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A new aromatic polyketide, alternaphenol B2 (1), and four known compounds (2–5) were isolated from the coral-derived fungus Parengyodontium album SCSIO SX7W11. Their structures were elucidated by high-resolution mass spectrometry, 1D and 2D NMR spectroscopy and comparison with reported literatures. Compounds 1 and 2 exhibited selective inhibitory activity against isocitrate dehydrogenase mutant R132H (IDH1m), with IC50 values of 41.9 and 27.7 μM, respectively. Our findings thus provide a fresh incentive for investigation on IDH1m inhibitors as lead compounds for cancer treatment. [ABSTRACT FROM AUTHOR]

Angucyclines and angucyclinones represent a class of natural compounds that belong to the group of aromatic polyketides. They exhibit a wide array of biological properties, such as antimicrobial, antiviral, and cytotoxic. Their considerable therapeutic potential and diverse scaffolds have attracted many synthetic chemists to devise novel strategies to construct their intricate molecular architecture. Over 300 class members have been isolated from natural sources, mainly from bacterial strains of Streptomyces species. This review highlights recent advancements in their synthesis, such as oxidative cyclization, photooxidation, and metal‐catalyzed [4+2]‐cycloaddition, which has facilitated the efficient and practical total syntheses of various angucycline and angucyclinone natural products. [ABSTRACT FROM AUTHOR]

An investigation of ×19 soil samples collected under the auspices of the Australian citizen science initiative, Soils for Science, returned ×559 chemically dereplicated microbial isolates, of which ×54 exhibited noteworthy anthelmintic activity against either the heartworm Dirofilaria immitis microfilaria and/or the gastrointestinal parasite Haemonchus contortus L1–L3 larvae. Chemical (GNPS and UPLC-DAD) and cultivation (MATRIX) profiling prompted a detailed chemical investigation of Streptomyces sp. S4S-00196A10, which yielded new anthelmintic polyketide goondapyrones A–J (1–10), together with the known actinopyrones A (11) and C (12). Structures for 1–12 were assigned on the basis of detailed spectroscopic and chemical analysis, with preliminary structure activity relationship analysis revealing selected γ-pyrones >50-fold and >13-fold more potent than isomeric α-pyrones against D. immitis mf motility (e.g., EC50 0.05 μM for 1; EC50 2.7 μM for 5) and H. contortus L1–L3 larvae development (e.g., EC50 0.58 μM for 1; EC50 8.2 μM for 5), respectively. [ABSTRACT FROM AUTHOR]

Marine-derived Aspergillus sp. strain w2-13, isolated from Dongshan Island in Fujian Province, produced five compounds through solid-state fermentation. This included a new polyketide, aspilactonol J (1), and four previously identified compounds (2-5). The structure of the new compound was determined using NMR, HRMS, and ECD, supported by theoretical calculations. A plausible biosynthetic pathway for polyketides 1-3 was also proposed. Cytotoxicity tests on various cancer cell lines revealed that aspilactonol J (1) exhibited significant selectivity and efficacy, especially against HepG2 cells, suggesting its potential for pharmaceutical development. This study highlights the role of marine fungi as valuable sources of bioactive natural products with therapeutic potential. [ABSTRACT FROM AUTHOR]

A new compound, comazaphilone I (1), was isolated from Mycolicibacterium aurum WYQ isolated from marine sediment samples collected in the East China Sea. Its structure was elucidated based on spectroscopic data, comparison with literature data, and ECD calculation. The newly discovered compound, while bearing a similar planar structure to the known compound comazaphilone A, features a distinct 6S7S configuration. However, no bioactivities were screened from the bioassay experiments. [ABSTRACT FROM AUTHOR]

One novel polyketide, fusaritide A (1), was isolated from a marine fish-derived halotolerant fungal strain Fusarium verticillioide G102. The structure was determined through extensive spectroscopic analysis and high-resolution electrospray ionization mass spectrometry. Fusaritide A (1) with unprecedented structure reduced cholesterol uptake by inhibiting Niemann-Pick C1-Like 1 (NPC1L1). [ABSTRACT FROM AUTHOR]

Twelve compounds, including four undescribed cytochalasins, xylariachalasins A–D (1–4), four undescribed polyketides (5–8), and four known cytochalasins (9–12), were isolated from the mangrove endophytic fungus Xylaria arbuscula QYF. Their structures and absolute configurations were established by extensive spectroscopic analyses (1D and 2D NMR, HRESIMS), electronic circular dichroism (ECD) calculations, 13C NMR calculation and DP4+ analysis, single-crystal X-ray diffraction, and the modified Mosher ester method. Compounds 1 and 2 are rare cytochalasin hydroperoxides. In bioactivity assays, Compound 2 exhibited moderate antimicrobial activities against Staphylococcus aureus and Candida albicans with MIC values of 12.5 μM for both Compound 10 exhibited significant cytotoxic activity against MDA-MB-435 with an IC50 value of 3.61 ± 1.60 μM. [ABSTRACT FROM AUTHOR]

Three new polyketides, including three ester derivatives (1, 3, and 5) and a new natural product, which was a benzoquinone derivative, embelin A (4), together with nine known ones (2 and 6–13), were isolated from the mangrove-derived fungus Penicillium sp. SCSIO 41411. Their structures were determined by detailed NMR and MS spectroscopic analyses. The X-ray single-crystal diffraction analysis of 4 was described for the first time. Compound 9 displayed obvious inhibition against PDE4 with an inhibitory ratio of 40.78% at 10 μM. Compound 12 showed DPPH radical scavenging activity, with an EC50 of 16.21 µg/mL, compared to the positive control (ascorbic acid, EC50, 11.22 µg/mL). Furthermore, compound 4 exhibited cytotoxicity against PC-3 and LNCaP with IC50 values of 18.69 and 31.62 µM, respectively. [ABSTRACT FROM AUTHOR]

