A New Meroditerpene and a New Tryptoquivaline Analog from the Algicolous Fungus Neosartorya takakii KUFC 7898

New prenylated indole-benzodiazepine-2,5-diones with α-glucosidase inhibitory activities from the mangrove-derived Aspergillus spinosus

Mangrove-derived fungi have been demonstrated to be promising source of structurally diverse and widely active secondary metabolites. During our search for new bioactive compounds, eight new indole-benzodiazepine-2,5-dione derivatives asperdinones A-H (1-8) and two known congeners (9 and 10) were isolated from the culture extracts of the mangrove-derived fungus Aspergillus spinosus WHUF0344 guided by one strain many compounds (OSMAC) and the heteronuclear 1H, 13C single-quantum coherence (HSQC) based small molecule accurate recognition technology (SMART) strategies. The structures and absolute configurations of the new compounds were elucidated by detailed spectroscopic analyze and electronic circular dichroism (ECD) calculations. The putative biosynthetic pathway of these compounds was proposed. Compounds 1-10 were evaluated for their antibacterial and α-glucosidase inhibitory activities. None of compounds showed antibacterial activity. Compounds 2-6 and 8 exhibited moderate inhibitory effects against α-glucosidase with IC50 values in the range of 24.65-312.25 μM. Besides, both 3 and 4 inhibited α-glucosidase variedly. Furthermore, the molecular docking study showed that compounds 2-4 were perfectly docking into the active sites of α-glucosidase. This study not only enriched the chemical diversity of secondary metabolites from the mangrove-derived fungi, but also provided potential hit compounds for further development of α-glucosidase inhibitors.

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.

Unravelling the Secrets of α-Pyrones from Aspergillus Fungi: A Comprehensive Review of Their Natural Sources, Biosynthesis, and Biological Activities

Aspergillus, one of the most product-rich and genetically robust genera, contains a diverse range of species with potential economic and ecological implications. Chemically, Aspergillus is one of the essential sources of polyketides, alkaloids, diphenyl ethers, diketopiperazines, and other miscellaneous compounds, displaying a variety of pharmacological activities. The α-pyrones are unsaturated six-membered lactones. Although α-pyrone has a small structure, it is responsible for the structural diversity of several natural and synthetic compounds and multiple biological activities. In this review, we have summarized approximately 178 α-pyrone containing metabolites derivatives identified/reported from terrestrial, marine, endophytic, and filamentous Aspergillus species, including their sources, biological properties, and biosynthetic pathways until mid-2023, for the first time. This review is the first to compile and analyze the available data on α-pyrone metabolites from Aspergillus, which could facilitate further research and innovation in this field. Additionally, it offers a valuable source of scaffolds for future bioactive drug development, as some of these metabolites have shown potent antimicrobial, anti-inflammatory, and anticancer effects. Therefore, this review has significant implications for the advancement of natural product chemistry, pharmacology, biotechnology, and medicine.

Peptides from Marine-Derived Fungi: Chemistry and Biological Activities

Marine natural products are well-recognized as potential resources to fill the pipeline of drug leads to enter the pharmaceutical industry. In this circumstance, marine-derived fungi are one of the unique sources of bioactive secondary metabolites due to their capacity to produce diverse polyketides and peptides with unique structures and diverse biological activities. The present review covers the peptides from marine-derived fungi reported from the literature published from January 1991 to June 2023, and various scientific databases, including Elsevier, ACS publications, Taylor and Francis, Wiley Online Library, MDPI, Springer, Thieme, Bentham, ProQuest, and the Marine Pharmacology website, are used for a literature search. This review focuses on chemical characteristics, sources, and biological and pharmacological activities of 366 marine fungal peptides belonging to various classes, such as linear, cyclic, and depsipeptides. Among 30 marine-derived fungal genera, isolated from marine macro-organisms such as marine algae, sponges, coral, and mangrove plants, as well as deep sea sediments, species of Aspergillus were found to produce the highest number of peptides (174 peptides), followed by Penicillium (23 peptides), Acremonium (22 peptides), Eurotium (18 peptides), Trichoderma (18 peptides), Simplicillium (17 peptides), and Beauveria (12 peptides). The cytotoxic activity against a broad spectrum of human cancer cell lines was the predominant biological activity of the reported marine peptides (32%), whereas antibacterial, antifungal, antiviral, anti-inflammatory, and various enzyme inhibition activities ranged from 7% to 20%. In the first part of this review, the chemistry of marine peptides is discussed and followed by their biological activity.

