Discovery of a Chimeric Polyketide Family as Cancer Immunogenic Chemotherapeutic Leads

Discovery of cancer immunogenic chemotherapeutics represents an emerging, highly promising direction for cancer treatment that uses a chemical drug to achieve the efficacy of both chemotherapy and immunotherapy. Herein, we report a high-throughput screening platform and the subsequent discovery of a new class of cancer immunogenic chemotherapeutic leads. Our platform integrates informatics-based activity metabolomics for the rapid identification of microbial natural products with both novel structures and potent activities. Additionally, we demonstrate the use of microcrystal electron diffraction (MicroED) for direct structure elucidation of lead compounds from partially purified mixtures. Using this strategy to screen geographically and phylogenetically diverse microbial metabolites against pseudomyxoma peritonei, a rare and severe cancer, we discovered a new class of leads, aspercyclicins. The aspercyclicins feature an unprecedented tightly packed polycyclic polyketide scaffold that comprises continuous fused, bridged, and spiro rings. The biogenesis of aspercyclicins involves two distinct biosynthetic pathways, leading to formation of chimeric compounds that cannot be predicted by bottom-up approaches mining natural product biosynthetic genes. With comparable potency to some clinically used anticancer drugs, aspercyclicins are active against multiple cancer cell types by inducing immunogenic cell death (ICD), including the release of damage-associated molecular patterns and subsequent phagocytosis of cancer cells. The broad-spectrum ICD-inducing activity of aspercyclicins, combined with their low toxicity to normal cells, represents a new class of potential cancer immunogenic chemotherapeutics and, particularly, the first drug lead for pseudomyxoma peritonei treatment.

Discovery of A Chimeric Polyketide Family as Cancer Immunogenic Chemotherapeutic Leads

Discovery of cancer immunogenic chemotherapeutics represents an emerging, highly promising direction for cancer treatment that uses a chemical drug to achieve the efficacy of both chemotherapy and immunotherapy. Herein we report a high-throughput screening platform and the subsequent discovery of a new class of cancer immunogenic chemotherapeutic leads. Our platform integrates informatics-based activity metabolomics for rapid identification of microbial natural products with both novel structures and potent activities. Additionally, we demonstrate the use of microcrystal electron diffraction (MicroED) for direct structure elucidation of the lead compounds from partially purified mixtures. Using this strategy to screen geographically and phylogenetically diverse microbial metabolites against pseudomyxoma peritonei, a rare and severe cancer, we discovered a new class of leads, aspercyclicins. The aspercyclicins feature an unprecedented tightly packed polycyclic polyketide scaffold that comprises continuous fused, bridged, and spiro rings. The biogenesis of aspercyclicins involves two distinct biosynthetic pathways, leading to formation of chimeric compounds that cannot be predicted by bottom-up approaches mining natural products biosynthetic genes. With comparable potency to some clinically used anticancer drugs, aspercyclicins are active against multiple cancer cell types by inducing immunogenic cell death (ICD), including the release of damage-associated molecular patterns and subsequent phagocytosis of cancer cells. The broad-spectrum ICD-inducing activity of aspercyclicins, combined with their low toxicity to normal cells, represents a new class of potential cancer immunogenic chemotherapeutics and particularly the first drug lead for pseudomyxoma peritonei treatment.

Labelling studies in the biosynthesis of polyketides and non-ribosomal peptides

Covering: 2015 to 2022In this review, we discuss the recent advances in the use of isotopically labelled compounds to investigate the biosynthesis of polyketides, non-ribosomally synthesised peptides, and their hybrids. Also, we highlight the use of isotopes in the elucidation of their structures and investigation of enzyme mechanisms. The biosynthetic pathways of selected examples are presented in detail to reveal the principles of the discussed labelling experiments. The presented examples demonstrate that the application of isotopically labelled compounds is still the state of the art and can provide valuable information for the biosynthesis of natural products.

Spatial Genomic Resource Reveals Molecular Insights into Key Bioactive-Metabolite Biosynthesis in Endangered Angelica glauca Edgew

