Nucleobase-Coupled Xanthones with Anti-ROS Effects from Marine-Derived Fungus Aspergillus sydowii.

A MS/MS-based molecular networking approach compared to the Global Natural Product Social Molecular Networking library, in association with genomic annotation of natural product biosynthetic gene clusters within a marine-derived fungus, Aspergillus sydowii, identified a suite of xanthone metabolites. Chromatographic techniques applied to the cultured fungus led to the isolation of 11 xanthone-based alkaloids, dubbed sydoxanthones F-M. The structures of these alkaloids were elucidated using extensive spectroscopic data, including electronic circular dichroism and single-crystal X-ray diffraction data for configurational assignments. Among these analogues, sydoxanthones F-K exhibit structure features typical of nucleobase-coupled xanthones, with sydoxanthone H being an N-bonded xanthone dimer. Notably, (±)sydoxanthones F (1a/1b), (±)sydoxanthones H (3b/3a), and (±)sydoxanthones J (5b/5a) are enantiomeric pairs, while sydoxanthones G (2), I (4), and K (6) are stereoisomers of 1, 3, and 5, respectively. Furthermore, (+)sydoxanthone H (3a) demonstrated significant rescue of cell viability in H2O2-injuried SH-SY5Y cells by inhibiting reactive oxygen species production, suggesting its potential for neuroprotection.

New Diterpenes and Diterpene Glycosides with Antibacterial Activity from Soft Coral Lemnalia bournei.

Five new biflorane-type diterpenoids, biofloranates E-I (1-5), and two new bicyclic diterpene glycosides, lemnaboursides H-I (6-7), along with the known lemnabourside, were isolated from the South China Sea soft coral Lemnalia bournei. Their chemical structures and stereochemistry were determined based on extensive spectroscopic methods, including time-dependent density functional theory (TDDFT) ECD calculations, as well as a comparison of them with the reported values. The antibacterial activities of the isolated compounds were evaluated against five pathogenic bacteria, and all of these diterpenes and diterpene glycosides showed antibacterial activities against Staphylococcus aureus and Bacillus subtilis, with MICs ranging from 4 to 64 µg/mL. In addition, these compounds did not exhibit noticeable cytotoxicities on A549, Hela, and HepG2 cancer cell lines, at 20 µM.

Irpetones A and B, Anti-Osteoclastic Heptaketides from a Marine Mesophotic Zone Ircinia Sponge-Associated Fungus Irpex sp. NBUF088.

Chemical investigation of Irpex sp. NBUF088, associated with an Ircinia sp. sponge located at an 84 m deep mesophotic zone, led to the discovery of two new heptaketides, named irpetones A (1) and B (2). Their structures were identified by analysis of spectroscopic data and quantum-chemical calculations. Compound 1 exhibited inhibition against the receptor activator of NF-κB ligand-induced osteoclastogenesis in bone marrow monocytes with an IC50 of 6.3 ± 0.2 µM, causing no notable cytotoxicity. It was also determined that 1 inhibited the phosphorylation of ERK1/2-JNK1/2-p38 MAPKs and the nuclear translocation of NF-κB, consequently suppressing the activation of MAPK and NF-κB signaling pathways induced by the NF-κB ligand.

Biosynthesis of Epipyrone A Reveals a Highly Specific Membrane-Bound Fungal C-Glycosyltransferase for Pyrone Galactosylation.

Epipyrone A is a unique C-galactosylated 4-hydroxy-2-pyrone derivative with an antifungal potential from the fungus Epicoccum nigrum. We elucidated its biosynthesis via heterologous expression and characterized an unprecedented membrane-bound pyrone C-glycosyltransferase biochemically. Molecular docking and mutagenesis experiments suggested a possible mechanism for the heterocyclic C-glycosylation and the importance of a transmembrane helix for its catalysis. These results expand the repertoire of C-glycosyltransferases and provide new insights into the formation of C-glycosides in fungi.

Brominated Depsidones with Antibacterial Effects from a Deep-Sea-Derived Fungus Spiromastix sp.

