Chemical Investigations Of Five Strains Of Fungi And Their Biological Activities

Endophytic fungi are microorganisms that spend the whole or part of its life cycle colonizing inter-and/or intra-cellularly inside the healthy tissues,typically causing no apparent symptoms of disease.The long-term co-evolution between endophytic fungi and host plants can produce many secondary metabolites with novel structure and medicinal value that are the same or similar to those of host plants.As a new type of fungal resource in the study of natural products,animal-derived fungi have been rarely studied compared with other types of fungi.Due to its special living environment,rich biodiversity and the ability to produce novel metabolites with specific biological activity,they have a very broad research prospect.Therefore,the study on the chemical composition and biological activity of endophytic fungi and animal-derived fungi is a vital part of the research work on new drugs of natural products.In this study,thirty strains of fungi were cultured and purified from three plant samples and three animal samples.According to the results of strain identification combined with chemical composition analysis and preliminary activity screening,four strains of fungi with great research potential and one endolichenic fungus with certain research basis were selected as the target strains for subsequent research.Five strains of fungi from different sources,Xylaria sp.,Phialocephala fortinii,Penicillium citrinum,Aliiruegeria sabulilitoris and Talaromyces sp.,were amplified and fermented in rice medium,and extracted with ethyl acetate to obtain crude extract.Various separation methods such as silica gel column chromatography,ODS column chromatography,Medium Pressure Liquid column chromatography,Sephadex LH-20 column chromatography and reversed-phase high performance liquid chromatography were used to separate the crude extracts from rice fermentation.A total of 85 compounds were obtained,of which 23 were new compounds.In the process of structural identification,NMR,MS,UV,IR,ECD calculations and X-ray single crystal diffraction were used to determine the planar structure and absolute configuration of the obtained compounds.The antitumor,anti-inflammatory and antifungal activities of some compounds were tested.A chemical investigation of the endophytic fungus Xylaria sp.(No.ZW-1),which was isolated from the twigs of Cudrania tricuspidate,led to the discovery of thirty-five compounds,including five 2,5-diarylcyclopentenones(1a,1b,1c,2a and 2b),seven α-pyrone derivatives(3-9),one y-pyrone derivative(10),fifteen diketopiperazines(11-25),three isocoumarins(26-28),three other types of alkaloids(29-31),and one sesquiterpenoid(32),of which 1a-1c,2a,2b and 3-11 are new compounds.A plausible biosynthetic pathway of compounds 1 and 2 was proposed.HPLC-MS analysis was used to support that compounds 6-8 were produced by Xylaria sp..Furthermore,compounds 1a-11 were evaluated for potential antiproliferative activity against the human tumour cell lines PC3 and A549,and the results showed that 6 exhibited moderate inhibitory activity against the proliferation of PC3 cell lines with an IC50 value of 14.75,uM.Meanwhile,1c and 8 displayed weak inhibitory effects on NO production in RAW 264.7 murine macrophages with IC50 values of 49.76 and 69.68 μM,respectively.The second large-scale fermentation of endolichenic fungus Phialocephala fortinii(No.4537d)was carried out.Eight compounds were isolated from the more concentrated polar components of the new perylenequinones,including seven perylenequinone derivatives(33-39)and one spirobisnaphthalene(40).Compounds 33-37 are five new compounds.Cytotoxic activity results showed compounds 33,34,38 and 40 showed cytotoxic activities against EC 109 cells with IC50 values ranging from 24.5 to 33.3μM.Fourteen compounds were isolated from the moss endophytic fungus Penicillium citrinum(No.7-3),including two isocoumarins(41-42),four phenol derivatives(43-46),four monomer compounds of citrinin(47-50),one citrinin dimer(51),two steroids(52-53)and one dihydrogen α-pyranone derivative(54).Among these compounds,41 is a new compound.In addition,the compound 41 could reverse azole resistance of Candida albicans YEM 13 without obvious antifungal activity against Candida albicans SC5314 and YEM13,and reduce the MIC80 value of FLC to 8μg/mL when 41 was 16 μg/mL.Separation of the extract of symbiotic fungus Aliiruegeria sabulilitoris(No.SQ6-1)from the earthworm afforded eighteen compounds,including two polyketides with novel structure types(55-56),seven phenyl ethers(57-63),four other types of polyketides(64-67),two naphthalene derivatives(68-69)and three other simple aromatic compounds(70-72),of which compounds 55-57 are new.A plausible biosynthetic pathway of compounds 55 and 56 was proposed.The symbiotic fungus Talaromyces sp.(No.XZ-2)has been fermented,and ten known compounds were obtained from the crude extract,including one phenyl ether(73),one anthraquinone derivative(74),one isocoumarin(75),one cyclohexenone derivative(76)and six other types of aromatic compounds(77-82).Compound 79 was the natural product isolated for the first time.Bioactivity of the compounds showed that 77-79 could simultaneously enhance the sensitivity of Candida albicans YEM13 and YEM15 to FLC(FICI<0.5).In this study,the chemical compositions and biological activities of secondary metabolites of five fungi from different sources were investigated.A large number of natural products were isolated,some of which were new compounds,and some of which had significant biological activities.The above research results have enriched the studies on the metabolites of endophytic fungi and animal-derived fungi,indicating that they are important sources of novel active natural products,which need to be further studied and explored.