Disulfide bridge-targeted metabolome mining unravels an antiparkinsonian peptide.

Peptides are a particular molecule class with inherent attributes of some small-molecule drugs and macromolecular biologics, thereby inspiring continuous searches for peptides with therapeutic and/or agrochemical potentials. However, the success rate is decreasing, presumably because many interesting but less-abundant peptides are so scarce or labile that they are likely 'overlooked' during the characterization effort. Here, we present the biochemical characterization and druggability improvement of an unprecedented minor fungal RiPP (ribosomally synthesized and post-translationally modified peptide), named acalitide, by taking the relevant advantages of metabolomics approach and disulfide-bridged substructure which is more frequently imprinted in the marketed peptide drug molecules. Acalitide is biosynthetically unique in the macrotricyclization via two disulfide bridges and a protease (AcaB)-catalyzed lactamization of AcaA, an unprecedented precursor peptide. Such a biosynthetic logic was successfully re-edited for its sample supply renewal to facilitate the identification of the in vitro and in vivo antiparkinsonian efficacy of acalitide which was further confirmed safe and rendered brain-targetable by the liposome encapsulation strategy. Taken together, the work updates the mining strategy and biosynthetic complexity of RiPPs to unravel an antiparkinsonian drug candidate valuable for combating Parkinson's disease that is globally prevailing in an alarming manner.

Genome Mining and Heterologous Expression Guided the Discovery of Antimicrobial Naphthocyclinones from Streptomyces eurocidicus CGMCC 4.1086.

A type II polyketide synthase biosynthetic gene cluster (nap) was identified in Streptomyces eurocidicus CGMCC 4.1086 via genome mining. The heterologous expression of the cryptic nap gene cluster in Streptomyces albus J1074 generated dimerized aromatic polyketide naphthocyclinones (1-3), whose structures were determined via extensive analysis using nuclear magnetic resonance and high-resolution electrospray ionization mass spectroscopy. The biological pathway of naphthocyclinone synthesis was revealed via in vivo gene deletion, in vitro biochemical reactions, and comparative genomics. Remarkably, 3 played a crucial role in inhibiting Phytophthora capsici and Phytophthora sojae, with EC50 values of 6.1 and 20.2 µg/mL, respectively. Furthermore, 3 exhibited a potent protective effect against P. capsici and P. sojae in greenhouse tests.

Seven drimane-type sesquiterpenoids from an earwig-associated Aspergillus sp.

Drimane-type sesquiterpenoids are widely distributed in fungi. From the ethyl acetate extract of the earwig-derived Aspergillus sp. NF2396, seven new drimane-type sesquiterpenoids, named drimanenoids A-G (1-7), were isolated. Their structures were elucidated by diverse spectroscopic analysis including high-resolution ESI-MS, one- and two-dimensional NMR spectroscopy. Drimanenoids A-F (1-6) are new members of drimane-type sesquiterpenoid esterified with unsaturated fatty acid side chain at C-6. Drimanenoids C (3), D (4) and F (6) showed antibacterial activity against five types of bacteria with different inhibition diameters. Drimanenoid D (4) exhibited moderate cytotoxicity against human myelogenous leukemia cell line K562 with an IC50 value of 12.88 ± 0.11 µmol·L-1.

New metabolites from Streptomyces pseudovenezuelae NA07424 and their potential activity of inducing resistance in plants against Phytophthora capsici.

BACKGROUND: The lack of novel fungicide and appearance of resistance are the most emergent problems in the control of Phytophthora diseases. Plant immunity elicitors that induce systemic resistance in plants are regarded as the new strategy for plant disease control. Streptomyces can produce a variety of bioactive natural products, which are important resources for lead compounds of plant immunity elicitors. RESULTS: A novel peptidendrocin C (1) together with the known analog peptidendrocin B (2) were isolated from Streptomyces pseudovenezuelae NA07424. Their structures were confirmed by spectroscopic data and Marfey's reaction. In bioactive assays, compound 1 played an important role in inducing systemic resistance of Nicotiana benthamiana against Phytophthora capsici growth, with a 90.5% inhibition ratio at 400 µg/mL, while compound 2 showed moderate activity, inhibiting P. capsici growth by a 50.8% decrease at 400 µg/mL. Simultaneously, two compounds promoted enhanced expression of the PR1 gene and callose accumulation in N. benthamiana and Arabidopsis thaliana. In this paper, we also provide the first insights into their biosynthesis by confirming their biosynthesis gene cluster and related functional genes. CONCLUSION: Our findings show that 1 and 2 have the potential to be used as lead compounds for development of new plant immunity elicitors to control Phytophthora diseases. The study of the biosynthesis pathway lays the groundwork for further application of the bioactive natural products. © 2022 Society of Chemical Industry.

