Induced biosyntheses of a novel butyrophenone and two aromatic polyketides in the plant pathogen Stagonospora nodorum

Fungal aromatic compounds comprise an important and structurally diverse group of secondary metabolites.Several genome sequencing projects revealed many putative biosynthetic gene clusters of fungal aromatic compounds,but many of these genes seem to be silent under typical laboratory culture conditions.To gain access to this untapped reservoir of natural products,we utilized chemical epigenetic modifiers to induce the expression of dormant biosynthetic genes.As a result,the concomitant supplementation of the histone deacetylase inhibitors suberoylanilide hydroxamic acid(500mM)and nicotinamide(50mM)to the culture medium of a fungal pathogen,Stagonospora nodorum,resulted in the isolation of three aromatic compounds(1-3),including a novel natural butyrophenone,(+)-4'-methoxy-(2S)-methylbutyrophenone(1),and two known polyketides,alternariol(2)and(-)-(3R)-mellein methyl ether(3).

The Combinatorial Biosynthesis of＂Unnatural＂ Products with Polyketides

Polyketides have been widely used clinically due to their significant biological activities, but the needed structural and functional diversity cannot be achieved by common chemical synthetic methods. The tool of combinatorial biosynthesis provides the possibility to produce "unnatural" natural drugs, which has achieved initial success. This paper provides an overview for the strategies of combinatorial biosynthesis in producing the structural and functional diversity of polyketides, including the redesign of metabolic flow, polyketide synthase(PKS) engineering, and PKS post-translational modification. Although encouraging progress has been made in the last decade, challenges still exist regarding the rational combinatorial biosynthesis of polyketides. In this review, the perspectives of polyketide combinatorial biosynthesis are also discussed.

Furan Derivatives and Polyketides from the Fungus Irpex lacteus

Eight new furan derivatives,irpexins A‒H(1‒8),two new polyketides,irpexins I and J(9 and 10),together with nine known compounds were isolated from the fermentation of Irpex lacteus.The structures and absolute configurations were elucidated on the basis of extensive spectroscopic methods and Mosher ester reaction.All compounds shows no cytotoxicity to human MCF-7 and Hela cancer cell lines at the concentration of 10μM.

Five new polyketides from the basidiomycete Craterellus odoratus

Five new polyketides,craterellones A-E(1-5),were isolated from cultures of basidiomycete Craterellus odoratus,together with five known compounds(6-10).Structures of 1-5 were elucidated on the basis of extensive spectroscopic analysis.All compounds were evaluated for their inhibitory activities against one isozyme of 11β-hydroxysteroid dehydrogenase(11β-HSD1)and cytotoxic activities on five tumor cell lines.Compound 10 exhibited significant cytotoxicity against HL-60,SMMC-7721,A-549,MCF-7,and SW-480,with IC50 values of 0.50,0.69,0.64,1.10,0.54μM,respectively.

Koninginins N-Q, Polyketides from the Endophytic Fungus Trichoderma koningiopsis Harbored in Panax notoginseng

Four new fungal polyketides named koninginins N-Q(1–4),together with four known analogues(5–8),were isolated from the endophytic fungus Trichoderma koningiopsis YIM PH30002 harbored in Panax notoginseng.Their structures were determined on the basis of spectral data interpretation.These compounds were evaluated for their antifungal activity,nitric oxide inhibition,and anticoagulant activity.

Asperochones A and B,two antimicrobial aromatic polyketides from the endophytic fungus Aspergillus sp.MMC-2

Two novel fungal metabolites,asperochones A and B,were obtained from an Aspergillus sp.Their structures were determined by 1D/2D nuclear magnetic resonance(NMR)spectroscopy,high resolution electrospray ionization mass spectroscopy(HRESIMS),and single-crystal X-ray diffraction analysis.Asperochone A possesses an intriguing skeleton bearing 5/6/6/6/7/5/5/5 octacyclic ring system,and asperochone B also exhibits an unusual carbon skeleton with five stereochiral centers.Their structures were proposed as heterotrimeric and heterodimeric products of aromatic polyketides.In addition,asperochone A exhibited a potential anti-tuberculosis effect since it showed a moderate potency against Mycobacterium smegmatis.

