Secondary Metabolites And Antibacterial Activities Of Two Endophytic Fungi From Sophora Tonkinensis

Endophytic fungi,as sources of bioactive products,can produce numerous and bioactive compounds through their unique metabolism way,which make the endophytic fungi become a hotspot of the research in recent years.Sophora tonkinensis,belongs to genus Sophora Subprostrata,is distributed chiefly in South China.As an important traditional Chinese medicinal plant,it roots are commonly used to treat acute pharyngolaryngeal infections and sore throats.In this paper,two endophytic fungi GDG-102 and GDG-178 isolated from S.tonkinensis have been researched.In order to obtain antibacterial compounds,the metabolites of the fungi are isolated under the guidance of antibacterial activity.The results provide an important scientific reference for finding naturally antibacterial products from endophytic fungi.This paper mainly includes the folowing five parts:The first part introduced the recent research progress on secondary metabolites of endophytic fungi Xylaria sp.and Fusarium sp..The second part introduced the separation of endophytic fungi and determination of antibacterial activities.153 strains of endophytic fungi are isolated from the roots,stems and leaves of Sophora tonkinensis by tissue section method.Screening 51 strains endophytic fungi and testing their antibacterial activities.The results showed that endophytic fungi of S.tonkinensis contains a large number of antibacterial components.The third part introduced isolation and structure identification of secondary metabolites of GDG-102.By cultivated stationary and ten compounds are isolated from the secondary metabolites of endophytic fungi GDG-102 through repeated column chromatography(CC)on silica gel,reverse phase silica gel column chromatography,Sephadex LH-20,recrystallization,as well as semi-preparative HPLC.All of them identified by spectral data analyses,such as MS,NMR and single crystal X-ray diffraction analysis.These compounds were elucidated as xylarphthalide A(102-1),(-)-5-carboxylmellein(102-2),(-)-5-methylmellein(102-3),cytochalasin K(102-4),cytochalasin E(102-5),6-hepanoyl-4-methoxy-2H-pyran-2-one(102-6),dihydrosporothriolide(102-7),2-butyl-3-methylsuccinic acid(102-8),(22E)-Ergosta-7,22-diene-3β,5α,6β-triol(102-9)and ergosterol peroxide(102-10),respectively.102-1 and 102-6 were new compounds by the SCIFINDER searching.The absolute configurations of 102-1 was confirmed by single crystal X-ray diffraction analysis.The fourth part introduced isolation and structure identification of secondary metabolites of GDG-178.By cultured stationary and eleven compounds are isolated from the secondary metabolites of endophytic fungi GDG-178 through chromatography methods.All of them identified by spectral data analyses,such as MS,NMR.These compounds were elucidated as sterigmatocysin(178-1),ergosterol(178-2),oxisterigmatocystin D(178-3),5-methoxydihydrosterigmatocysin(178-4),aversin(178-5),averythrin(178-6),6,8-di-O-methyl averufin(178-7),5-methoxysterigmatocysin(178-8),6,8-di-O-methylnirufin(178-9),emodin(178-10)and versicamides A(178-11)by using spectroscopic methods.Compounds 178-1,178-3,178-4,178-5,178-6,178-7,178-8,178-9 and 178-11 are isolated from F.equiseti for the first time.The fifth part mainly introduced determination antibacterial activities of the compounds by double broth dilution method.Through double broth dilution method to test the antibacterial activities of the compounds isolated from GDG-102 and GDG-178.The results showed that most of the compounds have a good antibacterial activity.During the metabolites of endophytic fungi GDG-102,isocoumarin compounds 102-1,102-2 and 102-3 exhibited a good antibacterial activity against B.subtilis,S.aureus,S.dysenteriae and E.coli,with MIC values from 12.5μg/mL to 25μg/mL.Cytochalasin compounds 102-4 and 102-5 also showed antibacterial activities on S.aureus,B.anthracis,S.dysenteriae and E.coli,with MIC values from 12.5μg/mL to 25 μg/mL.During the metabolites of endophytic fungi GDG-178,the antibacterial activities of compounds 178-1,178-3,178-5,178-6,178-7,178-8 and 178-11 to B.subtilis,178-3,178-4,178-6,178-8 and 178-11 to B.megaterium,178-6 to S.dysenteriae were strong(MIC=6.25 μg/mL).178-1 and 178-6 showed a strong antibacterial activity to E.coli,with MIC value 3.125 μg/mL,which was equal to the positive control drug.