Thermal shift assays of marine-derived fungal metabolites from Aspergillus fischeri MMERU 23 against Leishmania major pteridine reductase 1 and molecular dynamics studies

Marine-derived fungi are a promising source of bioactive molecules, especially species from extreme habitats. Although several secondary metabolites such as meroterpenoids and alkaloids have been isolated from cultures of Aspergillus fischeri, obtained from terrestrial habitats, there is no report on compounds isolated from marine-derived strains. Many metabolites isolated from marine-derived fungi exhibited a myriad of biological activities. Marine natural products have shown to be an important source of bioactive compounds and can assist in the discovery of molecules with affinity against validated targets from exclusive strains of parasites of medical importance such as pteridine reductase 1 (PTR1), from Leishmania major, which is essential for cell growth. Leishmaniasis is responsible for approximately 65,000 annual deaths. Despite the mortality data, drugs available for the treatment of patients are insufficient and have moderate therapeutic efficacy in addition to serious adverse effects, which make the development of new drugs urgent. The previously described aszonalenin (ASL), aszonapyrone A (ASP), acetylaszonalenin (ACZ), and helvolic acid (HAC) were isolated from the ethyl acetate extract of the culture of a marine sponge-associated A. fischeri MMERU 23 and their affinities against PTR1 were determined by ThermoFluor®. Among the tested compounds, only ACZ showed dose-dependent affinity against PTR1. Moreover, complementary molecular dynamics studies (t = 100 000 ps) have showed that this molecule performs hydrogen bonds with key residues at the active site for more than 60% of the productive trajectory time. The results indicate that ACZ could be a promising PTR1 inhibitor and a potential candidate for development of antileishmanial drug.Communicated by Ramaswamy H. Sarma.

Bioactive Compounds from Terrestrial and Marine-Derived Fungi of the Genus Neosartorya †

Fungi comprise the second most species-rich organism group after that of insects. Recent estimates hypothesized that the currently reported fungal species range from 3.5 to 5.1 million types worldwide. Fungi can grow in a wide range of habitats, from the desert to the depths of the sea. Most develop in terrestrial environments, but several species live only in aquatic habitats, and some live in symbiotic relationships with plants, animals, or other fungi. Fungi have been proved to be a rich source of biologically active natural products, some of which are clinically important drugs such as the β-lactam antibiotics, penicillin and cephalosporin, the immunosuppressant, cyclosporine, and the cholesterol-lowering drugs, compactin and lovastatin. Given the estimates of fungal biodiversity, it is easy to perceive that only a small fraction of fungi worldwide have ever been investigated regarding the production of biologically valuable compounds. Traditionally, fungi are classified primarily based on the structures associated with sexual reproduction. Thus, the genus Neosartorya (Family Trichocomaceae) is the telemorphic (sexual state) of the Aspergillus section known as Fumigati, which produces both a sexual state with ascospores and an asexual state with conidiospores, while the Aspergillus species produces only conidiospores. However, according to the Melbourne Code of nomenclature, only the genus name Aspergillus is to be used for both sexual and asexual states. Consequently, the genus name Neosartorya was no longer to be used after 1 January 2013. Nevertheless, the genus name Neosartorya is still used for the fungi that had already been taxonomically classified before the new rule was in force. Another aspect is that despite the small number of species (23 species) in the genus Neosartorya, and although less than half of them have been investigated chemically, the chemical diversity of this genus is impressive. Many chemical classes of compounds, some of which have unique scaffolds, such as indole alkaloids, peptides, meroterpenes, and polyketides, have been reported from its terrestrial, marine-derived, and endophytic species. Though the biological and pharmacological activities of a small fraction of the isolated metabolites have been investigated due to the available assay systems, they exhibited relevant biological and pharmacological activities, such as anticancer, antibacterial, antiplasmodial, lipid-lowering, and enzyme-inhibitory activities.

Natural Indole Alkaloids from Marine Fungi: Chemical Diversity and Biological Activities

The indole scaffold is one of the most important heterocyclic ring systems for pharmaceutical development, and serves as an active moiety in several clinical drugs. Fungi derived from marine origin are more liable to produce novel indole-containing natural products due to their extreme living environments. The indole alkaloids from marine fungi have drawn considerable attention for their unique chemical structures and significant biological activities. This review attempts to provide a summary of the structural diversity of marine fungal indole alkaloids including prenylated indoles, diketopiperazine indoles, bisindoles or trisindoles, quinazoline-containing indoles, indole-diterpenoids, and other indoles, as well as their known biological activities, mainly focusing on cytotoxic, kinase inhibitory, antiinflammatory, antimicrobial, anti-insecticidal, and brine shrimp lethal effects. A total of 306 indole alkaloids from marine fungi have been summarized, covering the references published from 1995 to early 2021, expecting to be beneficial for drug discovery in the future.

