New Marine Fungal Deoxy-14,15-Dehydroisoaustamide Resensitizes Prostate Cancer Cells to Enzalutamide.

Marine fungi serve as a valuable source for new bioactive molecules bearing various biological activities. In this study, we report on the isolation of a new indole diketopiperazine alkaloid deoxy-14,15-dehydroisoaustamide (1) from the marine-derived fungus Penicillium dimorphosporum KMM 4689 associated with a soft coral. The structure of this metabolite, including its absolute configuration, was determined by HR-MS, 1D and 2D NMR as well as CD data. Compound 1 is a very first deoxyisoaustamide alkaloid possessing two double bonds in the proline ring. The isolated compound was noncytotoxic to a panel of human normal and cancer cell lines up to 100 µM. At the same time, compound 1 resensitized prostate cancer 22Rv1 cells to androgen receptor (AR) blocker enzalutamide. The mechanism of this phenomenon was identified as specific drug-induced degradation of androgen receptor transcription variant V7 (AR-V7), which also resulted in general suppression of AR signaling. Our data suggest that the isolated alkaloid is a promising candidate for combinational therapy of castration resistant prostate cancer, including drug-resistant subtypes.

Anthraquinone Derivatives and Other Aromatic Compounds from Marine Fungus Asteromyces cruciatus KMM 4696 and Their Effects against Staphylococcus aureus.

New anthraquinone derivatives acruciquinones A-C (1-3), together with ten known metabolites, were isolated from the obligate marine fungus Asteromyces cruciatus KMM 4696. Acruciquinone C is the first member of anthraquinone derivatives with a 6/6/5 backbone. The structures of isolated compounds were established based on NMR and MS data. The absolute stereoconfigurations of new acruciquinones A-C were determined using ECD and quantum chemical calculations (TDDFT approach). A plausible biosynthetic pathway of the novel acruciquinone C was proposed. Compounds 1-4 and 6-13 showed a significant antimicrobial effects against Staphylococcus aureus growth, and acruciquinone A (1), dendryol B (4), coniothyrinone B (7), and ω-hydroxypachybasin (9) reduced the activity of a key staphylococcal enzyme, sortase A. Moreover, the compounds, excluding 4, inhibited urease activity. We studied the effects of anthraquinones 1, 4, 7, and 9 and coniothyrinone D (6) in an in vitro model of skin infection when HaCaT keratinocytes were cocultivated with S. aureus. Anthraquinones significantly reduce the negative impact of S. aureus on the viability, migration, and proliferation of infected HaCaT keratinocytes, and acruciquinone A (1) revealed the most pronounced effect.

New Bioactive ß-Resorcylic Acid Derivatives from the Alga-Derived Fungus Penicillium antarcticum KMM 4685.

Five new ß-resorcylic acid derivatives, 14-hydroxyasperentin B (1), ß-resoantarctines A-C (3, 5, 6) and 8-dehydro-ß-resoantarctine A (4), together with known 14-hydroxyasperentin (5'-hydroxyasperentin) (2), were isolated from the ethyl acetate extract of the fungus Penicillium antarcticum KMM 4685 associated with the brown alga Sargassum miyabei. The structures of the compounds were elucidated by spectroscopic analyses and modified Mosher's method, and the biogenetic pathways for compounds 3-6 were proposed. For the very first time, the relative configuration of the C-14 center of a known compound 2 was assigned via analyses of magnitudes of the vicinal coupling constants. The new metabolites 3-6 were biogenically related to resorcylic acid lactones (RALs); however, they did not possess lactonized macrolide elements in their structures. Compounds 3, 4 and 5 exhibited moderate cytotoxic activity in LNCaP, DU145 and 22Rv1 human prostate cancer cells. Moreover, these metabolites could inhibit the activity of p-glycoprotein at their noncytotoxic concentrations and consequently synergize with docetaxel in p-glycoprotein-overexpressing drug-resistant cancer cells.

New Cyclopiane Diterpenes and Polyketide Derivatives from Marine Sediment-Derived Fungus Penicillium antarcticum KMM 4670 and Their Biological Activities.

