Secondary Metabolites Of Symbiotic Fungus Aspergillus Sp. Bdf-2 And Their Biological Activities

There are many kinds of insects,and there are also a variety of symbiosis microorganisms with insects.Insect symbiotic fungi are important sources of active secondary metabolites.Based on our previous studies,symbiotic fungus Aspergillus sp.Bdf-2 of Blaptica dubia was used as the research object.Through large-scale fermentation the secondary metabolites were extracted and prepared,and further purified and identified and determined their biological activities.The main results are as follows:(1)A total of 20.7 g of petroleum ether and 113.5 g of ethyl acetate secondary metabolites were prepared by rice solid medium fermentation.Ten compounds were obtained from the petroleum ether and ethyl acetate layer by means of reduced pressure silica gel column chromatography,sephadex LH-20 assay,recrystallization purification,and semi-preparative HPLC,wherein Bdf2-B,Bdf2-D and Bdf2-E were isolated from the petroleum ether layer,Bdf2-A,Bdf2-C,Bdf2-G,Bdf2-H,Bdf2-I,Bdf2-J and Bdf2-L were isolated from the ethyl acetate layer.(2)Multiple spectroscopy methods such as ¹H NMR,¹³C NMR,COSY,HMBC,HSQC,NOESY and HR-ESI-MS were used and relevant literatures were consulted.10compounds were finally identified as Terphenyllin(Bdf2-A),4,4''-Deoxyterphenyllin(Bdf2-B),4"-deoxyterphenyllin(Bdf2-C),Dechlorflavonin(Bdf2-D),3''-hydroxyterphenyllin(Bdf2-G),Fellutanines A(Bdf2-H),3,3''-dihydroxyterphenillin(Bdf2-I),Protocatechuic acid(Bdf2-K)and Candidusins A(Bdf2-L).Bdf2-E was a new compound,named 4''-Deoxy-2'-methoxyterphenyllin.Among these 10 compounds,there were seven p-terphenyl derivatives(Bdf2-A,Bdf2-B,Bdf2-C,Bdf2-E,Bdf2-G,Bdf2-I and Bdf2-L),one flavonoid compound(Bdf2-D),one alkaloid compound(Bdf2-H)and one phenolic acid compound(Bdf2-K).(3)3,3''-dihydroxyterphenillin(Bdf2-I)showed the best antibacterial activity,and the minimum inhibitory concentration(MIC)against Staphyloccocus aureus(G⁺)and Ralstonia solanacearum(G^-)were all 32?g/m L.The MIC values of amikacin for both bacteria were all 1?g/m L.The IC₅₀ value of Terphenyllin(Bdf2-A)against Colletotrichum gloeosporioides was 1.12 mg/m L.3,3''-dihydroxyterphenillin(Bdf2-I)showed the best antioxidant activity,the scavenging capacity of DPPH IC₅₀ was 16.60?g/m L.The IC₅₀value of BHT was 43.44?g/m L.The IC₅₀ value of Terphenyllin(Bdf2-A)for Hep G2 was12.11?g/m L,and the IC₅₀ value for Hela was 23.48?g/m L,The IC₅₀ value of positive control Camptothecin against Hep G2 was 3.6?g/m L,and Hela was 6.3?g/m L.This study provides a basis for the development and utilization of bioactive substances in the symbiotic fungus Aspergillus sp.Bdf-2,the creation of new drugs and the revealing of the physiological and ecological functions of symbiotic fungus.