Three New Metabolites From the Marine-Derived Fungus Aspergillus sp. WHUF03110

Two new xanthone derivatives, spinosusones A (1) and B (2), and a new tryptoquivaline analogue, asperdiazapinone G (3), together with nine known compounds (4-12) were isolated from the EtOAc extract of the marine-derived fungus Aspergillus sp . WHUF03110. The structures of 1-3 were determined by spectroscopic analysis, and comparison with literature data. Most of these isolated compounds were evaluated for their antimicrobial activities against ten Gram-negative and seven Gram-positive bacteria, Mycobacterium smegmatis ATCC 607, Candida albicans ATCC SC5314, and C. albicans YY-1-4. Compound 10 displayed strong antibacterial activity against five Gram-positive bacteria ( Bacillus subtilis 168, Staphylococcus aureus ATCC25923, S. aureus NEWMAN, S. aureus USA300, S. aureus NRS 271) with MIC values ranging from 1.0 to 2.0 μg/mL, and displayed moderate antibacterial activity against four Gram-negative bacteria ( Helicobacter pylori 26695, H. pylori G27, H. pylori 159, H. pylori 129) and M. smegmatis ATCC 607 with a MIC value of 8.0 μg/mL.

Metabolites from Marine-Derived Fungi as Potential Antimicrobial Adjuvants

Marine-derived fungi constitute an interesting source of bioactive compounds, several of which exhibit antibacterial activity. These acquire special importance, considering that antimicrobial resistance is becoming more widespread. The overexpression of efflux pumps, capable of expelling antimicrobials out of bacterial cells, is one of the most worrisome mechanisms. There has been an ongoing effort to find not only new antimicrobials, but also compounds that can block resistance mechanisms which can be used in combination with approved antimicrobial drugs. In this work, a library of nineteen marine natural products, isolated from marine-derived fungi of the genera Neosartorya and Aspergillus, was evaluated for their potential as bacterial efflux pump inhibitors as well as the antimicrobial-related mechanisms, such as inhibition of biofilm formation and quorum-sensing. Docking studies were performed to predict their efflux pump action. These compounds were also tested for their cytotoxicity in mouse fibroblast cell line NIH/3T3. The results obtained suggest that the marine-derived fungal metabolites are a promising source of compounds with potential to revert antimicrobial resistance and serve as an inspiration for the synthesis of new antimicrobial drugs.

Anthraquinones, Diphenyl Ethers, and Their Derivatives from the Culture of the Marine Sponge-Associated Fungus Neosartorya spinosa KUFA 1047

Previously unreported anthraquinone, acetylpenipurdin A (4), biphenyl ether, neospinosic acid (6), dibenzodioxepinone, and spinolactone (7) were isolated, together with (R)-6-hydroxymellein (1), penipurdin A (2), acetylquestinol (3), tenellic acid C (5), and vermixocin A (8) from the culture of a marine sponge-associated fungus Neosartorya spinosa KUFA1047. The structures of the previously unreported compounds were established based on an extensive analysis of 1D and 2D NMR spectra as well as HRMS data. The absolute configurations of the stereogenic centers of 5 and 7 were established unambiguously by comparing their calculated and experimental electronic circular dichroism (ECD) spectra. Compounds 2 and 5–8 were tested for their in vitro acetylcholinesterase and tyrosinase inhibitory activities as well as their antibacterial activity against Gram-positive and Gram-negative reference, and multidrug-resistant strains isolated from the environment. The tested compounds were also evaluated for their capacity to inhibit biofilm formation in the reference strains.

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

Isolation, chemistry, and biology of pyrrolo[1,4]benzodiazepine natural products

The isolation of the antitumor antibiotic anthramycin in the 1960s prompted extensive research into pyrrolo[1,4]benzodiazepines (PBD) as potential therapeutics for the treatment of cancers. Since then, nearly 60 PBD natural products have been isolated and evaluated with regard to their biological activity. Synthetic studies and total syntheses have enabled access to PBD analogues, culminating in the development of highly potent anticancer agents. This review provides a summary of the occurrence and biological activity of PBD natural products and covers the strategies employed for their total syntheses.

Marine-derived fungi as a source of bioactive indole alkaloids with diversified structures

Marine-derived fungi are well known as rich sources of bioactive natural products. Growing evidences indicated that indole alkaloids, isolated from a variety of marine-derived fungi, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities, and therefore, indole alkaloids have potential to be pharmaceutical lead compounds. Systemic compilation of the relevant literature. In this review, we demonstrated a comprehensive overview of 431 new indole alkaloids from 21 genera of marine-derived fungi with an emphasis on their structures and bioactivities, covering literatures published during 1982-2019.