Editing function of type Ⅱ thioesterases in the biosynthesis of fungal polyketides

Polyketide synthases(PKSs)are megasynthases with multiple autonomously folding domains,which operate cooperatively in the PKS assemblies to synthesize specific polyketide scaffolds.Any nonreactive intermediates tethered to acyl carrier protein(ACP)domain in the PKS will block the elongation process of polyketide chains.In this study,we systematically elucidate the editing function of fungal typeⅡthioesterases(TEIIs)to hydrolyze ACP domain-bounded nonreactive acyl groups,which are uploaded by substrate promiscuous fungal phosphopantetheinyl transferase.Thereof,the TEIIs encoded in gene clusters of nonreducing PKS with reductase domain exhibit universal editing function.Besides,editing function was also found for TEIIs encoded in gene clusters of highly-reducing PKS with condensation domain.Hence,the editing TEIIs with function of recovery PKS are applied to improve the yield of the fungal polyketides in vivo.Our study provides valuable insights into the editing process of fungal PKSs,highlights the crucial role of TEIIs in enhancing polyketide production and introduces a novel metabolic engineering strategy for fungal polyketide biosynthesis by leveraging the editing function of TEIIs.

(+)/(-)-Mycosphatide A,a pair of highly oxidized polyketides with lipid-lowering activity from the mangrove endophytic fungus Mycosphaerella sp.SYSU-DZG01

(±)-Mycosphatide A(1a/1b),a pair of highly oxidized enantiomeric polyketides featuring a unique5/5/6/5-fused tetracyclic ring system,were isolated from the mangrove endophytic fungus Mycosphaerella sp.SYSU-DZG01.Their structures were established by extensive spectroscopic analyses,single crystal Xray diffraction,and experimental electronic circular dichroism(ECD)spectra comparison.The plausible biosynthetic pathway of 1 was proposed,which involved the generation of a key spiro[4.5]decane scaffold.Compounds(+)-1a and(-)-1b exhibited significant lipid-lowering activity in 3T3-L1 adipocytes model,with EC50values of 7.85±1.56 and 8.87±0.80μmol/L,respectively.

Discovery of angucyclinone polyketides from marine actinomycetes with a genomic DNA-based PCR assay targeting type Ⅱ polyketide synthase

Angucyclinones are aromatic polyketides produced by type Ⅱ polyketide synthases（PKS） and are mainly found in terrestrial actinomycetes. To discover more angucyclinones from marine actinomycetes, a genomic DNA-based PCR assay targeting type Ⅱ polyketide synthases was performed. Among the 167 marine actinomycetes strains screened, twelve strains were identified as the ＂positive＂ strains possessing type Ⅱ PKS-encoding genes based on the sequencing of PCR products. One of the 12 ＂positive＂ strains, Streptomyces sp. PKU-MA00218 was selected for the large-scale fermentation based on the HPLC and TLC analysis. Four angucyclinones, 6-deoxy-8-O-methylrabelomycin（1）, 8-O-methylrabelomycin（2）, 8-O-methyltetrangulol（3）, C-ring cleavage product of angucyclinone C（4）, were isolated and their structures were elucidated based on spectroscopic analyses. The isolation of angucyclinones 1–4 highlights the power of genome mining technologies based on biosynthetic knowledge in natural products discovery.

Diversified Polyketides and Nitrogenous Compounds from the Mangrove Endophytic Fungus Penicillium steckii SCSIO 41025

Four new polyketide decalin derivatives,penicisteck acids A-D(1-4),and three new nitrogenous compounds(7-9)z together with eight previously reported compounds,were isolated from the mangrove endophytic fungus Penicillium steckii SCSIO 41025.

Tripodalsporormielones A-C,unprecedented cage-like polyketides with complex polyvdent bridged and fused ring systems

A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bridged and fused ring systems.These polyketides with cage-like skeletons were characterized as a high non-protonated carbon-containing system,which resulted in few HMBC correlations observed and made the accurate structures hard to be obtained by NMR.Especially,some signals of non-protonated sp;carbons are weak and even unobservable in compound 1.In order to establish the structure of 1,the calculated NMR with DP4 evaluation was applied to determine the structure from the plausible structure candidates obtained from the detailed NMR analysis.Based on NMR experiments and calculated NMR,the structures of isolated compounds were established and confirmed by X-ray technology.Through chiral isolation,the optically pure enantiomers of 1 and 3 were obtained,and their absolute configurations were determined based on ECD quantum chemical calculation.Based on the isolated compounds and our previous work,1-3 would be derived from 3-methylorcinaldehyde,and their plausible biosynthetic mechanism was proposed.Furthermore,1 exhibited obvious short-term memory improvement activity on an Alzheimer’s disease fly model.