Two new cyclopiane diterpenes and a new cladosporin precursor, together with four known related compounds, were isolated from the marine sediment-derived fungus Penicillium antarcticum KMM 4670, which was re-identified based on phylogenetic inference from ITS, BenA, CaM, and RPB2 gene regions. The absolute stereostructures of the isolated cyclopianes were determined using modified Mosher's method and quantum chemical calculations of the ECD spectra. The isolation from the natural source of two biosynthetic precursors of cladosporin from a natural source has been reported for the first time. The antimicrobial activities of the isolated compounds against Staphylococcus aureus, Escherichia coli, and Candida albicans as well as the inhibition of staphylococcal sortase A activity were investigated. Moreover, the cytotoxicity of the compounds to mammalian cardiomyocytes H9c2 was studied. As a result, new cyclopiane diterpene 13-epi-conidiogenone F was found to be a sortase A inhibitor and a promising anti-staphylococcal agent.

Absolute Stereochemistry and Cytotoxic Effects of Vismione E from Marine Sponge-Derived Fungus Aspergillus sp. 1901NT-1.2.2.

The metabolic profile of the Aspergillus sp. 1901NT-1.2.2 sponge-associated fungal strain was investigated using the HPLC MS technique, and more than 23 peaks in the HPLC MS chromatogram were detected. Only two minor peaks were identified as endocrocin and terpene derivative MS data from the GNPS database. The main compound was isolated and identified as known anthraquinone derivative vismione E. The absolute stereochemistry of vismione E was established for the first time using ECD and quantum chemical methods. Vismione E showed high cytotoxic activity against human breast cancer MCF-7 cells, with an IC50 of 9.0 µM, in comparison with low toxicity for normal human breast MCF-10A cells, with an IC50 of 65.3 µM. It was found that vismione E inhibits MCF-7 cell proliferation and arrests the cell cycle in the G1 phase. Moreover, the negative influence of vismione E on MCF-7 cell migration was detected. Molecular docking of vismione E suggested the IMPDH2 enzyme as one of the molecular targets for this anthraquinone derivative.

Bioactive Polyketides from the Natural Complex of the Sea Urchin-Associated Fungi Penicillium sajarovii KMM 4718 and Aspergillus protuberus KMM 4747.

The marine-derived fungal strains KMM 4718 and KMM 4747 isolated from sea urchin Scaphechinus mirabilis as a natural fungal complex were identified as Penicillium sajarovii and Aspergillus protuberus based on Internal Transcribed Spacer (ITS), partial ß-tubulin (BenA), and calmodulin (CaM) molecular markers as well as an ribosomal polymerase two, subunit two (RPB2) region for KMM 4747. From the ethyl acetate extract of the co-culture, two new polyketides, sajaroketides A (1) and B (2), together with (2'S)-7-hydroxy-2-(2'-hydroxypropyl)-5-methylchromone (3), altechromone A (4), norlichexanthone (5), griseoxanthone C (6), 1,3,5,6-tetrahydroxy-8-methylxanthone (7), griseofulvin (8), 6-O-desmethylgriseofulvin (9), dechlorogriseofulvin (10), and 5,6-dihydro-4-methyl-2H-pyran-2-one (11) were identified. The structures of the compounds were elucidated using spectroscopic analyses. The absolute configurations of the chiral centers of sajaroketides A and B were determined using time-dependent density functional theory (TDDFT)-based calculations of the Electronic Circular Dichroism (ECD) spectra. The inhibitory effects of these compounds on urease activity and the growth of Staphylococcus aureus, Escherichia coli, and Candida albicans were observed. Sajaroketide A, altechromone A, and griseofulvin showed significant cardioprotective effects in an in vitro model of S. aureus-induced infectious myocarditis.

Meroantarctines A-C, Meroterpenoids with Rearranged Skeletons from the Alga-Derived Fungus Penicillium antarcticum KMM 4685 with Potent p-Glycoprotein Inhibitory Activity.

New meroterpenoids, meroantarctines A-C (1-3), with unique 6/5/6/6, 6/5/6/5/6, and 6/5/6/5 polycyclic systems were isolated from the alga-derived fungus Penicillium antarcticum KMM 4685. Their structures were elucidated by spectroscopic methods, X-ray diffraction, and quantum chemical calculations. A biogenetic pathway for 1-3 was proposed. Meroantarctines A-C (1-3) inhibited p-glycoprotein activity and could resensitize drug-resistant cancer cells to docetaxel.

New Tripeptide Derivatives Asperripeptides A-C from Vietnamese Mangrove-Derived Fungus Aspergillus terreus LM.5.2.