Microbial‐derived natural products remain a major source of structurally diverse bioactive compounds and chemical scaffolds that have the potential as new therapeutics to target drug‐resistant pathogens and cancers. In particular, genome mining has revealed the vast number of cryptic or low‐yield biosynthetic gene clusters in the genus Streptomyces. However, low natural product yields—improvements to which have been hindered by the lack of high throughput methods—have slowed the discovery and development of many potential therapeutics. Here, we describe our efforts to improve yields of landomycins—angucycline family polyketides under investigation as cancer therapeutics—by a genetically modified Streptomyces cyanogenus 136. After simplifying the extraction process from S. cyanogenus cultures, we identified a wavelength at which the major landomycin products are absorbed in culture extracts, which we used to systematically explore culture medium compositions to improve total landomycin titers. Through correlational analysis, we simplified the culture optimization process by identifying an alternative wavelength at which culture supernatants absorb yet is representative of total landomycin titers. Using the subsequently improved sample throughput, we explored landomycin production during the culturing process to further increase landomycin yield and reduce culture time. Testing the antimicrobial activity of the isolated landomycins, we report broad inhibition of Gram‐positive bacteria, inhibition of fungi by landomycinone, and broad landomycin resistance by Gram‐negative bacteria that is likely mediated by the exclusion of landomycins by the bacterial membrane. Finally, the anticancer activity of the isolated landomycins against A549 lung carcinoma cells agrees with previous reports on other cell lines that glycan chain length correlates with activity. Given the prevalence of natural products produced by Streptomyces, as well as the light‐absorbing moieties common to bioactive natural products and their metabolic precursors, our method is relevant to improving the yields of other natural products of interest. [ABSTRACT FROM AUTHOR]

Three decades of studies on the multifunctional 6-deoxyerythronolide B synthase have laid a foundation for understanding the chemistry and evolution of polyketide antibiotic biosynthesis by a large family of versatile enzymatic assembly lines. Recent progress in applying chemical and structural biology tools to this prototypical assembly-line polyketide synthase (PKS) and related systems has highlighted several features of their catalytic cycles and associated protein dynamics. There is compelling evidence that multiple mechanisms have evolved in this enzyme family to channel growing polyketide chains along uniquely defined sequences of 10–100 active sites, each of which is used only once in the overall catalytic cycle of an assembly-line PKS. Looking forward, one anticipates major advances in our understanding of the mechanisms by which the free energy of a repetitive Claisen-like reaction is harnessed to guide the growing polyketide chain along the assembly line in a manner that is kinetically robust yet evolutionarily adaptable. [ABSTRACT FROM AUTHOR]

Two new polyketide derivatives, penirubenones A and B (1 and 2), and two naturally rare amino-bis-tetrahydrofuran derivatives, penirubenamides A and B (3 and 4), together with nine known compounds (5–13) were isolated from the marine-derived fungus Penicillium rubens BTBU20213035. The structures were identified by HRESIMS and 1D and 2D NMR analyses, and their absolute configurations were determined by a comparison of experimental and calculated electronic circular dichroism (ECD) spectroscopy and 13C NMR data. We found that 6 exhibited antibacterial activity against Staphylococcus aureus, with an MIC value of 3.125 μg/mL, and 1 and 2 showed synergistic antifungal activity against Candida albicans at 12.5 and 50 μg/mL with 0.0625 μg/mL rapamycin. [ABSTRACT FROM AUTHOR]

A pair of new epimeric polyketides, named albifimbrins A and B (1 and 2), were isolated from the cultures of the shellfish-derived fungus Albifimbria verrucaria CD1–4. Their structures were determined by extensive spectroscopic analysis including HR-MS, 1D and 2D NMR data, together with the CD exciton chirality method. Compounds 1 and 2 possess unusual tetrahydrofuran moiety in their linear molecule structures. The antimicroalgal assay indicated that compounds 1 and 2 shown moderate inhibitory activities against marine harmful microalgae, Prorocentrum donghaiense , Amphidinium carterae and Heterocapsa circulariaquama. [Display omitted] • A pair of new epimeric polyketide derivatives from the marine-derived fungus Albifimbria verrucaria CD1–4. • Their structures were elucidated by NMR, HR-MS and CD exciton chirality expeirments. • The isolates displayed moderate inhibitory activities against some marine microalgal species. [ABSTRACT FROM AUTHOR]

Mangrove-associated endophytic fungi are producers of secondary metabolites in unique and diverse structures with interesting biological activities such as antiviral, antifungal, antibacterial, anti-inflammatory, and cytotoxic agents. Endophytes play an important role in the physiological activities of the host plants, influencing the improvement of resistance to stress, insects, nematodes, and diseases. In this study, arohynapene A, a polyketide compound, was successfully isolated from the mangrove-derived fungus Penicillium steckii JB-NW-2-1 obtained from mangrove plant Avicennia marina (Forssk) Vierh. The structure was determined by a spectroscopic method including IR, MS, 1D-, and 2D-NMR techniques. This compound was evaluated for cytotoxic activities using resazurin assay against four cancer cells, HeLa cervical, MCF-7 breast cancer, B16-F10 melanoma, and A549 lung adenocarcinoma. The results showed no significant activities against all cancer cells tested (IC50 > 500 µM).