Eleven new brominated depsidones, namely spiromastixones U-Z5 (1-11) along with five known analogues (12-16), were isolated from a deep-sea-derived fungus Spiromastix sp. through the addition of sodium bromide during fermentation. Their structures were elucidated by extensive analysis of the spectroscopic data including high-resolution MS and 1D and 2D NMR data. Compounds 6-10 and 16 exhibited significant inhibition against Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VRE) with MIC values ranging from 0.5 to 2.0 µM. Particularly, tribrominated 7 displayed the strongest activity against MRSA and VRE with a MIC of 0.5 and 1.0 µM, respectively, suggesting its potential for further development as a new antibacterial agent.

Targeted isolation of sorbicilinoids from a deep-sea derived fungus with anti-neuroinflammatory activities.

A chemical fingerprinting approach utilizing LC-MS/MS coupled with 2D NMR data was established to characterize the profile of sorbicilinoid-type metabolites from a deep-sea derived fungus Penicillium rubens F54. Targeted isolation of the cultured fungus resulted in the discovery of 11 undescribed sorbicilinoids namely sorbicillinolides A-K (1-11). Their structures were identified by extensive analyses of the spectroscopic data, including the calculation of electronic circular dichroism and optical rotation for configurational assignments. The cyclopentenone core of sorbicillinolides A-D is likely derived from sorbicillin/dihydrosorbicillin through a newly oxidative rearrangement. The stereoisomers of sorbicillinolides E-G incorporate a nitrogen unit, forming a unique hydroquinoline nucleus. Sorbicillinolides A and C exhibited significant anti-neuroinflammation in LPS-stimulated BV-2 macrophages, achieved by potent inhibition of NO and PGE2 production through the interruption of RNA transcription of iNOS, COX-2 and IL6 in the NF-κB signaling pathway. Further investigation identified COX-2 as a potential target of sorbicillinolide A. These findings suggest sorbicillinolide A as a potential lead for the development of a non-steroidal anti-neuroinflammatory agent.

Pestanoid A, a Rearranged Pimarane Diterpenoid Osteoclastogenesis Inhibitor from a Marine Mesophotic Zone Chalinidae Sponge-Associated Fungus, Pestalotiopsis sp. NBUF145.

One novel rearranged pimarane diterpenoid, pestanoid A (1), and two reported molecules, nodulisporenones A (2) and B (3), were discovered from Pestalotiopsis sp. NBUF145 fungus associated with a 62 m deep mesophotic ("twilight") zone Chalinidae sponge. The structures of 1-3 were identified by spectrometry, spectroscopy, quantum-chemical calculations, and X-ray crystallography. Compounds 1 and 2 inhibited bone marrow monocyte osteoclastogenesis in vitro with the IC50 values 4.2 ± 0.2 µM and 3.0 ± 0.4 µM, respectively, without observed cytotoxicity. Both 1 and 2 suppressed the receptor activator of NF-kB ligand-induced MAPK and NF-κB signaling by inhibiting the phosphorylation of ERK1/2-JNK1/2-p38 MAPKs and NF-κB nuclear translocation.

Indoloquinazoline alkaloids suppress angiogenesis and inhibit metastasis of melanoma cells.

Metastasis is the leading cause of cancer-related mortality, targeting angiogenesis emerges as a therapeutic strategy for the treatment of melanoma metastasis. Discovery of new antiangiogenic compounds with specific mechanism of action is still desired. In present study, a bioassay-guidance uncovers the EtOAc extract of a marine-derived fungus Aspergillus clavutus LZD32-24 with significant inhibitory activity against the angiogenesis in Tg (fli1a: EGFP) zebrafish model. Extensive chromatographic fractionation led to the isolation of 48 indoloquinazoline alkaloids, including 21 new analogues namely clavutoines A-U (1-21). Their structures were determined by the spectroscopic data, including the ECD, single crystal X-ray diffraction and quantum chemical calculation for the configurational assignments. Among the bioactive analogues, quinadoline B (QB) showed the most efficacy to suppress the zebrafish vascular outgrowth in zebrafish embryos. QB markedly inhibited the migration, invasion and tube formation with weak cytotoxicity in human umbilical vein endothelial cells (HUVECs). Investigation of the mode of action revealed QB suppressed the ROCK/MYPT1/MLC2/coffin and FAK /Src signaling pathways, and subsequently disrupted actin cytoskeletal organization. In addition, QB reduced the number of new vessels sprouting from the ex vivo chick chorioallantoic membrane (CAM), and inhibited the metastasis of B16F10 melanoma cells in lung of C57BL/6 mice through suppressing angiogenesis. These findings suggest that QB is a potential lead for the development of new antiangiogenic agent to inhibit melanoma metastasis.

