Studies On The Antifungal Constituents Of Lysobacter Enzymogenes C3

A wide variety of microorganisms exist in nature, which can produce numerous secondry metabolites with various skeletons and bioactivities. Therefore, microorganism have been a very important source for searching new bioactive natural products.In this dissertation, in order to search for new antifungal compounds, I carried out the isolation of secondary metabolites from the strain Lysobacter enzymogenes C3, and its OX4deletion mutant, together with four strains of plant endophytes.L. enzymogenes C3was effective in inhibiting multiple crop fungal pathogens, was and is used in biological control widely. Polycyclic tetramate macrolactams (PTMs) are the major secondary metabolites of the L. enzymogenes C3. PTMs have been isolated from various microorganisms. This type of compounds belong to hybrid polyketide-nonribosomal peptide antibiotics, and share a macrocyclic lactam ring with an tetramic acid ring along with a variable carbocyclic rings. HSAF (Heat-Stable Antifungal Factor) is a PTM isolated from the strain L. enzymogenes C3, and showed an unprecedented mode of action for an antifungal metabolite by disrupting sphingolipids important to the polarized growth of filamentous fungi. Thus, the study of HSAF could lead to the development of novel fungicides or antifungal drugs.After the screening of culture media and fermentation conditions, L. enzymogenes C3was cultured three times on solid LB medium23L in total. The secondary metabolites were extracted and isolated to afford four compounds. Structure eludication on the basis of spectroscopic analysis revealed that compounds H-2and H-4were new PTMs, named3-deOH HSAF, and named H-4, respectively. Compounds H-1and H-3were known PTMs, named HSAF and Alteramide A, respectively. The OX4gene deletion mutant of L. enzymogenes C3was cultured on solid LB solid medium (10L), which afforded H-3and H-6. H-6was a new PTM, named3-deOH Alteramide A.Additionally, the isolation of secondary metabolites from four endophytic fungi produced8compounds. The fungal strain241was cultured on PDA medium (4L) to give two pyridone derivatives (2-1,2-2) and one sterol (2-3). Compound2-1was (-)-4,6’-anhydrooxysporidinone,2-2was (-)-oxysporidinone, and2-3was (22E,24R)-Cerevisterol. The strain A23was cultured on PDA medium (500mL), and two compounds (A-1, A-2) were obtained. Compound A-1was elucidated to be cytochalasin H, and compound A-2was a new one, named butyrylcytochalasin J. The strain F176was cultured on PDA medium (500mL) to produce two compounds (F-1, F-2). F-1was determined to be alternariol9-methyl ether, and F-2was alternariol. The Aspergillus flavipes was cultured on PDA medium to afford one compound, C-1, namely terphenyllin.The bioactivity of these compounds were studied. Compounds H-1and H-2showed antifungal activity against Rhizoctonia solani and Penicilium avellaneum.The in vitro anti-tumor activities of some compounds were measured against cancer cells by MTT method. The inhibition ratios against the growth of PC-3cells were45.9%,36.4%,80.9%and1.2%by compounds H-1, H-2, H-3and H-4at the concentration0.3μg/mL, respectively. A-1(1.0μg/ml) exhibited week cytotoxicity against HeLa and293T cells, the inhibition ratios were25.0%and32.8%. In conclusion, this dissertation indicated that microorganisms produce novel secondary metabolites, and are important resources for drug discovery and drug screening.