Angelica glauca Edgew, which is an endangered medicinal and aromatic herb, is a rich source of numerous industrially important bioactive metabolites, including terpenoids, phenolics, and phthalides. Nevertheless, genomic interventions for the sustainable utilization and restoration of its genetic resources are greatly offset due to the scarcity of the genomic resources and key regulators of the underlying specialized metabolism. To unravel the global atlas of the specialized metabolism, the first spatial transcriptome sequencing of the leaf, stem, and root generated 109 million high-quality paired-end reads, assembled de novo into 81,162 unigenes, which exhibit a 61.53% significant homology with the six public protein databases. The organ-specific clustering grouped 1136 differentially expressed unigenes into four subclusters differentially enriched in the leaf, stem, and root tissues. The prediction of the transcriptional-interactome network by integrating enriched gene ontology (GO) and the KEGG metabolic pathways identified the key regulatory unigenes that correspond to terpenoid, flavonoid, and carotenoid biosynthesis in the leaf tissue, followed by the stem and root tissues. Furthermore, the stem and root-specific significant enrichments of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), and caffeic acid 3-O-methyltransferase (COMT) indicate that phenylalanine mediated the ferulic acid biosynthesis in the stem and root. However, the root-specific expressions of NADPH-dependent alkenal/one oxidoreductase (NADPH-AOR), S-adenosyl-L-methionine-dependent methyltransferases (SDMs), polyketide cyclase (PKC), and CYP72A15 suggest the “root” as the primary site of phthalide biosynthesis. Additionally, the GC-MS and UPLC analyses corresponded to the organ-specific gene expressions, with higher contents of limonene and phthalide compounds in the roots, while there was a higher accumulation of ferulic acid in the stem, followed by in the root and leaf tissues. The first comprehensive genomic resource with an array of candidate genes of the key metabolic pathways can be potentially utilized for the targeted upscaling of aromatic and pharmaceutically important bioactive metabolites. This will also expedite genomic-assisted conservation and breeding strategies for the revival of the endangered A. glauca.

Barrettides: A Peptide Family Specifically Produced by the Deep-Sea Sponge Geodia barretti

Natural product discovery by isolation and structure elucidation is a laborious task often requiring ample quantities of biological starting material and frequently resulting in the rediscovery of previously known compounds. However, peptides are a compound class amenable to an alternative genomic, transcriptomic, and in silico discovery route by similarity searches of known peptide sequences against sequencing data. Based on the sequences of barrettides A and B, we identified five new barrettide sequences (barrettides C-G) predicted from the North Atlantic deep-sea demosponge Geodia barretti (Geodiidae). We synthesized, folded, and investigated one of the newly described barrettides, barrettide C (NVVPCFCVEDETSGAKTCIPDNCDASRGTNP, disulfide connectivity I-IV, II-III). Co-elution experiments of synthetic and sponge-derived barrettide C confirmed its native conformation. NMR spectroscopy and the anti-biofouling activity on larval settlement of the bay barnacle Amphibalanus improvisus (IC50 0.64 μM) show that barrettide C is highly similar to barrettides A and B in both structure and function. Several lines of evidence suggest that barrettides are produced by the sponge itself and not one of its microbial symbionts.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Cytotoxic, anti-biofilm and antimicrobial polyketides from the plant associated fungus Chaetosphaeronema achilleae

From extracts of the plant associated fungus Chaetosphaeronema achilleae collected in Iran, a previously unreported isoindolinone named chaetosisoindolinone (1) and a previously undescribed indanone named chaetosindanone (2) were isolated in addition to five known metabolites, 2-(2-acetyl-3,5-dihydroxyphenyl) acetic acid (3), vulculic acid (4), 2-(2-acetyl-3-hydroxy-5-methoxyphenyl)acetic acid (5), curvulin (6), and curvulol (7). Their structures were elucidated on the basis of extensive spectroscopic analysis and high-resolution mass spectrometry. The isolated compounds were tested for their antimicrobial, anti-biofilm, and nematicidal activities. Compound 2 exhibited cytotoxicity against the human breast adenocarcinoma MCF-7 cells with an IC₅₀ value of 1.5 μg/mL. Furthermore, compounds 4 and 7 almost completely inhibited biofilm formation in Staphylococcus aureus at 256 μg/mL. Weak antimicrobial activities were also observed for some of the isolated compounds against Mucor hiemalis, Rhodoturula glutinis, Chromobacterium violaceum, and Staphylococcus aureus.

New Aromatic Bisabolane Derivatives with Lipid-Reducing Activity from the Marine Sponge Myrmekioderma sp

The previously reported 1-(2,4-dihydroxy-5-methylphenyl)ethan-1-one (1), (1’Z)-2-(1’,5’-dimethylhexa-1’,4’-dieny1)-5-methylbenzene-1,4-diol (2), and 1,8-epoxy-1(6),2,4,7,10-bisaborapentaen-4-ol (5) together with four new structures of aromatic bisabolane-related compounds (3, 4, 6, 7) were isolated from the marine sponge Myrmekioderma sp. Compounds 1, 2, and 5 were identified based on spectral data available in the literature. The structures of the four new compounds were experimentally established by 1D and 2D-NMR and (−)-HRESIMS spectral analysis. Cytotoxic and lipid-reducing activities of the isolated compounds were evaluated. None of the isolated compounds were active against the tested cancer cell lines; however, lipid-reducing activity was found for compounds 2–5 and 7 in the zebrafish Nile red fat metabolism assay. This class of compounds should be further explored for their suitability as possible agents for the treatment of lipid metabolic disorders and obesity.

Hot off the Press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as niduterpenoid A from Aspergillus nidulans.