Targeted Isolation of Dolabellane Diterpenoids from the Soft Coral Clavularia viridis Using Molecular Networking.

LC-MS/MS-based molecular networking annotation coupled 1H NMR detection allowed the depiction of the soft coral Clavularia viridis to produce a profile of dolabellane-type diterpenoids. Chromatographic separation of the EtOAc fraction resulted in the isolation of 12 undescribed dolabellane-type diterpenoids, namely, clavirolides J-U (1-12). Their structures were characterized by the extensive analysis of the spectroscopic data, including the calculated ECD and X-ray diffraction for the configurational assignments. Clavirolides J-K are characterized by a 1,11- and 5,9-fused tricyclic tetradecane scaffold fused with a α,ß-unsaturated-δ-lactone, and clavirolide L possesses a 1,11- and 3,5-fused tricyclic tetradecane scaffold, which extend the dolabellane-type scaffolds. Clavirolides L and G showed significant inhibition against HIV-1 without RT enzyme inhibition, providing additional non-nucleosides with different mechanisms from efavirenz.

Molecular networking-guided isolation of undescribed antifungal odoriferous sesquiterpenoids from a marine mesophotic zone sponge-associated Streptomyces sp. NBU3428.

Under the guidance of MS/MS-based molecular networking, eight odoriferous sesquiterpenes including two undescribed geosmin-type sesquiterpenoid degradations, odoripenoid A (1) and odoripenoid B (2), and two undescribed germacrane-type sesquiterpenoids, odoripenoid C (3) and odoripenoid (4), together with four known related compounds (5-8) were isolated from the EtOAc extract of the marine mesophotic zone sponge-associated Streptomyces sp. NBU3428. All chemical structures including absolute configurations of these compounds were elucidated by means of HRESIMS, NMR, ECD calculations and single-crystal X-ray diffraction experiments. Compounds 1 and 2 represent the rarely geosmin-related metabolites directly as natural products from actinomycetes. The isolated compounds (1-8) were assayed in a range of biological activities. Compounds 1 and 2 showed anti-Candida albicans activity with MIC values of 16 and 32 µg/mL, respectively, representing potential antifungal agents.

Bio-Active Products from Mangrove Ecosystems.

Mangrove communities represent the coastal habitats located in intertidal zones or brackish waters of tropical and subtropical coastal areas in over 118 countries [...].

Discovery of uncommon terpenoids from the South China Sea soft coral Sinularia scabra.

Sinulatones A and B, presented as the unusual carbon skeleton with bicyclo[4.5.0] system, two undescribed sesquiterpenoids, namely sinulalides A and B, along with eight known terpenoids, were isolated from the South China Sea soft coral Sinularia scabra. The structures and stereochemistry of these compounds were determined based on extensive spectroscopic data analyses, and computer-assisted methods, including the quantum mechanical-nuclear magnetic resonance (QM-NMR) and TDDFT-ECD calculations. In bioassay, sinulatones A and B showed inhibitory activity against osteoclast precursor cells, with IC50 values of 16.8 and 5.8 µM, respectively.

Briarane-type diterpenoids, the inhibitors of osteoclast formation by interrupting Keap1-Nrf2 interaction and activating Nrf2 pathway.

Chemoinformatic and bioassay-guided fractionation of a gorgonian coral Junceella juncea resulted in the isolation of 45 briarane-type diterpenoids, of which 16 new analogues were characterized. Their structures were identified by extensive analyses of the spectroscopic data. Most isolated briaranes showed significant inhibition against the receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast differentiation in bone marrow-derived macrophages cells (BMMs). Praelolide, one of the active analogues, significantly activates nuclear factor erythroid-2-related factor 2 (Nrf2) nucleus translocation, induces the expression of Nrf2-targeted genes, suppresses reactive oxygen species (ROS) production, abrogates the activation of downstream mitogen-activated protein kinase (MAPK)/nuclear factor-κB (NFκB) signaling, and subsequently attenuates osteoclast differentiation. Mechanically, praelolide interacts with Kelch-like ECH-associated protein 1 (Keap1) protein by non-covalent interaction to interrupt the interaction between Keap1 and Nrf2 and thereby to activate the Nrf2 signaling pathway. In addition, praelolide rescues the bone loss in prednisone-induced zebrafish. The present study provided praelolide as a new natural scaffold to remedy osteoclastogenic bone disease.