4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle: A promising scaffold towards bioactive molecules

The quinazolinone nucleus represents, among the class of fused heterocycles, a very important scaffold to obtain molecules with biological activities. A review of literature revealed how such kind of fused heterocycles, coming from natural or synthetic source, are associated with a wide range of biological activities. This review is mainly directed towards the 4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle in which all the possible combinations of nitrogen, sulfur and oxygen atoms are present.

Recent advances in indole dimers and hybrids with antibacterial activity against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), one of the major and most dangerous pathogens in humans, is a causative agent of severe pandemic of mainly skin and soft tissue and occasionally fatal infections. Therefore, it is imperative to develop potent and novel anti-MRSA agents. Indole derivatives could act against diverse enzymes and receptors in bacteria, occupying a salient place in the development of novel antibacterial agents. Dimerization and hybridization are common strategies to discover new drugs, and a number of indole dimers and hybrids possess potential antibacterial activity against a panel of clinically important pathogens including MRSA. Accordingly, indole dimers and hybrids are privileged scaffolds for the discovery of novel anti-MRSA agents. This review outlines the recent development of indole dimers and hybrids with a potential activity against MRSA, covering articles published between 2010 and 2020. The structure-activity relationship and the mechanism of action are also discussed to facilitate further rational design of more effective candidates.

A Review of Terpenes from Marine-Derived Fungi: 2015-2019

Marine-derived fungi are a significant source of pharmacologically active metabolites with interesting structural properties, especially terpenoids with biological and chemical diversity. In the past five years, there has been a tremendous increase in the rate of new terpenoids from marine-derived fungi being discovered. In this updated review, we examine the chemical structures and bioactive properties of new terpenes from marine-derived fungi, and the biodiversity of these fungi from 2015 to 2019. A total of 140 research papers describing 471 new terpenoids of six groups (monoterpenes, sesquiterpenes, diterpenes, sesterterpenes, triterpenes, and meroterpenes) from 133 marine fungal strains belonging to 34 genera were included. Among them, sesquiterpenes, meroterpenes, and diterpenes comprise the largest proportions of terpenes, and the fungi genera of Penicillium, Aspergillus, and Trichoderma are the dominant producers of terpenoids. The majority of the marine-derived fungi are isolated from live marine matter: marine animals and aquatic plants (including mangrove plants and algae). Moreover, many terpenoids display various bioactivities, including cytotoxicity, antibacterial activity, lethal toxicity, anti-inflammatory activity, enzyme inhibitor activity, etc. In our opinion, the chemical diversity and biological activities of these novel terpenoids will provide medical and chemical researchers with a plenty variety of promising lead compounds for the development of marine drugs.

Natural indole-containing alkaloids and their antibacterial activities

As the growth in resistance to bacterial infection treatments poses a grave threat to global health in the 21st century, there is a constant need to explore novel antibacterial agents that have the ability to overcome drug resistance. Indole-containing alkaloids are widely distributed in nature, and a variety of indole-containing alkaloids have already been applied in clinical practice, proving that indole-containing alkaloids are fascinating and privileged scaffolds for the development of novel drugs. Moreover, indole-containing alkaloids could exert their antibacterial activity through the inhibition of efflux pumps, the biofilm, filamentous temperature-sensitive protein Z, and methicillin-resistant Staphylococcus aureus pyruvate kinase; so, indole-containing alkaloids constitute an important source of novel antibacterial agents. This review is an endeavor to highlight the advances in the development of indole-containing alkaloids with antibacterial potential, covering articles published in the recent 10 years.

Chemical Diversity and Biological Activities of Meroterpenoids from Marine Derived-Fungi: A Comprehensive Update

Meroterpenoids are a class of hybrid natural products, partially derived from a mixed terpenoid pathway. They possess remarkable structural features and relevant biological and pharmacological activities. Marine-derived fungi are a rich source of meroterpenoids featuring structural diversity varying from simple to complex molecular architectures. A combination of a structural variability and their myriad of bioactivities makes meroterpenoids an interesting class of naturally occurring compounds for chemical and pharmacological investigation. In this review, a comprehensive literature survey covering the period of 2009–2019, with 86 references, is presented focusing on chemistry and biological activities of various classes of meroterpenoids isolated from fungi obtained from different marine hosts and environments.