Amphidinolides C, F, and U, including C2‐C4 analogs, are highly cytotoxic marine macrolides, mainly isolated from dinoflagellates of the genus Amphidinium. All these polyketides share a 75 % or more similar structure, highlighted by a macrolactone ring, at least one trans‐2,5‐substituted‐THF motif and a characteristic polyenic side chain. From their isolation and absolute configurational assignment, the total synthesis of these marine macrolides represented an intense challenge to the organic synthesis community over the last 15 years, with around 14 research groups engaged in this inspiring task. In the first part of this review, we present the different approaches to the isolation and characterization of these natural products, including the most recent analogs, which may cast doubt on the biogenetic origin of these compounds. The various synthetic approaches to the total synthesis of C, F, and U amphidinolides are presented in a second part, focusing on key reactions and/or innovative strategies. The review concludes in a third section summarizing the successful approaches leading to the total synthesis of one of the members of this amphidinolide subfamily. [ABSTRACT FROM AUTHOR]

Aromatic polyketides are renowned for their wide-ranging pharmaceutical activities. Their structural diversity is mainly produced via modification of limited types of basic frameworks. In this study, we characterized the biosynthesis of a unique basic aromatic framework, phenyldimethylanthrone (PDA) found in (+)/(-)-anthrabenzoxocinones (ABXs) and fasamycin (FAS). Its biosynthesis employs a methyltransferase (Abx(+)M/ Abx(-)M/FasT) and an unusual TcmI-like aromatase/cyclase (ARO/CYC, Abx(+)D/ Abx(-)D/FasL) as well as a nonessential helper ARO/CYC (Abx(+)C/Abx(-)C/FasD) to catalyze the aromatization/cyclization of polyketide chain, leading to the formation of all four aromatic rings of the PDA framework, including the C9 to C14 ring and a rare angular benzene ring. Biochemical and structural analysis of Abx(+)D reveals a unique loop region, giving rise to its distinct acyl carrier protein-dependent specificity compared to other conventional TcmI-type ARO/CYCs, all of which impose on free molecules. Mutagenic analysis discloses critical residues of Abx(+)D for its catalytic activity and indicates that the size and shape of its interior pocket determine the orientation of aromatization/cyclization. This study unveils the tetracyclic and non-TcmN type C9 to C14 ARO/CYC, significantly expanding our cognition of ARO/CYCs and the biosynthesis of aromatic polyketide framework. [ABSTRACT FROM AUTHOR]

During the life activities of microorganisms, a variety of secondary metabolites are produced, including antimicrobials and antitumor drugs, which are widely used in clinical practice. In addition to exploring new antibiotics, this makes it one of the research priorities of Actinomycetes to effectively increase the yield of antibiotics in production strains by various means. Most antibiotic-producing strains have a variety of functional regulatory factors that regulate their growth, development, and secondary metabolite biosynthesis processes. Through the study of precursor substances in antibiotic biosynthesis, researchers have revealed the precursor biosynthesis process and the mechanism by which precursor synthesis regulators affect the biosynthesis of secondary metabolites, which can be used to obtain engineered strains with high antibiotic production. This paper summarizes the supply of antibiotic biosynthesis precursors and the progress of research on the role of regulators in the process of precursors in biosynthesis. This lays the foundation for the establishment of effective breeding methods to improve antibiotic yields through the manipulation of precursor synthesis genes and related regulators. [ABSTRACT FROM AUTHOR]

Type II polyketide synthase (PKS) systems are a rich source of structurally diverse polycyclic aromatic compounds with clinically relevant antibiotic and chemotherapeutic properties. The enzymes responsible for synthesizing the polyketide core, known collectively as the minimal cassette, hold potential for applications in synthetic biology. The minimal cassette provides polyketides of different chain lengths, which interact with other enzymes that are responsible for the varied cyclization patterns. Additionally, the type II PKS enzyme clusters offer a wide repertoire of tailoring enzymes for oxidations, glycosylations, cyclizations, and rearrangements. This review begins with the variety of chemical space accessible with type II PKS systems including the recently discovered highly reducing variants that produce polyalkenes instead of the archetypical polyketide motif. The main discussion analyzes the previous approaches with an emphasis on further research that is needed to characterize the minimal cassette enzymes in vitro. Finally, the potential type II PKS systems hold the potential to offer new tools in biocatalysis and synthetic biology, particularly in the production of novel antibiotics and biofuels. [ABSTRACT FROM AUTHOR]

TA4-1 is the type strain of Streptomyces chiangmaiensis. The TA4-1 strain was isolated from a stingless bee (Tetragonilla collina). Here we present the draft genome sequence data of S. chiangmaiensis TA4-1. The Illumina NextSeq 550 sequencer was used to generate paired-end reads from the genomic DNA of the pure culture of S. chiangmaiensis TA4-1. The draft genome sequence of strain TA4-1 consists of 776 contigs with a total size of 9,707,984 base pairs, an N50 of 32,937 base pairs, and a GC content of 69.73 %. Digital DNA-DNA hybridisation (dDDH) and average nucleotide identity (ANI) analysis showed that S. yaanensis CGMCC 4.7035 had the highest dDDH value (32.7 %) and ANIm value (88.50 %) when compared with TA4-1. The presented data indicate thepotential for a reference genome sequence in bacterial taxonomy, comparative genomics, and the investigation of bioactive compound biosynthesis in S. chiangmaiensis TA4-1. The draft genome sequence data have been deposited at NCBI under the Bioproject accession number PRJNA680432.

Abstract Marine-derived fungi of the genus Trichoderma have been surveyed for pharmaceuticals and agrochemicals since 1993, with various new secondary metabolites being characterized from the strains of marine animal, plant, sediment, and water origin. Chemical structures and biological activities of these metabolites are comprehensively reviewed herein up to the end of 2022 (covering 30 years). More than 70 strains that belong to at least 18 known Trichoderma species have been chemically investigated during this period. As a result, 445 new metabolites, including terpenes, steroids, polyketides, peptides, alkaloids, and others, have been identified, with over a half possessing antimicroalgal, zooplankton-toxic, antibacterial, antifungal, cytotoxic, anti-inflammatory, and other activities. The research is highlighted by the molecular diversity and antimicroalgal potency of terpenes and steroids. In addition, metabolic relevance along with co-culture induction in the production of new compounds is also concluded. Trichoderma strains of marine origin can transform and degrade heterogeneous molecules, but these functions need further exploration. Graphical Abstract

4-Hydroxy-2-pyrones are of interest as potential biorenewable molecules for a sustainable transition from biomass feedstock to valuable chemical products. This review focuses on the methodologies for the synthesis of 4-hydroxy-2-pyrones published over the last 20 years. These pyrones as polyketides are widespread in Nature and possess versatile bioactivity that makes them an attractive target for synthesis and modification. Biosynthetic paths of the pyrones are actively developed and used as biotechnological approaches for the construction of natural and unnatural polysubstituted 4-hydroxy-2-pyrones. The major synthetical methods are biomimetic and are based on the cyclization of tricarbonyl compounds. Novel chemical methods of de novo synthesis based on alkyne cyclizations using transition metal complexes and ketene transformations allow for straightforward access to 4-hydroxy-2-pyrones and have been applied for the construction of natural products. Possible directions for further pyrone ring modification are discussed.