New antibacterial depsidones from an ant-derived fungus Spiromastix sp. MY-1.

Six new (1-6) and seven known depsidones (7-13) were isolated from the culture of an ant (Monomorium chinensis)-derived fungus Spiromastix sp. MY-1. Their structures were elucidated by extensive spectroscopic analysis including high resolution MS, 1D and 2D NMR data. The new bromide depsidones were obtained through supplementing potassium bromide in the fermentation medium of Spiromastix sp. MY-1. All isolated compounds showed various bioactivities against the tested phytopathogenic bacteria. Particularly, new bromide compound 4, named spiromastixone S, exhibited the strongest activity against Xanthomonas oryzae pv. oryzae with a MIC value of 5.2 µmol·-1.

Alternatones A and B, two polyketides possessing novel skeletons from entophyte Alternaria alternate L-10.

On our ongoing searching for bioactive natural products derived from entophytes, two polyketides possessing novel skeletons, alternatones A-B (1-2), were identified from the culture of Alternaria alternate L-10. Their structures were established by a combination of spectroscopic and single-crystal X-ray diffraction with Cu Ka radiation. Alternatone A (1) exhibited cytotoxic activity against human hepatoma carcinoma HepG-2 cell line. The putative biosynthetic pathways for compounds 1-2 were also proposed.

Zhaoshumycins A and B, Two Unprecedented Antimycin-Type Depsipeptides Produced by the Marine-Derived Streptomyces sp. ITBB-ZKa6.

Marine actinomycetes are prolific chemical sources of complex and novel natural products, providing an excellent chance for new drug discovery. The chemical investigation of the marine-derived Streptomyces sp. ITBB-ZKa6, from Zhaoshu island, Hainan, led to the discovery of two unique antimycin-type depsipeptides, zhaoshumycins A (1) and B (2), along with the isolation of the four known neoantimycins A (3), F (4), D (5), and E (6). The structures of the new compounds 1 and 2 were elucidated on the basis of the analysis of diverse spectroscopic data and biogenetic consideration. Zhaoshumycins A (1) and B (2) represent a new class of depsipeptides, featuring two neoantimycin monomers (only neoantimycin D or neoantimycins D and E) linked to a 1,4-disubstituted benzene ring via an imino group. Initial toxicity tests of 1-6 in MCF7 human breast cancer cells revealed that compounds 5 and 6 possess weak cytotoxic activity. Further structure-activity relationship analysis suggested the importance of the NH2 group at C-34 in 5 and 6 for cytotoxicity in MCF7 cells.

Study on the secondary metabolites of grasshopper-derived fungi Arthrinium sp. NF2410.

Two new 2-carboxymethyl-3-hexyl-maleic anhydride derivatives, arthrianhydride A (1) and B (2), along with three known compounds 3-5, were isolated from the fermentation broth of a grasshopper-associated fungus Arthrinium sp. NF2410. The structures of new compounds 1 and 2 were determined based on the analysis of the HR-ESI-MS and NMR spectroscopic data. Furthermore, compounds 1 and 2 were evaluated on inhibitory activity against the enzyme SHP2 and both of them showed moderate inhibitory activity against SHP2.

Shoreanol A and B, unprecedented oligostilbenoids from the twigs of Shorea obtusa Wall.

Chemical investigation of the twigs extract of tropical dipterocarpaceous plant Shorea obtusa Wall led to the isolation of two previously undescribed oligostilbenoids, including a structurally unusual resveratrol aneuploid named shoreanol A (1) and a new resveratrol trimer derivative named shoreanol B (2). Their structures and relative configurations were determined by comprehensive spectroscopic analysis and comparison with previously reported compound. Shoreanol A (1) was identified as a rare natural resveratrol aneuploid possessing a novel carbon skeleton through condensation of three resveratrol monomer and one benzyl moiety, which is the first example in the Dipterocarpaceae. While shoreanol B (2) was characterized to be the first example of stilbene trimer bearing an epoxy group in the genus Shorea.

Libertellenone M, a diterpene derived from an endophytic fungus Phomopsis sp. S12, protects against DSS-induced colitis via inhibiting both nuclear translocation of NF-κB and NLRP3 inflammasome activation.

NLRP3 inflammasome may serve as a potential target for the development of novel therapeutics for inflammatory bowel diseases. In this study, we found that Libertellenone M (Lib M), a secondary metabolite from the endophytic fungus Phomopsis sp. S12, has anti-inflammatory potential both in vitro and in vivo. Lib M selectively inhibited the expression of proinflammatory cytokine IL-1ß and IL-18 in LPS-activated macrophages. The cleavage of pro-caspase 1 was remarkably reduced by Lib M in macrophages stimulated with three NLRP3 inflammasome activators. Administering Lib M attenuated dextran sulfate sodium-induced experimental acute colitis in mice and significantly reduced the production of these cytokines and cleaved caspase 1 in colon tissues. Apart from inhibition of NLRP3 inflammasome assembly, Lib M also suppressed NF-κB nuclear translocation in macrophages. Taken together, these findings suggest that Lib M-mediated inhibition of NLRP3 inflammasome activation could protect against colitis-like inflammatory diseases, and that this compound derived from a plant-associated fungus might inspire the exploration of novel immunosuppressive agents.

