Study On Secondary Metabolites Of Chaetomium Globosum From Habitat

Natural products were originally generated from medicinal plants and animals,and were an important source for new drugs and new lead compounds.Since endo-symbiotic microorganisms from plants and animals had been found to forming special metabolic pathways which could produce unique compounds structurally with significant biological activities after the long term process of co-evolution with the hosts,and these endo-symbiotic microorganisms could be easily cultured and produced in large scales,endo-symbiotic microbes became the new source for natural active constituents.Chaetomium is one of the large genera of fungi Chaetomiaceae family and contains more than 100 species.Chaetomium genus had been reported as a rich source of various active compounds structurally such as terpenoids,steroids,cytochalasins,xanthones and depsidones.The secondary metabolites from Chaetomium genus were worthy of further research.Chaetomium globosum ML-4 was a symbiotic fungus separated from Oyster(Qingdao marine area,China)by group of Dr.Fengwu Wang,Qingdao Agricultural University and Chaetomium globosum IFB-WQ was an endophyte separated from the medicinal plant Imperata cylindrical by Institute of Functional Biomolecules,Nanjing University.The chemical constituents of the liquid culture of C.globosum ML-4 and the solid culture of C.globosum IFB-WQ were investigated in this dissertation for providing lead compounds for the development of new drugs.The liquid culture of C.globosum ML-4 was extracted with EtOAc to give the crude extract of 3.2g.CH3Cl/MeOH extract of the solid culture of C.globosum IFB-WQ was again extracted with EtOAc and n-butyl alcohol successively to provide the extract of 26 and 17g,respectively.The crude extracts were chromatographed on silica gel column to give several fractions.Guided by TLC and 1H-NMR spectrum,these fractions were then separated and purified using silica gel column chromatography,gel filtration with Sephadex LH-20,reversed phase column chromatography,preparative thin layer chromatography and HPLC.Five compounds(1～5)were obtained from the strain ML-4 and six compounds(1～2 and 6～9)were isolated from the strain IFB-WQ.Structures of the obtained compounds were elucidated by various spectroscopic analysis(MS,1D and 2D NMR)and comparison with references.Compounds 1-9 were identified as iso-chaetoglobosin Vb(1),chaetoglobosin V(2),tyrosol(3),5-methyluracil(4),uracil(5),chaetoglobosin Fex(6),chaetoglobosin W(7),cytoglobosin I(8)and cytoglobosin Ab(9),in which iso-chaetoglobosin Vb(1)and chaetoglobosin V(2)were isolated from both these two strains.NMR data of cytoglobosin Ab(9)was reported for the first time in this dissertation and absolute configuration of iso-chaetoglobosin Vb(1)need to be further determinted.The in vitro cytotoxicity of compounds 1,2,6 and 9 to human hepatocarcinama cell line SMMC-7721 were evaluated by MTT method.Compound 2 showed moderate cytotoxic to SMMC-7721 cells in a dose-dependent manner with an half inhibitory concentration(IC50)value of 60.5μg/mL,while IC50 value of the positive control cisplatin was 7.92μg/mL.Compounds 1,2,6,7,8 and 9 are cytochalasin compounds.This type of compounds had been reported to bear various biological activities such as anticancer,immunosuppression and antioxidant.They were found to possess the neuroprotective activity against MPP+-induced PC 12 cell damage in our previous research,which suggested that they might be the potential natural products for treating the Parkinson’s disease(PD).Aforementioned compounds will be further investigated for their neuroprotective effect for Parkinson’s disease in the future experiment.