An investigation of ×19 soil samples collected under the auspices of the Australian citizen science initiative, Soils for Science, returned ×559 chemically dereplicated microbial isolates, of which ×54 exhibited noteworthy anthelmintic activity against either the heartworm Dirofilaria immitis microfilaria and/or the gastrointestinal parasite Haemonchus contortus L1–L3 larvae. Chemical (GNPS and UPLC-DAD) and cultivation (MATRIX) profiling prompted a detailed chemical investigation of Streptomyces sp. S4S-00196A10, which yielded new anthelmintic polyketide goondapyrones A–J (1–10), together with the known actinopyrones A (11) and C (12). Structures for 1–12 were assigned on the basis of detailed spectroscopic and chemical analysis, with preliminary structure activity relationship analysis revealing selected γ-pyrones >50-fold and >13-fold more potent than isomeric α-pyrones against D. immitis mf motility (e.g., EC50 0.05 μM for 1; EC50 2.7 μM for 5) and H. contortus L1–L3 larvae development (e.g., EC50 0.58 μM for 1; EC50 8.2 μM for 5), respectively.

Twelve compounds, including four undescribed cytochalasins, xylariachalasins A–D (1–4), four undescribed polyketides (5–8), and four known cytochalasins (9–12), were isolated from the mangrove endophytic fungus Xylaria arbuscula QYF. Their structures and absolute configurations were established by extensive spectroscopic analyses (1D and 2D NMR, HRESIMS), electronic circular dichroism (ECD) calculations, 13C NMR calculation and DP4+ analysis, single-crystal X-ray diffraction, and the modified Mosher ester method. Compounds 1 and 2 are rare cytochalasin hydroperoxides. In bioactivity assays, Compound 2 exhibited moderate antimicrobial activities against Staphylococcus aureus and Candida albicans with MIC values of 12.5 μM for both Compound 10 exhibited significant cytotoxic activity against MDA-MB-435 with an IC50 value of 3.61 ± 1.60 μM.

Six new polyketides, which includes three new lactones (talarotones A-C) (1-3), one new polyketide (talarotide A) (4), two new polyenes (talaroyenes A, B) (5, 6), together with one new meroterpenoid (talaropenoid A) (7) and 13 known compounds (8-20) were isolated from the mangrove-derived fungus Talaromyces flavus TGGP35. The structure and configuration of the compounds 1-7 were elucidated from the data obtained from HR-ESI-MS, IR, 1D/2D NMR spectroscopy, Mo2 (OAc)4-induced electronic circular dichroism (ECD), CD spectroscopy, and modified Mosher's method. Compounds 5 and 20 displayed antioxidant activity with IC50 values of 0.40 and 1.36mM, respectively. Compounds 3, 6, 11, 16, and 17 displayed cytotoxic activity against human cancer cells Hela, A549, and had IC50 values ranging from 28.89 to 62.23 µM. Compounds 7, 10-12, and 14-18 exhibited moderate or potent anti-insect activity against newly hatched larvae of Helicoverpa armigera Hubner, with IC50 values in the range 50-200µg/mL. Compound 18 showed antibacterial activity against Ralstonia solanacearum with the MIC value of 50 µg/mL.. [ABSTRACT FROM AUTHOR]

Wild-type Aspergillus nidulans asexual spores (conidia) are green due to a pigment that protects the spores against ultraviolet light. The pigment is produced by a biosynthetic pathway, the genes of which are dispersed in the genome. The backbone molecule of the pigment is a polyketide synthesized by a polyketide synthase encoded by the wA gene. If wA is not functional, the conidia are white. The polyketide is modified by a laccase encoded by the yA gene and inactivation of yA in an otherwise wild-type background results in yellow spores. Additional spore color mutations have been isolated and mapped to a locus genetically, but the genes that correspond to these loci have not been determined. Spore color markers have been useful historically, and they remain valuable in the molecular genetics era. One can determine if a transforming fragment has been successfully integrated at the wA or yA locus by simply looking at the color of transformant conidia. The genes of the potentially useful color loci chaA (chartreuse conidia) and fwA (fawn conidia) have not been identified previously. We chose a set of candidate genes for each locus by comparing the assembled genome with the genetic map. By systematically deleting these candidate genes, we identified a cytochrome P450 gene (AN10028) corresponding to chaA. Deletions of this gene result in chartreuse conidia and chartreuse mutations can be complemented in trans by a functional copy of this gene. With fwA, we found that the existing fawn mutation, fwA1, is a deletion of 2241 base pairs that inactivates three genes. By deleting each of these genes, we determined that fwA is AN1088, an EthD domain protein. Deletion of AN1088 results in fawn conidia as expected. Neither deletion of chaA nor fwA restricts growth and both should be valuable target loci for transformations. Combinations of deletions have allowed us to investigate the epistasis relationships of wA, yA, chaA and fwA. [ABSTRACT FROM AUTHOR]

In this study, two previously undescribed nitrogen-containing compounds, penisimplicins A (1) and B (2), were isolated from Penicillium simplicissimum JXCC5. The structures of 1 and 2 were elucidated on the basis of comprehensive spectroscopic data analysis, including 1D and 2D NMR and HRESIMS data. The absolute configuration of 2 was determined by Marfey's method, ECD calculation, and DP4+ analysis. Both structures of 1 and 2 feature an unprecedented manner of amino acid-derivatives attaching to a polyketide moiety by C-C bond. The postulated biosynthetic pathways for 1 and 2 were discussed. Additionally, compound 1 exhibited significant acetylcholinesterase inhibitory activity, with IC50 values of 6.35 μM. [ABSTRACT FROM AUTHOR]