Neocucurbitacin D, a novel lactone-type norcucurbitacin as xanthine oxidase inhibitor from Herpetospermum pedunculosum.

A novel lactone-type norcucurbitacin, designated as neocucurbitacin D (1), together with five known cucurbitane triterpenes were isolated from traditional Tibetan medicine "Se Ji Mei Duo", which is the seed of Herpetospermum pedunculosum (Ser.) C.B. Clarke. The structure of neocucurbitacin D was elucidated by spectroscopic analysis, including 2D NMR and X-ray techniques. Compounds 1-6 were screened for their xanthine oxidase (XOD) inhibitory activity. Compound 1, 2 and 4 exhibited significant XOD inhibition with IC50 values ranging from 10.16 to 18.41 µM. The absolute stereochemistry and XOD inhibitiory activity of lactone-type norcucurbitacins was reported firstly.

Bioactive phenazines from an earwig-associated Streptomyces sp.

Three new phenazine-type compounds, named phenazines SA-SC (1-3), together with four new natural products (4-7), were isolated from the fermentation broth of an earwig-associated Streptomyces sp. NA04227. The structures of these compounds were determined by extensive analyses of NMR, high resolution mass spectroscopic data, as well as single-crystal X-ray diffraction measurement. Sequencing and analysis of the genome data allowed us to identify the gene cluster (spz) and propose a biosynthetic pathway for these phenazine-type compounds. Additionally, compounds 1-5 exhibited moderate inhibitory activity against acetylcholinesterase (AChE), and compound 3 showed antimicrobial activities against Micrococcus luteus.

Dalestones A and B, two anti-inflammatory cyclopentenones from Daldinia eschscholzii with an edited strong promoter for the global regulator LaeA-like gene.

Replacement of the native promoter of theglobal regulator LaeA-like gene of Daldinia eschscholzii by a strong gpdA promoter led to the generation of two novel cyclopentenone metabolites, named dalestones A and B, whose structures were assigned by a combination of spectroscopic analysis, modified Mosher's reaction, and electronic circular dichroism (ECD). Dalestones A and B inhibit the gene expression of TNF-α and IL-6 in LPS-induced RAW264.7 macrophages.

Cytotoxic Trichothecene Macrolides Produced by the Endophytic Myrothecium roridum.

Six new macrolides named myrothecines D-G (1-4), 16-hydroxymytoxin B (5), and 14'-dehydrovertisporin (6), including four 10,13-cyclotrichothecane derivatives, in addition to 12 known compounds (7-18), were isolated from three endophytic Myrothecium roridum, IFB-E008, IFB-E009, and IFB-E012. The isolated compounds were characterized by MS, NMR, CD, and single-crystal X-ray crystallography. The isolated macrolides exhibited an antiproliferation effect against chronic myeloid leukemia K562 and colorectal carcinoma SW1116 cell lines. Compounds 1-6 were cytotoxic, with IC50 values ranging between 56 nM and 16 µM. Since slight structural changes led to obvious activity differences, the CoMFA (comparative molecular field analysis) and CoMSIA (comparative molecular similarity indices analysis) methods were then used to explore the 3D QSAR (three-dimensional quantitative structure-activity relationship) of these macrolides. The result showed that the steric, electrostatic, hydrophobic, and H-bond acceptor factors were involved in their cytotoxicity and provided an in-depth understanding of the structure-activity relationships of these metabolites.

Knockdown long noncoding RNA nuclear paraspeckle assembly transcript 1 suppresses colorectal cancer through modulating miR-193a-3p/KRAS.

The nuclear paraspeckle assembly transcript 1 (abbreviated as NEAT1), a nuclear sufficient long noncoding RNA (abbreviated as lncRNA), has aroused a rising concern in recent years. As uncovered by reports, the increase in NEAT1 is related to the deteriorated prognosis of lung cancer, breast cancer, hepatocellular cancer, and colorectal cancer (abbreviated as CRC). Thus far, the mechanism of NEAT1 has not been elucidated by the existing researches. The impact of knockdown of both NEAT1 and its predicted downstream miR-193a-3p in CRC cells was examined here to delve into their interactions and mechanisms. Additionally, the target of miR-193a-3p, Kirsten rat sarcoma viral oncogene homolog (abbreviated as KRAS), was also predicted by bioinformatics algorithms. Small interfering RNA and antisense oligonucleotides that inhibit NEAT1, as well as overexpression or knockdown of miR-193a-3p, were adequately drawn upon to confirm that NEAT1 serves as a miR-193a-3p sponge or competing endogenous RNA, to impact miR-193a-3p's further functions, including modulating KRAS proteins, both in vitro and in vivo. Generally, lncRNA NEAT1/hsa-miR-193a-3p/KRAS axis was substantiated in CRC cells and could provide novel insight into both diagnostic and therapeutic advancement in CRC.