Acorane sesquiterpenes from the deep-sea derived Penicillium bilaiae fungus with anti-neuroinflammatory effects.

Acorane-type sesquiterpenes comprise a unique class of natural products with a range of pharmaceutical effects. Genome sequencing and gene annotation, along with qRT-PCR detection, demonstrate that the deep-sea derived Penicillium bilaiae F-28 fungus shows potential to produce acorane sesquiterpenes. Chromatographic manipulation resulted in the isolation of 20 acorane sesquiterpenes from the large-scale fermented fungal strain. Their structures were established by the interpretation of spectroscopic data, together with X-ray diffraction, chemical conversion, and ECD data for configurational assignments. A total of 18 new sesquiterpenes, namely, bilaiaeacorenols A-R (1-18), were identified. Bilaiaeacorenols A and B represent structurally unique tricyclic acoranes. Compound 18 exhibited efficient reduction against NO production in LPS-induced BV-2 macrophages in a dose-dependent manner, and it abolished LPS-induced NF-κB in the nucleus of BV-2 microglial cells. In addition, marked reductions of iNOS and COX-2 in protein and mRNA levels were observed. This study extends the chemical diversity of acorane-type sesquiterpenoids and suggests that compound 18 is a promising lead for anti-neuroinflammation.

Eremophilane-Type Sesquiterpenes from a Marine-Derived Fungus Penicillium Copticola with Antitumor and Neuroprotective Activities.

Chemical examination of a marine sponge-associated Penicillium copticola fungus resulted in the isolation of ten undescribed eremophilanes, namely copteremophilanes A-J (1-10), along with two new glycosides, 5-glycopenostatin F (11) and 5-glucopenostatin I (12). Their structures were determined by extensive spectroscopic data, in association with ECD data and chemical conversions for configurational assignments. Analogs 1, 2, and 10 represent a group of uncommon skeletons of eremophilanes with an aromatic ring and a methyl migration from C-5 to C-9, and analogs 11 and 12 are characteristic of a PKS scaffold bearing a glucose unit. The incorporation of a chlorinated phenylacetic unit in 3-9 is rarely found in nature. Analog 7 showed neuroprotective effect, whereas 8 exhibited selective inhibition against human non-small cell lung cancer cells (A549). This study enriched the chemical diversity of eremophilanes and extended their bioactivities to neuroprotection.

Concise Biosynthesis of Tropone-Containing Spiromaterpenes by a Sesquiterpene Cyclase and a Multifunctional P450 from a Deep-Sea-Derived Spiromastix sp. Fungus.

Spiromaterpenes are a group of rare tropone-containing sesquiterpenes with antineuroinflammatory activity. Herein, we elucidate their biosynthetic pathway in a deep-sea-derived Spiromastix sp. fungus by heterologous expression, biochemical characterization, and incubation experiments. The sesquiterpene cyclase SptA was first characterized to catalyze the production of guaia-1(5),6-diene, and a multifunctional cytochrome P450 catalyzed the tropone ring formation. These results provide important clues for the rational mining of bioactive guaiane-type sesquiterpenes and expand the repertoire of P450 activities to synthesize unique building blocks of natural products.

Equisetin Targets Intracellular Staphylococcus aureus through a Host Acting Strategy.

Mammalian cells act as reservoirs of internalized bacteria to circumvent extracellular antibacterial compounds, resulting in relapse and reinfection diseases. The intracellular persistence of Staphylococcus aureus renders most traditional antibiotics useless, due to their inadequate subcellular accumulation. To replenish our antibiotic arsenal, we found that a marine-derived compound, equisetin, efficiently eliminates intracellular S. aureus by potentiating the host autophagy and inducing mitochondrial-mediated ROS generation to clear the invading S. aureus. The remarkable anti-infection activity of equisetin was validated in a peritonitis-infected mouse model. The marine product equisetin utilizes a unique dual mechanism to modulate the host-pathogen interaction in the clearance of intracellular bacteria. Thus, equisetin is an inspiring host-acting candidate for overcoming intracellular pathogens.