Three new tripeptide derivatives asterripeptides A-C (1-3) were isolated from Vietnamese mangrove-derived fungus Aspergillus terreus LM.5.2. Structures of isolated compounds were determined by a combination of NMR and ESIMS techniques. The absolute configurations of all stereocenters were determined using the Murfey's method. The isolated compounds 1-3 contain a rare fungi cinnamic acid residue. The cytotoxicity of isolated compounds against several cancer cell lines and inhibition ability of sortase A from Staphylococcus aureus of asterripeptides A-C were investigated.

Cytotoxic N-Methylpretrichodermamide B Reveals Anticancer Activity and Inhibits P-Glycoprotein in Drug-Resistant Prostate Cancer Cells.

N-methylpretrichodermamide B (NB) is a biologically active epidithiodiketopiperazine isolated from several strains of the algae-derived fungus Penicillium sp. Recently, we reported the first data on its activity in human cancer cells lines in vitro. Here, we investigated the activity, selectivity, and mechanism of action of NB in human prostate cancer cell lines, including drug-resistant subtypes. NB did not reveal cross-resistance to docetaxel in the PC3-DR cell line model and was highly active in hormone-independent 22Rv1 cells. NB-induced cell death was stipulated by externalization of phosphatidylserine and activation of caspase-3. Moreover, inhibition of caspase activity by z-VAD(OMe)-fmk did not affect NB cytotoxicity, suggesting a caspase-independent cell death induced by NB. The compound has a moderate p-glycoprotein (p-gp) substrate-like affinity and can simultaneously inhibit p-gp at nanomolar concentrations. Therefore, NB resensitized p-gp-overexpressing PC3-DR cells to docetaxel. A kinome profiling of the NB-treated cells revealed, among other things, an induction of mitogen-activated protein kinases JNK1/2 and p38. Further functional analysis confirmed an activation of both kinases and indicated a prosurvival role of this biological event in the cellular response to the treatment. Overall, NB holds promising anticancer potential and further structure-activity relationship studies and structural optimization are needed in order to improve its biological properties.

Cytotoxic Drimane-Type Sesquiterpenes from Co-Culture of the Marine-Derived Fungi Aspergillus carneus KMM 4638 and Beauveria felina (=Isaria felina) KMM 4639.

Chemical investigation of a coculture of the marine-derived fungi Beauveria felina KMM 4639 and Aspergillus carneus KMM 4638 led to the identification of three new drimane-type sesquiterpenes, asperflavinoids B, D and E (2, 4, 5), and nine previously reported related compounds. The structures of these compounds were established using spectroscopic methods and by comparison with known analogues. We also investigated the cytotoxic activity of the isolated compounds against several cancer and normal cell lines. Asperflavinoid C (3) and ustusolate E (9) exerted a significant effect on human breast cancer MCF-7 cell viability, with IC50 values of 10 µM, and induced in caspase-dependent apoptosis and arrest of the MCF-7 cell cycle in the G2/M phase in these cells.

Cytoprotective Polyketides from Sponge-Derived Fungus Lopadostoma pouzarii.

The new polyketides lopouzanones A and B, as well as the new 1-O-acetyl and 2-O-acetyl derivatives of dendrodochol B, were isolated from the sponge-derived marine fungus Lopadostoma pouzarii strain 168CLC-57.3. Moreover, six known polyketides, gliorosein, balticolid, dendrodolide G, dihydroisocoumarine, (-)-5-methylmellein, and dendrodochol B, were identified. The structures of the isolated compounds were determined by a combination of NMR and ESIMS techniques. The absolute configurations of the lopouzanones A and B were determined using the Mosher's method. The cytotoxicity of the isolated compounds against human prostate cancer cells PC-3 and normal rat cardiomyocytes H9c2 was investigated. Gliorosein showed weak DPPH radical-scavenging activity and in vitro cardioprotective effects toward rotenone toxicity and CoCl2-mimic hypoxia.

Metabolites of Marine Sediment-Derived Fungi: Actual Trends of Biological Activity Studies.

Marine sediments are characterized by intense degradation of sedimenting organic matter in the water column and near surface sediments, combined with characteristically low temperatures and elevated pressures. Fungi are less represented in the microbial communities of sediments than bacteria and archaea and their relationships are competitive. This results in wide variety of secondary metabolites produced by marine sediment-derived fungi both for environmental adaptation and for interspecies interactions. Earlier marine fungal metabolites were investigated mainly for their antibacterial and antifungal activities, but now also as anticancer and cytoprotective drug candidates. This review aims to describe low-molecular-weight secondary metabolites of marine sediment-derived fungi in the context of their biological activity and covers research articles published between January 2016 and November 2020.