Marine-derived fungi of the genus Trichoderma have been surveyed for pharmaceuticals and agrochemicals since 1993, with various new secondary metabolites being characterized from the strains of marine animal, plant, sediment, and water origin. Chemical structures and biological activities of these metabolites are comprehensively reviewed herein up to the end of 2022 (covering 30 years). More than 70 strains that belong to at least 18 known Trichoderma species have been chemically investigated during this period. As a result, 445 new metabolites, including terpenes, steroids, polyketides, peptides, alkaloids, and others, have been identified, with over a half possessing antimicroalgal, zooplankton-toxic, antibacterial, antifungal, cytotoxic, anti-inflammatory, and other activities. The research is highlighted by the molecular diversity and antimicroalgal potency of terpenes and steroids. In addition, metabolic relevance along with co-culture induction in the production of new compounds is also concluded. Trichoderma strains of marine origin can transform and degrade heterogeneous molecules, but these functions need further exploration. [ABSTRACT FROM AUTHOR]

Three central steps during the biosynthesis of cytochalasan precursors, including reductive release, Knoevenagel cyclisation and Diels Alder cyclisation are not yet understood at a detailed molecular level. In this work we investigated the reductive release step catalysed by a hybrid polyketide synthase non‐ribosomal peptide synthetase (PKS‐NRPS) from the pyrichalasin H pathway. Synthetic thiolesters were used as substrate mimics for in vitro studies with the isolated reduction (R) and holo‐thiolation (T) domains of the PKS‐NRPS hybrid PyiS. These assays demonstrate that the PyiS R‐domain mainly catalyses an NADPH‐dependent reductive release of an aldehyde intermediate that quickly undergoes spontaneous Knoevenagel cyclisation. The R‐domain can only process substrates that are covalently bound to the phosphopantetheine thiol of the upstream T‐domain, but it shows little selectivity for the polyketide. [ABSTRACT FROM AUTHOR]

Where does one draw the line between primary and secondary metabolism? The answer depends on the perspective. Microbial secondary metabolites (SMs) were at first believed not to be very important for the producers because they are dispensable for growth under laboratory conditions. However, such compounds become important in natural niches of the organisms, and some are of prime importance for humanity. Polyketides are an important group of SMs with aflatoxin as a well‐known and well‐characterized example. In Aspergillus spp., all 34 afl genes encoding the enzymes for aflatoxin biosynthesis are located in close vicinity on chromosome III in a so‐called gene cluster. This led to the assumption that most genes required for polyketide biosynthesis are organized in gene clusters. Recent research, however, revealed an enormous complexity of the biosynthesis of different polyketides, ranging from individual polyketide synthases to a gene cluster producing several compounds, or to several clusters with additional genes scattered in the genome for the production of one compound. Research of the last decade furthermore revealed a huge potential for SM biosynthesis hidden in fungal genomes, and methods were developed to wake up such sleeping genes. The analysis of organismic interactions starts to reveal some of the ecological functions of polyketides for the producing fungi. [ABSTRACT FROM AUTHOR]

Gracilioether M (6) and 11,12-dihydrogracilioether M (7), two polyketides with a [2(5H)-furanylidene]ethanoate moiety, along with known plakortone G (9) and its new naturally occurring derivative 9,10-dihydroplakortone G (8), were isolated from the Caribbean marine sponge Plakortis halichondrioides. The structures and absolute configuration of 6, 7, and 8 were characterized by analysis of HRESIMS and NMR spectroscopic data, chemical derivatization, and side-by-side comparisons with published NMR data of related analogs. Compounds 6 and 7 and a mixture of 8 and 9 were evaluated for cytotoxicity against MCF-7 human breast cancer cells. In addition, the in vitro antiplasmodial activity against Plasmodium berghei of these compounds was scrutinized using a drug luminescence assay. [ABSTRACT FROM AUTHOR]

Chemical epigenetic cultivation of the sponge-derived fungus Pestalotiopsis sp. SWMU-WZ04-1 contributed to the identification of twelve polyketide derivatives, including six new pestalotiopols E–J (1–6) and six known analogues (7–12). Their gross structures were deduced from 1D/2D NMR and HRESIMS spectroscopic data, and their absolute configurations were further established by circular dichroism (CD) Cotton effects and the modified Mosher's method. In the bioassay, the cytotoxic and antibacterial activities of all compounds were evaluated. Chlorinated benzophenone derivatives 7 and 8 exhibited inhibitory effects on Staphylococcus aureus and Bacillus subtilis, with MIC values varying from 3.0 to 50 μg/mL. In addition, these two compounds were cytotoxic to four types of human cancer cells, with IC50 values of 16.2~83.6 μM. The result showed that compound 7 had the probability of being developed into a lead drug with antibacterial ability. [ABSTRACT FROM AUTHOR]

Koninginins X-Z (1–3), three novel polyketides, were isolated from the solid fermentation of the endophytic fungus Trichoderma koningiopsis SC-5. Their structures, including the absolute configurations, were comprehensively characterized by a combination of NMR spectroscopic methods, HRESIMS, 13C NMR, DFT GIAO 13C NMR, and electronic circular dichroism calculations as well as single crystal X-ray diffraction. In addition, all the compounds were evaluated for antifungal activity against Candida albicans. [ABSTRACT FROM AUTHOR]