Peptides and polyketides isolated from the marine sponge-derived fungus Aspergillus terreus SCSIO 41008

Two new isomeric modified tripeptides,aspergillamides C and D(compounds 1 and 2),together with fifteen known compounds(compounds 3-17),were obtained from the marine sponge-derived fungus Aspergillus terreus SCSIO 41008.The structures of the new compounds,including absolute configurations,were determined by extensive analyses of spectroscopic data(NMR,MS,UV,and IR)and comparisons between the calculated and experimental electronic circular dichroism(ECD)spectra.Butyrolactone I(compound 11)exhibited strong inhibitory effects against Mycobacterium tuberculosis protein tyrosine phosphatase B(MptpB)with the IC_(50) being 5.11±0.53μmol·L^(–1),and acted as a noncompetitive inhibitor based on kinetic analysis.

Linear polyketides produced by co-culture of Penicillium crustosum and Penicillium fellutanum

Two new polyketides, penifellutins A (1) and B (2), possessing a 22 carbon linear skeleton, were isolated from a co-culture of the deep-sea-derived fungi Penicillium crustosum PRB-2 and Penicillium fellutanum HDN14-323. Meanwhile, two esterification products of 1, penifellutins C (3) and D (4), were obtained because compound 1 could be esterified spontaneously when stored in methanol. Their configurations were difficult to determine because of chiral central crowdedness, structural flexibility and instability. As such, we solved this issue by comprehensively using Mo2(OAc)4-based CD experiments, density functional theory calculation of 13C NMR, DP4 + probability analysis and many chemical reactions, including making acetonide derivative, Mosher’s method, PGME method, etc. Compounds 1 and 2 show obvious inhibitory activity on the liver hyperplasia of zebrafish larvae at a concentration of 10 μmol/L, while 3 and 4 show no activity, indicating that two carboxyls in the structure are important active sites.

Rational Engineering of Secondary Metabolic Pathways in a Heterologous Host to Enable the Biosynthesis of Hibarimicin Derivatives with Enhanced Anti-Melanomic Activity

A 61-kb biosynthetic gene cluster(BGC),which is accountable for the biosynthesis of hibarimicin(HBM)B from Microbispora rosea subsp.hibaria TP-A0121,was heterologously expressed in Streptomyces coelicolor M1154,which generated a trace of the target products but accumulated a large amount of shunt products.Based on rational analysis of the relevant secondary metabolism,directed engineering of the biosynthetic pathways resulted in the high production of HBM B,as well as new HBM derivates with improved antitumor activity.These results not only establish a biosynthetic system to effectively synthesize HBMs-a class of the largest and most complex Type-Ⅱpolyketides,with a unique pseudo-dimeric structure-but also set the stage for further engineering and deep investigation of this complex biosynthetic pathway toward potent anticancer drugs.

Antimicrobial Aromatic Polyketides from Gorgonian- Associated Fungus, Penicillium commune 518

Seven new aromatic polyketides, communols A-G （1-7）, were isolated and identified from the fermentation broth of Penicillium commune 518, a marine-derived fungus associated with the Gorgonian, Muricella abnormalis. The new structures of 1-7 were determined by spectroscopic analysis and X-ray single crystal diffraction. Among them, communol D （4） was the first example of a naturally occurring aromatic polyketide with a sulfoxide group from marine thngi. Compounds 1, 6, and 7 all showed moderate antimicrobial activities against Escherichia coli and Enterobacter aerogenes with MIC values of 4.1/16.4, 6.4/25.8, and 23.8/23.8μmoloL^-1, respectively.

