Preliminary Study On Chemical Epigenetic Modification Of Two Fungi And Secondary Metabolites Of An Aspergillus Strain

Epigenetics is the study of heritable changes in gene activity that are not caused by changes in the DNA sequence.At present,the mainly used methods are eukaryotes histone acetylation and DNA demethylation.Therefore this idea is a new way to referenced to the eukaryotics microorganisms fungi to activating and expression the silencing gene.A total of 13 strains of endophytic fungi were evaluated for their modification of secondary metabolites by adding DNA methyltransferase inhibitors and histone deacetylase inhibitors.The method of TLC was used for detecting the constituents of the fermentation products.The secondary metabolites of two strains Phomopsis sp.YE3250 and Alternaria brassicae SYC36 were showed significant changes by adding different epigenetic modifiers.The above two strains were fermented by treating with epigenetic modifiers.The culture broths were extracted with ethyl acetate to give fermentation products,which were subjected to extensive silica gel and Sephadex LH-20 column chromatography.The structures of isolated compounds were determined by means of NMR and MS spectral analysis.Seven compounds were obtained from the culture broth of the strain Alternaria brassicae SYC36 treated with 200 ?M of sodium butyrate.Compound 1 was a new dimer of alternariol derivative,which was named as 4-epi-verralactone E.The TLC detection verified that compound 1 was only produced by inducing of the chemical epigenetic modifier sodium butyrate.The result showed that sodium butyrate could induce this strain to produce more complex chemical structure of metabolites.Six known compounds 2-7 were identified to be alterlactone(2),altenuene(3),djalonensone(4),alternaria(5),vomifoliol(6),and 7-hydroxy-3,5-dimethylisochromen-1-one(7).Three compounds were isolated from the culture broth of the strain Phomopsis sp.YE3250 treated with 200 ?M of nicotinamide.They were identified as 2-(carboxymet hyl)-3,5-dimethoxy-4-methylbenzoic acid(8),(1aS,3R,4R,4aR,6S,7R,8aS)-7-chloro-3,6-dihydroxy-3,4a,8,8-tetramethyl-octahydro-1aH-naphtho[1-b]oxirene-4-carbox-yli c acid(9),and orsellinic acid(10).Compound 8 is a new natural product,which was firstly obtained from nature.Compound 9 was a chlorine-containing sesquiterpene.In summary,we assumed that use of histone deacetylase inhibitor,such as sodium butyrate and nicotinamide can activate the expression of silent genes in endophytic fungi,showing its unique metabolic pathways,resulting in new compounds,which were different from those produced in normal culture conditions.Five compounds were obtained from the strain Aspergillus polyporicola CST11.They were determined to be 11-dehydro-curvularin(11),11?-hydroxy-curvularin(12),11?-methoxycurvulain(13),kipukasin I(14),and kipukasin C(15).Compounds 11-13 were belonging to curvularin derivative.Compounds 14-15 were belonging to nucleosides.The current results showed that curvularin derivatives were the main metabolites of this strain.