4-Hydroxy-2-pyrones are of interest as potential biorenewable molecules for a sustainable transition from biomass feedstock to valuable chemical products. This review focuses on the methodologies for the synthesis of 4-hydroxy-2-pyrones published over the last 20 years. These pyrones as polyketides are widespread in Nature and possess versatile bioactivity that makes them an attractive target for synthesis and modification. Biosynthetic paths of the pyrones are actively developed and used as biotechnological approaches for the construction of natural and unnatural polysubstituted 4-hydroxy-2-pyrones. The major synthetical methods are biomimetic and are based on the cyclization of tricarbonyl compounds. Novel chemical methods of de novo synthesis based on alkyne cyclizations using transition metal complexes and ketene transformations allow for straightforward access to 4-hydroxy-2-pyrones and have been applied for the construction of natural products. Possible directions for further pyrone ring modification are discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT Cervimycins A–D are bis-glycosylated polyketide antibiotics produced by Streptomyces tendae HKI 0179 with bactericidal activity against Gram-positive bacteria. In this study, cervimycin C (CmC) treatment caused a spaghetti-like phenotype in Bacillus subtilis 168, with elongated curved cells, which stayed joined after cell division, and exhibited a chromosome segregation defect, resulting in ghost cells without DNA. Electron microscopy of CmC-treated Staphylococcus aureus (3 × MIC) revealed swollen cells, misshapen septa, cell wall thickening, and a rough cell wall surface. Incorporation tests in B. subtilis indicated an effect on DNA biosynthesis at high cervimycin concentrations. Indeed, artificial downregulation of the DNA gyrase subunit B gene (gyrB) increased the activity of cervimycin in agar diffusion tests, and, in high concentrations (starting at 62.5 × MIC), the antibiotic inhibited S. aureus DNA gyrase supercoiling activity in vitro. To obtain a more global view on the mode of action of CmC, transcriptomics and proteomics of cervimycin treated versus untreated S. aureus cells were performed. Interestingly, 3 × MIC of cervimycin did not induce characteristic responses, which would indicate disturbance of the DNA gyrase activity in vivo. Instead, cervimycin induced the expression of the CtsR/HrcA heat shock operon and the expression of autolysins, exhibiting similarity to the ribosome-targeting antibiotic gentamicin. In summary, we identified the DNA gyrase as a target, but at low concentrations, electron microscopy and omics data revealed a more complex mode of action of cervimycin, which comprised induction of the heat shock response, indicating protein stress in the cell.IMPORTANCEAntibiotic resistance of Gram-positive bacteria is an emerging problem in modern medicine, and new antibiotics with novel modes of action are urgently needed. Secondary metabolites from Streptomyces species are an important source of antibiotics, like the cervimycin complex produced by Streptomyces tendae HKI 0179. The phenotypic response of Bacillus subtilis and Staphylococcus aureus toward cervimycin C indicated a chromosome segregation and septum formation defect. This effect was at first attributed to an interaction between cervimycin C and the DNA gyrase. However, omics data of cervimycin treated versus untreated S. aureus cells indicated a different mode of action, because the stress response did not include the SOS response but resembled the response toward antibiotics that induce mistranslation or premature chain termination and cause protein stress. In summary, these results point toward a possibly novel mechanism that generates protein stress in the cells and subsequently leads to defects in cell and chromosome segregation.

Abstract 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. Graphical Abstract

Abstract Background Endophytic fungi have proven to be a rich source of novel natural products with a wide-array of biological activities and higher levels of structural diversity. Results Chemical investigation on the liquid- and solid-state fermented products of Chaetomium globosum Km1226 isolated from the littoral medicinal herb Atriplex maximowicziana Makino resulted in the isolation of compounds 1–14. Their structures were determined by spectroscopic analysis as three previously undescribed C13-polyketides, namely aureonitol C (1), mollipilins G (2), and H (3), along with eleven known compounds 4–14. Among these, mollipilin A (5) exhibited significant nitric oxide production inhibitory activity in LPS-induced BV-2 microglial cells with an IC50 value of 0.7 ± 0.1 µM, and chaetoglobosin D (10) displayed potent anti-angiogenesis property in human endothelial progenitor cells (EPCs) with an IC50 value of 0.8 ± 0.3 µM. Conclusions Three previously unreported compounds 1–3 were isolated and identified. Mollipilin A (5) and chaetoglobosin D (10) could possibly be developed as anti-inflammatory and anti-angiogenic lead drugs, respectively.

Three new polyketides, including three ester derivatives (1, 3, and 5) and a new natural product, which was a benzoquinone derivative, embelin A (4), together with nine known ones (2 and 6–13), were isolated from the mangrove-derived fungus Penicillium sp. SCSIO 41411. Their structures were determined by detailed NMR and MS spectroscopic analyses. The X-ray single-crystal diffraction analysis of 4 was described for the first time. Compound 9 displayed obvious inhibition against PDE4 with an inhibitory ratio of 40.78% at 10 μM. Compound 12 showed DPPH radical scavenging activity, with an EC50 of 16.21 µg/mL, compared to the positive control (ascorbic acid, EC50, 11.22 µg/mL). Furthermore, compound 4 exhibited cytotoxicity against PC-3 and LNCaP with IC50 values of 18.69 and 31.62 µM, respectively.

Two new polyketide derivatives, penirubenones A and B (1 and 2), and two naturally rare amino-bis-tetrahydrofuran derivatives, penirubenamides A and B (3 and 4), together with nine known compounds (5–13) were isolated from the marine-derived fungus Penicillium rubens BTBU20213035. The structures were identified by HRESIMS and 1D and 2D NMR analyses, and their absolute configurations were determined by a comparison of experimental and calculated electronic circular dichroism (ECD) spectroscopy and 13C NMR data. We found that 6 exhibited antibacterial activity against Staphylococcus aureus, with an MIC value of 3.125 μg/mL, and 1 and 2 showed synergistic antifungal activity against Candida albicans at 12.5 and 50 μg/mL with 0.0625 μg/mL rapamycin.