Prenylated notoamide-type alkaloids isolated from the fungus Aspergillus sclerotiorum and their inhibition of NLRP3 inflammasome activation and antibacterial activities.

Notoamides are a family of prenylated indole alkaloids with unusual ring systems and possessing a range of significant pharmaceutical activities. Based on LC-MS/MS and genome orientations, ten undescribed notoamide-type alkaloids namely sclerotiamides I-R were isolated from a marine gorgonian-derived fungus Aspergillus sclerotiorum LZDX-33-4. Their structures were determined by extensive spectroscopic data, in association with ECD data and single-crystal X-ray diffraction for configurational assignments. Bioassays resulted in sclerotiamide J along with five analogs possessing inhibitory effects against LDH and IL-1ß expression in BV-2 cells. Further investigation revealed that sclerotiamide J significantly inhibited NLRP3 inflammasome activation and blocked NLRP3 inflammasome-induced pyroptosis via amelioration of mitochondria damage. In addition, sclerotiamide L exhibited potent inhibition against pathogenic Staphylococcus aureus ATCC 29213 with MIC value of 4.0 µM and the growth of MRSA T144 and Enterococcus faecalis ATCC 29212. This study extends the chemical diversity of notoamide-type alkaloids, and provides potential anti-inflammasome and antibacterial lead compounds for further structure optimization.

Versicotide G suppresses osteoclastogenesis and prevents osteolysis.

Excessive formation and function of osteoclasts cause various osteolytic bone diseases. Natural products are a potential source for the discovery of new therapeutic candidates to treat bone destruction diseases. In this study, chemical informatics and bioassay guided examination of the marine-derived Aspergillus versicolor F77 fungus chemically resulted in the isolation of seven cyclopeptides, of which versicotides G-J (1-4) are new cyclohexapeptides. Their structures were identified by spectroscopic data in association with Marfey method and single crystal X-ray diffraction data for configurational assignments. Bioassay revealed that versicotide G (1, VG) is the most active among the analogs to suppress the receptor activator of nuclear factor-KB ligand (RANKL)-induced osteoclastogenesis in bone marrow derived monocytes (BMMs) without affecting BMMs viability. VG also suppressed RANKL-induced actin-ring formation and resorbing function of osteoclast dose-dependently. Mechanistically, VG attenuated RANKL-induced intracellular calcium elevation by inhibiting PLCγ1 phosphorylation and blocking the activation of downstream phosphatase calcineurin. In addition, VG abrogated the expression and translocation of nuclear factor of activated T cells cytoplasmic-1 (NFATc1), leading to the downregulation of the expression of osteoclast-specific genes and the abolishment of the osteoclast formation. In the in vivo test, VG suppressed osteoclast formation and bone loss in Ti-induced calvarial osteolytic mouse model.These findings imply that VG is a promising candidate for the remedy of bone destruction-related diseases.

Sinuscalide A: An Antiviral Norcembranoid with an 8/8-Fused Carbon Scaffold from the South China Sea Soft Coral Sinularia scabra.

Sinuscalide A (1), featuring an uncommon 8/8-fused carbon scaffold, three new norditerpenes, sinuscalides B-D (2-4), and sinuscatone A (5), with a 5/4/9 tricyclic carbon ring system, along with four known compounds were isolated from the South China Sea soft coral Sinularia scabra. The structures of the new compounds were established by extensive spectroscopic analysis, X-ray diffraction, and electronic circular dichroism (ECD). A plausible biosynthetic pathway for 1 was proposed. In a bioassay, compound 1 showed antiviral activity against human enterovirus EV71 (IC50 = 5.0 µM) and an inhibitory effect against RANKL-induced osteoclastogenesis (92.3% inhibition at 10 µM). Compound 5 exhibited mild inhibition against Streptococcus pneumoniae and Salmonella paratyph (MIC 16 µg/mL).