 ± 2.8%,16.9 ± 2.4%,20.0±1.7%,37.5±1.7%,70.6±2.7%.Compounds 5,10,17,22 had cytotoxic activity.Conclusion: Three compounds with novel structures have been discovered from the marine fungus Aspergillus ruber CTD-5000-2,which enriches the structural diversity of secondary metabolites from this genus of fungi and marine sources.Some compounds from Aspergillus ruber CTD-5000-2 had antioxidant activity,antimicrobial activity and cytotoxic activity.