The Study Of Secondary Metabolite From Marine Fungus Aspergillus Ruber And Its Biological Activity

The ocean is the source of life for all things on the planet.In the ocean,more than 80%of the biological resources on the planet exist.Marine microbial secondary metabolites have complex and diverse structures and unique activities,and have become an important source for marine drug development in search of lead compounds.Marine fungi,as the main component of marine microorganisms,have become the focus of scholars at home and abroad in recent years.Scholars at home and abroad have isolated a large number of active substances from the secondary metabolites of marine fungi.The research object of this paper is a strain of fungus WH4-1 isolated from the sediments in the offshore waters of Weihai,Shandong.The strain was identified as Aspergillus ruber based on comprehensive ecological colony characteristics,microscopic observation and genetic identification.The experimental strains were subjected to large-scale fermentation and organic solvent extraction of fermentation products,and then Aspergillus ruber crude extract was separated and purified by various chromatography techniques,and a series of monomer compounds were separated and identifiedA total of 23 compounds were isolated from Aspergillus ruber fermentation products by comprehensive use of thin-layer chromatography,normal(reverse)phase silica gel chromatography,and high-performance liquid chromatography.1H NMR,13C NMR,APT,1H-1H COSY,HMQC,HMBC,NOESY,UV,and infrared identification methods were used to identify the structure and three new alkaloids were found:(-)-(S)-variecolortide D(1a*)?(+)-(R)-variecolortide D(1b*)?Brevicompanine I(4*);thirteen known indol alkaloids:Variecolortide B(2),Uncarilins B(3),Preechinulin(5),Tardioxopiperazine B(6),Tardioxopiperazine A(7),Echinuline(8),Neoechinulin A(9),Isoechinulin A(10),Variecolorin G(11),Variecolorin A(12),Dihydroxyisoechinulin(13),Variecolorin C(14),Variecolorin E(15),Neoechinulin E(16);seven anthraquinone derivatives:1,3,8,10-tetrahydroxy-6-methyl-9(10H)-anthracenon(17),Catenarin(18),Questin(19),Rubrocristin(20),2-methyl-Eurotinone(21),Variecolorquinone B(22),Aspergentisyl A(23).Among them,the new compound Variecolortide D(1)is a racemic natural product composed of anthraquinone and isoechinulin type alkaloids,which was purified by chiral HPLC to obtain la and 1b as optically pure enantiomers.Anti-inflammatory biological activity test(NO detection of macrophages)was performed on some of the compounds that had been isolated and identified.The results showed that compounds 2,21,22 had moderate inhibition of NO production in RAW 264.7 cells by lipopolysaccharide(LPS)stimulation Activity,the inhibition rate was 53.2%,63.5%and 50.1%at 30?M,respectively.Compounds 10,4,19,and 20 had weaker inhibitory activities,and the inhibition rates at 30?M were 26.97%,26.25%,35.63%,and 24.31%,respectively.In addition,the antibacterial activity of all compounds against seven pathogenic bacteria was also evaluated.The research results show that compounds 1 and 2 have weak antibacterial activity against the pathogenic bacteria S.aureus ATCC29213,with MIC values of 25 ug/mL.1 and 21 have moderate inhibitory activity on the pathogenic bacteria E.faecalis ATCC51299,and the MIC values are all 12.5 ?g/mL.This study enriched the chemical study of the marine fungus Aspergillus ruber,enriched the structure of the diketopiperazine indole alkaloid,and obtained lead compounds with anti-inflammatory and antibacterial activity from it,providing a basis for its further development.The development of marine drugs has important value.