MicroRNA-181a promotes angiogenesis in colorectal cancer by targeting SRCIN1 to promote the SRC/VEGF signaling pathway.

Colorectal cancer (CRC) is a very common metastatic tumor with active angiogenesis that requires active angiogenesis. Recently, increased microRNA-181a-5p (miR-181a) expression was found to be significantly associated with liver metastasis and poor outcome in CRC patients. In this study, the role of miR-181a in tumor angiogenesis was further investigated. Capillary tube formation assays were used to demonstrate the ability of miR-181a to promote tumor angiogenesis. Bioinformatics analyses identified SRC kinase signaling inhibitor 1 (SRCIN1) as a potential target of miR-181a. Next, two CRC cell lines (HT29 and SW480) were used to clarify the function of miR-181a through SRCIN1 targeting. In addition, the biological effects of SRCIN1 inhibition by miR-181a were examined in vitro by quantitative RT-PCR, western blotting and enzyme-linked immunosorbent assay and in vivo by Matrigel plug angiogenesis assays and immunohistochemical staining. In clinical samples, Fluorescence in situ hybridization and immunofluorescence were performed to detect the relation between miR-181a and SRCIN1. In addition, SRCIN1 protein and miR-181a expression levels in CRC tissues were also measured by western blot and quantitative real-time polymerase chain reaction. MiR-181a markedly augmented the capability of CRC cells to advance tube formation in endothelial cells in vitro. The Matrigel plug assay showed that miR-181a promoted angiogenesis in vivo. In conclusion, miR-181a inhibited SRCIN1, which caused SRC to transform from an inactive status to an active conformation and to trigger vascular endothelial growth factor secretion, leading to increased angiogenesis. MiR-181a dysregulation contributes to angiogenesis in CRC, and downregulation of miR-181a represents a promising, novel strategy to achieve an efficient antiangiogenic response in anti-CRC therapy.

New Antibacterial Phenone Derivatives Asperphenone A-C from Mangrove-Derived Fungus Aspergillus sp. YHZ-1.

Marine fungi are a promising source of novel bioactive natural products with diverse structure. In our search for new bioactive natural products from marine fungi, three new phenone derivatives, asperphenone A-C (1-3), have been isolated from the ethyl acetate extract of the fermentation broth of the mangrove-derived fungus, Aspergillus sp. YHZ-1. The chemical structures of these natural products were elucidated on the basis of mass spectrometry, one- and two-dimensional NMR spectroscopic analysis and asperphenone A and B were confirmed by single-crystal X-ray crystallography. Compounds 1 and 2 exhibited weak antibacterial activity against four Gram-positive bacteria, Staphylococcus aureus CMCC(B) 26003, Streptococcus pyogenes ATCC19615, Bacillus subtilis CICC 10283 and Micrococcus luteus, with the MIC values higher than 32.0 µM.

Novel chaetospirolactone and orsellide F from an endophytic fungus Chaetomium sp.

Chaetospirolactone (1), a novel spiro-lactone bearing a rare 1-oxaspiro [4.4] non-7-ene-2,6-dione skeleton, and orsellide F (2), together with six known compounds (3-8), were isolated from an endophytic fungus Chaetomium sp. NF00754. Their structures were determined by interpretation of spectroscopic data. The absolute configurations of 1 and 2 were established by analysis of single X-ray crystallographic data and CD spectra. Compounds 3, 4, and 6 showed moderate acetylcholinesterase inhibitory activity with IC50 values of 7.34, 5.19, and 7.67 µM, respectively.

Strepchazolins A and B: Two New Alkaloids from a Marine Streptomyces chartreusis NA02069.

Two new alkaloids, strepchazolins A (1) and B (2), together with a previously reported compound, streptazolin (3), were isolated from a marine actinomycete, Streptomyces chartreusis NA02069, collected in the Coast of Hainan Island, China. The structures of new compounds were determined by extensive NMR, mass spectroscopic and X-ray crystallographic analysis, as well as modified Mosher's method. Compound 1 showed weak anti-Bacillus subtilis activity with the MIC value of 64.0 µM, and weak inhibitory activity against acetylcholinesterase (AChE) in vitro with IC50 value of 50.6 µM, while its diastereoisomer, Compound 2, is almost inactive.