Engineered polyketides:Synergy between protein and host level engineering

Metabolic engineering efforts toward rewiring metabolism of cells to produce new compounds often require the utilization of non-native enzymatic machinery that is capable of producing a broad range of chemical functionalities.Polyketides encompass one of the largest classes of chemically diverse natural products.With thousands of known polyketides,modular polyketide synthases(PKSs)share a particularly attractive biosynthetic logic for generating chemical diversity.The engineering of modular PKSs could open access to the deliberate production of both existing and novel compounds.In this review,we discuss PKS engineering efforts applied at both the protein and cellular level for the generation of a diverse range of chemical structures,and we examine future applications of PKSs in the production of medicines,fuels and other industrially relevant chemicals.

Three previously undescribed metabolites from Cordyceps cicadae JXCH-1,an entomopathogenic fungus

Three previously undescribed compounds,cordycicadione(1),cordycicadin F(2),and 7-hydroxybassiatin(3),were isolated from the cultures of Cordyceps cicadae JXCH1,an entomopathogenic fungus.Their structures and relative configurations were elucidated primarily by NMR spectroscopic analysis.The absolute configurations of 1 and 2 were determined by ECD calculations.Single-crystal X-ray diffraction method was adopted to determine the absolute configuration of 3.Compound 2 is a polycyclic polyketide with an unusual enol ether moiety and a spiro ring.The compounds obtained in this study were subjected to screening their inhibition against the proliferation of the human lung cancer cell line A549 and the production of nitric oxide in murine macrophages RAW264.7.

Talaketides A-G,linear polyketides with prostate cancer cytotoxic activity from the mangrove sediment-derived fungus Talaromyces sp.SCSIO 41027

Seven novel linear polyketides,talaketides A-G(1-7),were isolated from the rice media cultures of the mangrove sed-iment-derived fungus Talaromyces sp.SCSIO 41027.Among these,talaketides A-E(1-5)represented unprecedented unsaturated lin-ear polyketides with an epoxy ring structure.The structures,including absolute configurations of these compounds,were elucidated through detailed analyses of nuclear magnetic resonance(NMR)and high-resolution mass spectrometry(HR-MS)data,as well as elec-tronic custom distributors(ECD)calculations.In the cytotoxicity screening against prostate cancer cell lines,talaketide E(5)demon-strated a dose-dependent inhibitory effect on prostate cancer PC-3 cell lines,with an IC50 value of 14.44 μmol·L-1.Moreover,com-pound 5 significantly inhibited the cloning formation of PC-3 cell lines and arrested the cell cycle in S-phase,ultimately inducing ap-optosis.These findings indicate that compound 5 may serve as a promising lead compound for the development of a potential treat-ment for prostate cancer.

Multioxidized polyketides from an endophytic Penicillium sp.YUD17006 associated with Gastrodia elata

Three novel,highly oxygenated polyketides,multioketides A-C(1-3),and three previously described multioxidized aromatic polyketides(4-6),were isolated from an endophytic Penicillium sp.YUD17006 associated with Gastrodia elata.Their chem-ical structures were elucidated using extensive spectroscopic data,electronic circular dichroism calculations,and single X-ray diffrac-tion analysis.All metabolites were characterized by a typical α,β-unsaturated ketone fragment and exhibited a high degree of oxidation.Multioketides A and B were identified as a pair of epimers featuring a rare dihydroisobenzofuranone core.Multioketide C possessed a novel 5/6/6/6 heterotetracyclic chemical architecture with unusual 1,4-dioxin functionalities.Plausible biosynthetic pathways for 1-6 were proposed.Additionally,compound 3 demonstrated weak inhibitory activities against both acetylcholinesterase and protein tyr-osine phosphatase 1B.

Three New Compounds from the Actinomycete Actinocorallia aurantiaca

Aurantiadioic acids A(1)and B(2),two new furan-containing polyketides,and aurantoic acid A(3),a new natural product,were isolated from the liquid fermentation of the sika deer dung-derived actinomycete Actinocorallia aurantiaca.The structures of the new compounds were established by extensive spectroscopic methods,including 1D&2D NMR,HRESIMS spectroscopic analysis.The absolute configuration of 3 was assigned by comparison of the specific optical rotations with the reported derivatives.Biological activity evaluations suggested that compounds 1-3 showed weak inhibition on NO production in the murine monocytic RAW 264.7 macrophages with IC_(50)values of 35.8,41.8,45.2μM,respectively.Compound 3 showed weak inhibition on influenza A virus(A/PuertoRico/8/1934,H1N1)with an EC_(50)value of 35.9μM,and a selective index higher than 13.3.