Streptomyces sp. N11-50 was isolated from deep-sea water and found to produce diketopiperazine (DKP) compounds such as albonoursin and cyclo(Phe-Leu). This study aimed to reveal the potential to synthesize diverse nonribosomal peptide and polyketide compounds as the other secondary metabolites different from DKP after clarifying the taxonomic position. Strain N11-50 was identified as Streptomyces albus, as it showed 100% 16S rRNA gene sequence similarities and 95.5% DNA–DNA relatedness to S. albus NBRC 13014T. We annotated the nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) gene clusters in the genome. Consequently, five NRPS, one hybrid PKS/NRPS, five type-I PKS and one type-II PKS gene clusters were observed, of which we predicted the products through bioinformatic analysis. These gene clusters were well conserved in already whole-genome sequence (WGS)-published strains belonging to S. albus. On the other hand, our taxonogenomic analysis revealed that three WGS-published S. albus strains were not S. albus. Two of the three should be classified as Streptomyces albidoflavus, and the remaining one was likely a new genomospecies. After reclassifying these appropriately, we demonstrated species-specific profiles of the NRPS and PKS gene clusters with little strain-level diversities.

Streptomyces justiciae WPN32 is an endophytic actinobacterium isolated from the rhizosphere of turmeric field soil at the Botanical Garden of Suranaree University of Technology (Nakhon Ratchasima Province, Thailand). Here we present the draft genome sequence of S. justiciae WPN32. It was sequenced on the Illumina NextSeq 550 sequencer. The draft genome consisted of 123 contigs with a total size of 9,832,147 base pairs, an N50 of 237,572 base pairs and a GC content of 70.87%. The dDDH between WPN32 and Streptomyces justiciae 3R004T was 80.1%, identifying the strain as Streptomyces justiciae. The data presented here may aid microbial taxonomy, comparative genomics and identification of gene clusters associated with the synthesis of bioactive compounds. The draft genome sequence data has been deposited at NCBI under Bioproject accession number PRJNA680432.

Background: Endophytic fungi have proven to be a rich source of novel natural products with a wide-array of biological activities and higher levels of structural diversity. Results: Chemical investigation on the liquid- and solid-state fermented products of Chaetomium globosum Km1226 isolated from the littoral medicinal herb Atriplex maximowicziana Makino resulted in the isolation of compounds 1–14. Their structures were determined by spectroscopic analysis as three previously undescribed C13-polyketides, namely aureonitol C (1), mollipilins G (2), and H (3), along with eleven known compounds 4–14. Among these, mollipilin A (5) exhibited significant nitric oxide production inhibitory activity in LPS-induced BV-2 microglial cells with an IC50 value of 0.7 ± 0.1 µM, and chaetoglobosin D (10) displayed potent anti-angiogenesis property in human endothelial progenitor cells (EPCs) with an IC50 value of 0.8 ± 0.3 µM. Conclusions: Three previously unreported compounds 1–3 were isolated and identified. Mollipilin A (5) and chaetoglobosin D (10) could possibly be developed as anti-inflammatory and anti-angiogenic lead drugs, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The urgent need for new antimicrobials arises from antimicrobial resistance. Actinobacteria, especially Streptomyces genus, are responsible for production of numerous clinical antibiotics and anticancer agents. Genome mining reveals the biosynthetic gene clusters (BGCs) related to secondary metabolites and the genetic potential of a strain to produce natural products. However, this potential may not be expressed under laboratory conditions. In the present study, the Antarctic bacterium was taxonomically affiliated as Streptomyces albidoflavus ANT_B131 (CBMAI 1855). The crude extracts showed antimicrobial activity against both fungi, Gram-positive and Gram-negative bacteria and antiproliferative activity against five human tumor cell lines. Whole-genome sequencing reveals a genome size of 6.96 Mb, and the genome mining identified 24 BGCs, representing 13.3% of the genome. The use of three culture media and three extraction methods reveals the expression and recovery of 20.8% of the BGCs. The natural products identified included compounds, such as surugamide A, surugamide D, desferrioxamine B + Al, desferrioxamine E, and ectoine. This study reveals the potential of S. albidoflavus ANT_B131 as a natural product producer. Yet, the diversity of culture media and extraction methods could enhance the BGCs expression and recovery of natural products, and could be a strategy to intensify the BGC expression of natural products. [ABSTRACT FROM AUTHOR]

DHA is a marine PUFA of commercial value, given its multiple health benefits. The worldwide emerging shortage in DHA supply has increased interest in microbial cell factories that can provide the compound de novo. In this regard, the present work aimed to improve DHA production in the oleaginous yeast strain Y. lipolytica Af4, which synthetized the PUFA via a heterologous myxobacterial polyketide synthase (PKS)-like gene cluster. As starting point, we used transcriptomics, metabolomics, and 13C-based metabolic pathway profiling to study the cellular dynamics of Y. lipolytica Af4. The shift from the growth to the stationary DHA-production phase was associated with fundamental changes in carbon core metabolism, including a strong upregulation of the PUFA gene cluster, as well as an increase in citrate and fatty acid degradation. At the same time, the intracellular levels of the two DHA precursors acetyl-CoA and malonyl-CoA dropped by up to 98% into the picomolar range. Interestingly, the degradation pathways for the ketogenic amino acids l -lysine, l -leucine, and l -isoleucine were transcriptionally activated, presumably to provide extra acetyl-CoA. Supplementation with small amounts of these amino acids at the beginning of the DHA production phase beneficially increased the intracellular CoA-ester pools and boosted the DHA titer by almost 40%. Isotopic 13C-tracer studies revealed that the supplements were efficiently directed toward intracellular CoA-esters and DHA. Hereby, l -lysine was found to be most efficient, as it enabled long-term activation, due to storage within the vacuole and continuous breakdown. The novel strategy enabled DHA production in Y. lipolytica at the gram scale for the first time. DHA was produced at a high selectivity (27% of total fatty acids) and free of the structurally similar PUFA DPA, which facilitates purification for high-value medical applications that require API-grade DHA. The assembled multi-omics picture of the central metabolism of Y. lipolytica provides valuable insights into this important yeast. Beyond our work, the enhanced catabolism of ketogenic amino acids seems promising for the overproduction of other compounds in Y. lipolytica , whose synthesis is limited by the availability of CoA ester precursors. • Multi-omics insights into the DHA-producer Yarrowia lipolytica Af4. • DHA production is limited by CoA-precursor availability. • Enhanced ketogenic amino acid catabolism boosts DHA production. • Lysine-supplementation provides DHA at the gram scale with high selectivity. [ABSTRACT FROM AUTHOR]