Marine Fungal Cerebroside Flavuside B Protects HaCaT Keratinocytes against Staphylococcus aureus Induced Damage.

Cerebrosides are glycosylated sphingolipids, and in mammals they contribute to the pro-/anti-inflammatory properties and innate antimicrobial activity of the skin and mucosal surfaces. Staphylococcus aureus infection can develop, not only from minor scratches of the skin, but this pathogen can also actively promote epithelial breach. The effect of cerebroside flavuside B from marine sediment-derived fungus Penicillium islandicum (Aniva Bay, the Sea of Okhotsk) on viability, apoptosis, total caspase activity, and cell cycle in human epidermal keratinocytes HaCaT line co-cultivated with S. aureus, as well as influence of flavuside B on LPS-treated HaCaT cells were studied. Influence of flavuside B on bacterial growth and biofilm formation of S. aureus and its effect on the enzymatic activity of sortase A was also investigated. It was found S. aureus co-cultivated with keratinocytes induces caspase-depended apoptosis and cell death, arrest cell cycle in the G0/G1 phase, and increases in cellular immune inflammation. Cerebroside flavuside B has demonstrated its antimicrobial and anti-inflammatory properties, substantially eliminating all the negative consequences caused by co-cultivation of keratinocytes with S. aureus or bacterial LPS. The dual action of flavuside B may be highly effective in the treatment of bacterial skin lesions and will be studied in the future in in vivo experiments.

Cytoprotective Activity of p-Terphenyl Polyketides and Flavuside B from Marine-Derived Fungi against Oxidative Stress in Neuro-2a Cells.

The influence of p-terphenyl polyketides 1-3 from Aspergillus candidus KMM 4676 and cerebroside flavuside B (4) from Penicillium islandicum (=Talaromyces islandicus) against the effect of neurotoxins, rotenone and paraquat, on Neuro-2a cell viability by MTT and LDH release assays and intracellular ROS level, as well as DPPH radical scavenging activity, was investigated. Pre-incubation with compounds significantly diminished the ROS level in rotenone- and paraquat-treated cells. It was shown that the investigated polyketides 1-3 significantly increased the viability of rotenone- and paraquat-treated cells in two of the used assays but they affected only the viability of paraquat-treated cells in the LDH release assay. Flavuside B statistically increased the viability of paraquat-treated cells in both MTT and LDH release assays, however, it increased the viability of rotenone-treated cells in the LDH release assay. Structure-activity relationships for p-terphenyl derivatives, as well as possible mechanisms of cytoprotective action of all studied compounds, were discussed.

Neuroprotective Metabolites from Vietnamese Marine Derived Fungi of Aspergillus and Penicillium Genera.

Low molecular weight secondary metabolites of marine fungi Aspergillus flocculosus, Aspergillus terreus and Penicillium sp. from Van Phong and Nha Trang Bays (Vietnam) were studied and a number of polyketides, bis-indole quinones and terpenoids were isolated. The structures of the isolated compounds were determined by 1D and 2D NMR and HR-ESI-MS techniques. Stereochemistry of some compounds was established based on ECD data. A chemical structure of asterriquinone F (6) was thoroughly described for the first time. Anthraquinone (13) was firstly obtained from a natural source. Neuroprotective influences of the isolated compounds against 6-OHDA, paraquat and rotenone toxicity were investigated. 4-Hydroxyscytalone (1), 4-hydroxy-6-dehydroxyscytalone (2) and demethylcitreoviranol (3) have shown significant increasing of paraquat- and rotenone-treated Neuro-2a cell viability and anti-ROS activity.

Biologically Active Metabolites from the Marine Sediment-Derived Fungus Aspergillus flocculosus.

Four new compounds were isolated from the Vietnamese marine sediment-derived fungus Aspergillus flocculosus, one aspyrone-related polyketide aspilactonol G (2), one meroterpenoid 12-epi-aspertetranone D (4), two drimane derivatives (7,9), together with five known metabolites (1,3,5,6,8,10). The structures of compounds 1-10 were established by NMR and MS techniques. The absolute stereoconfigurations of compounds 1 and 2 were determined by a modified Mosher's method. The absolute configurations of compounds 4 and 7 were established by a combination of analysis of ROESY data and coupling constants as well as biogenetic considerations. Compounds 7 and 8 exhibited cytotoxic activity toward human prostate cancer 22Rv1, human breast cancer MCF-7, and murine neuroblastoma Neuro-2a cells.

