Chemical Epigenetic Regulation Of The Secondary Metabolites Of Three Fungi

Whole-genome sequencing has revealed that there are far more biosynthetic gene clusters than currently known metabolites from fungi,suggesting that the biosynthetic potential for natural products in fungi has been greatly under-explored by traditional methods of natural-product discovery.In addition to genetic manipulation and the alteration of the culturing condition by the One Strain Many Compounds(OSMAC)strategy,emerging evidence suggests that the secondary metabolism of fungi is regulated by epigenetics.Chemical epigenetic regulation can not only affect the yield of secondary metabolites,but also activate the "silent" secondary metabolites biosynthetic genes(clusters),thus enhancing the accumulation of secondary metabolites,and provide lead compounds for new drug development.In chapter 1,strategies for mining the structure diversities of of the fungal secondary metaboliteswere reviewed.In chapter 2,seven chemical epigenetic regulators(two DNA methyltransferase inhibitors,i.e.5-azacytidine,5-nitrogen-2-deoxycytosine nucleoside and five histone deacetylase inhibitors,i.e.SAHA,SBHA,sodium butyrate,valproate and nicotinamide)were studied for the regulating effect on the secondary metabolism of 20 fungal strains preserved in our laboratory.Comparative analyses of the secondary metabolite profiling by HPLC-DAD and TLC demonstrated that P.chrysogenum P1 X,Bjerkandera sp.,and P.chrysogenum HL were sensitive to the regulation of the histone deacetylase inhibitor SAHA.In chapter 3,P.chrysogenum P1 X,Bjerkandera sp.,and P.chrysogenum HL were selected for scaled-up studies(cultering media were supplemented with SAHA of a final concentration of 300 ?M).In the subsequent study,two induced products 1 and 2 were isolated and identified from P.chrysogenum P1 X with 1 being a new compound.Seven tremulane sesquiterpenes 3-9 and one ?-pyrone derivative 10 were produced by Bjerkandera sp.,of which 3-7 turned out to be induced products as indicated by comparative TLC analyses.To the best of our knowledge,it is the first report of tremulane sesquiterpenes from the fungal genus Bjerkandera.Three compounds 11-13 were purified from P.chrysogenum HL with 11 being an induced product.In summary,chemical epigenetic regulation of the fugal secondary metabolites was studied in the present work.SAHA was found to be the most effective among all the chemical epigenetic modifiers and exhibited the most significant regulating effect on P.chrysogenum P1 X,Bjerkandera sp.,and P.chrysogenum HL.Subsequentely,secondary metabolites of these three fungi(media supplemented with 300 ?M SAHA)were investigated and led to the isolation and identification of 13 comnpounds including 8 induced products(2 new compounds).In addition,the tremulane sesqueterpenoids were obtained from the fungal genus Bjerkandera sp.for the first time.Results of the present work indicated that chemical epigenetic modification could enhance the chemical diversity of fungal secondary metabolites,representing an effective method to produce fungal natural products with novel structures.