Polyketides and nonribosomal peptides are major secondary metabolites in members of the genus Streptomyces. Streptomyces cellostaticus is a validly recognized species and the type strain produces cellostatin. However, little is known about whether it has the potential to produce diverse polyketides and nonribosomal peptides. Here, we sequenced the whole genome of S. cellostaticus NBRC 12849T and surveyed polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene clusters in the genome. The genome encoded 12 PKS, one NRPS and eight hybrid PKS/NRPS gene clusters. Among the 21 gene clusters, products of 10 gene clusters were annotated to be an annimycin congener, fuelimycins, lankamycin, streptovaricin, spore pigment, flaviolin, foxicin, blasticidin, lankacidin and an incarnatapeptine congener via our bioinformatic analysis. Although the other clusters were orphan and their products were unknown, five of them were predicted to be compounds derived from two independent diketides, a tridecaketide, a triketide and a tetraketide with a cysteine residue, respectively. These results suggest that S. cellostaticus is a source of diverse polyketides and hybrid polyketide/nonribosomal peptides, including unknown and new secondary metabolites. [ABSTRACT FROM AUTHOR]

Five new polyketides, including two chromones (1–2), two phenyl derivatives (4–5), and a tandyukusin derivative (6), along with five known polyketides (3 and 7–10) were isolated from mangrove endophytic fungus Trichoderma lentiforme ML-P8-2. The planar structures of compounds were elucidated via detailed 1D, 2D NMR, and HR-ESI-MS analysis. ECD spectra, optical rotation values calculation, and alkali hydrolysis were applied in the determination of the absolute configuration of the new compounds. In bioassays, 6 and 9 exhibited promising antifungal activities against Penicillium italicum, with an MIC value of 6.25 μM for both compounds. Moreover, 3 displayed moderate AChE inhibitory activity with an IC50 value of 20.6 ± 0.3 μM. [ABSTRACT FROM AUTHOR]

Aromatic polyketide and phenylpropanoid derivatives are a large class of natural products produced by bacteria, fungi, and plants. The O -methylation is a unique decoration that can increase structural diversity of aromatic compounds and improve their pharmacological properties, but the substrate specificity of O -methyltransferase hinders the discovery of more natural products with O -methylation through biosynthesis. Here, we reported that the O -methyltransferase AurJ from plant pathogenic fungus Fusarium graminearum could methylate a broad range of natural substrates of monocyclic, bicyclic, and tricyclic aromatic precursors, exhibiting excellent substrate tolerance. This finding will partly change our stereotype about the specificity of traditional methyltransferases, and urge us to mine more O-methyltransferases with good substrate tolerance and discover more methylated natural products for drug discovery and development through directed evolution and combinatorial biosynthesis. [Display omitted] • O -methyltransferase AurJ from Fusarium Graminearum could methylate atrochrysone from plants or fungi in vivo and in vitro. • Unlike common methyltransferases, AurJ could methylate a broad range of substrates, showing excellent substrate tolerance. • AurJ exhibited good enzymatic activities on substrates atrochrysone and emodin, and their kinetic parameters were determined. [ABSTRACT FROM AUTHOR]

An environmentally sustainable world can be realized by using microorganisms to produce value-added materials from renewable biomass. Triacetic acid lactone (TAL) is a high-value-added compound that is used as a precursor of various organic compounds such as food additives and pharmaceuticals. In this study, we used metabolic engineering to produce TAL from glucose using an oleaginous yeast Yarrowia lipolytica. We first introduced TAL-producing gene 2-pyrone synthase into Y. lipolytica , which enabled TAL production. Next, we increased TAL production by engineering acetyl-CoA and malonyl-CoA biosynthesis pathways by redirecting carbon flux to glycolysis. Finally, we optimized the carbon and nitrogen ratios in the medium, culminating in the production of 4078 mg/L TAL. The strategy presented in this study had the potential to improve the titer and yield of polyketide biosynthesis. [ABSTRACT FROM AUTHOR]

Biofouling is the assemblage of undesirable biological materials and macro-organisms (barnacles, mussels, etc.) on submerged surfaces, which has unfavorable impacts on the economy and maritime environments. Recently, research efforts have focused on isolating natural, eco-friendly antifouling agents to counteract the toxicities of synthetic antifouling agents. Marine actinomycetes produce a multitude of active metabolites, some of which acquire antifouling properties. These antifouling compounds have chemical structures that fall under the terpenoids, polyketides, furanones, and alkaloids chemical groups. These compounds demonstrate eminent antimicrobial vigor associated with antiquorum sensing and antibiofilm potentialities against both Gram-positive and -negative bacteria. They have also constrained larval settlements and the acetylcholinesterase enzyme, suggesting a strong anti-macrofouling activity. Despite their promising in vitro and in vivo biological activities, scaled-up production of natural antifouling agents retrieved from marine actinomycetes remains inapplicable and challenging. This might be attributed to their relatively low yield, the unreliability of in vitro tests, and the need for optimization before scaled-up manufacturing. This review will focus on some of the most recent marine actinomycete-derived antifouling agents, featuring their biological activities and chemical varieties after providing a quick overview of the disadvantages of fouling and commercially available synthetic antifouling agents. It will also offer different prospects of optimizations and analysis to scale up their industrial manufacturing for potential usage as antifouling coatings and antimicrobial and therapeutic agents. [ABSTRACT FROM AUTHOR]