Achievements in the Study of Marine Low-Molecular Weight Biologically Active Metabolites from the Vietnamese Territorial Waters as a Result of Expeditions aboard the Research Vessel 'Akademik Oparin' (2004-2017).

Until 2004, the secondary metabolites of marine organisms of the Vietnamese territorial waters had been studied very poorly. Only four new compounds were isolated from 1977 to 2003. Joint Russian-Vietnamese expeditions aboard the research vessel 'Akademik Oparin' made it possible to study in detail the chemical diversity of marine micro- and macroorganisms. As a result of five expeditions, more than 250 low-molecular weight natural compounds, including 117 new metabolites, were isolated from marine invertebrates and microfilamentous fungi. Their biological activities, such as cytotoxic, cytoprotective, and antioxidant activities, were investigated. Information about the structure and biological activity of the compounds, the source for their isolation and the geographical location of the objects is summarized in this review.

Biologically Active Echinulin-Related Indolediketopiperazines from the Marine Sediment-Derived Fungus Aspergillus niveoglaucus.

Seven known echinulin-related indolediketopiperazine alkaloids (1-7) were isolated from the Vietnamese sediment-derived fungus Aspergillus niveoglaucus. Using chiral HPLC, the enantiomers of cryptoechinuline B (1) were isolated as individual compounds for the first time. (+)-Cryptoechinuline B (1a) exhibited neuroprotective activity in 6-OHDA-, paraquat-, and rotenone-induced in vitro models of Parkinson's disease. (-)-Cryptoechinuline B (1b) and neoechinulin C (5) protected the neuronal cells against paraquat-induced damage in a Parkinson's disease model. Neoechinulin B (4) exhibited cytoprotective activity in a rotenone-induced model, and neoechinulin (7) showed activity in the 6-OHDA-induced model.

Neuroprotective Activity of Some Marine Fungal Metabolites in the 6-Hydroxydopamin- and Paraquat-Induced Parkinson's Disease Models.

A new melatonin analogue 6-hydroxy-N-acetyl-ß-oxotryptamine (1) was isolated from the marine-derived fungus Penicillium sp. KMM 4672. It is the second case of melatonin-related compounds isolation from microfilamentous fungi. The neuroprotective activities of this metabolite, as well as 3-methylorsellinic acid (2) and 8-methoxy-3,5-dimethylisochroman-6-ol (3) from Penicillium sp. KMM 4672, candidusin A (4) and 4″-dehydroxycandidusin A (5) from Aspergillus sp. KMM 4676, and diketopiperazine mactanamide (6) from Aspergillus flocculosus, were investigated in the 6-hydroxydopamine (6-OHDA)- and paraquat (PQ)-induced Parkinson's disease (PD) cell models. All of them protected Neuro2a cells against the damaging influence of 6-OHDA to varying degrees. This effect may be realized via a reactive oxygen species (ROS) scavenging pathway. The new melatonin analogue more effectively protected Neuro2A cells against the 6-OHDA-induced neuronal death, in comparison with melatonin, as well as against the PQ-induced neurotoxicity. Dehydroxylation at C-3″ and C-4″ significantly increased free radical scavenging and neuroprotective activity of candidusin-related p-terphenyl polyketides in both the 6-OHDA- and PQ-induced PD models.

Asperindoles A⁻D and a p-Terphenyl Derivative from the Ascidian-Derived Fungus Aspergillus sp. KMM 4676.

Four new indole-diterpene alkaloids asperindoles A⁻D (1⁻4) and the known p-terphenyl derivative 3″-hydroxyterphenyllin (5) were isolated from the marine-derived strain of the fungus Aspergillus sp., associated with an unidentified colonial ascidian. The structures of 1⁻5 were established by 2D NMR and HRESIMS data. The absolute configurations of all stereocenters of 1⁻4 were determined by the combination of ROESY data, coupling constants analysis, and biogenetic considerations. Asperindoles C and D contain a 2-hydroxyisobutyric acid (2-HIBA) residue, rarely found in natural compounds. Asperindole A exhibits cytotoxic activity against hormone therapy-resistant PC-3 and 22Rv1, as well as hormone therapy-sensitive human prostate cancer cells, and induces apoptosis in these cells at low-micromolar concentrations.