Potential Antidiabetic Fumiquinazoline Alkaloids from the Marine-Derived Fungus Scedosporium apiospermum F41-1

Fumiquinazoline alkaloids have attracted much attention from medicinal and natural product chemists due to their interesting structures and biological potential. In this study, three new and 12 known fumiquinazoline alkaloids were isolated and characterized from the marine fungus Scedosporium apiospermum F41-1. The structures of the new compounds and their absolute configurations were determined using NMR spectroscopy, ECD, and OR calculations. The compounds were evaluated for their antidiabetic potential by determining their triglyceride-promoting activity using 3T3-L1 adipocytes. One of the new compounds, scequinadoline J (14), as well as scequinadolines D (9) and E (10), was found to promote triglyceride accumulation in 3T3-L1 cells. Scequinadoline D (9) demonstrated the most potent activity, with an EC₅₀ value of 0.27 ± 0.03 μM. Quantitative polymerase chain reaction experiments suggested that scequinadoline D (9) acts through activation of the PPARγ pathway. It stimulated the mRNA expression of PPARγ, AMPKα, C/EBPα, LXRα, SCD-1, and FABP4. In addition, its triglyceride-promoting efficacy could be blocked by a double dose of the PPARγ antagonist GW9662. These results indicated that scequinadoline D (9) is a potent insulin sensitizer that targets adipocytes and may be useful for the treatment of type 2 diabetes mellitus after further investigation.

Tryptoquivalines W and X, two new compounds from a Hawaiian fungal strain and their biological activities

Two new compounds tryptoquivalines W (1) and X (2) were isolated from a Hawaiian soil fungal strain Aspergillus terreus FS107. The soil sample was collected on the top of Mauna Kea, the tallest mountain in Hawaii. The structures of compounds 1 and 2 were determined on the basis of MS spectroscopic and NMR analysis, and NMR calculation. The absolute configuration (AC) was determined by ECD calculations. Compounds 4 and 5 showed inhibition against NF-κB with IC50 values of 3.45 and 6.76 μM, respectively.

A New Dihydrochromone Dimer and Other Secondary Metabolites from Cultures of the Marine Sponge-Associated Fungi Neosartorya fennelliae KUFA 0811 and Neosartorya tsunodae KUFC 9213

A previously unreported dihydrochromone dimer, paecilin E (1), was isolated, together with eleven known compounds: β-sitostenone, ergosta-4,6,8 (14), 22-tetraen-3-one, cyathisterone, byssochlamic acid, dehydromevalonic acid lactone, chevalone B, aszonalenin, dankasterone A (2), helvolic acid, secalonic acid A and fellutanine A, from the culture filtrate extract of the marine sponge-associated fungus Neosartorya fennelliae KUFA 0811. Nine previously reported metabolites, including a chromanol derivative (3), (3β, 5α, 22E), 3,5-dihydroxyergosta-7,22-dien-6-one (4), byssochlamic acid, hopan-3β,22-diol, chevalone C, sartorypyrone B, helvolic acid, lumichrome and the alkaloid harmane were isolated from the culture of the marine-sponge associated fungus Neosartorya tsunodae KUFC 9213. Paecilin E (1), dankasterone A (2), a chromanol derivative (3), (3β, 5α, 22E)-3,5-dihydroxyergosta-7,22-dien-6-one (4), hopan-3β,22-diol (5), lumichrome (6), and harmane (7) were tested for their antibacterial activity against Gram-positive and Gram-negative reference and multidrug-resistant strains isolated from the environment. While paecilin E (1) was active against S. aureus ATCC 29213 and E. faecalis ATCC 29212, dankastetrone A (2) was only effective against E. faecalis ATCC 29212 and the multidrug-resistant VRE E. faecalis A5/102. Both compounds neither inhibit biofilm mass production in any of the strains at the concentrations tested nor exhibit synergistic association with antibiotics.

Antibacterial and antibiofilm activities of the metabolites isolated from the culture of the mangrove-derived endophytic fungus Eurotium chevalieri KUFA 0006

Five previously undescribed metabolites, including acetylquestinol, two prenylated indole 3-carbaldehyde derivatives, an anthranilic acid derivative and an isochromone derivative, were isolated, in addition to eleven known compounds: palmitic acid, ergosterol 5,8-endoperoxide, emodin, physcion, questin, questinol, (11S, 14R)-cyclo(tryptophylvalyl), preechinulin, neoechinulin E, echinulin and eurocristatine, from the culture of the endophytic fungus Eurotium chevalieri KUFA 0006. The structures of the previously undescribed compounds were established based on an extensive 1D and 2D NMR spectral analysis as well as HRMS and IR data. In case of 2-(2, 2-dimethylcyclopropyl)-1H-indole-3-carbaldehyde and 6, 8-dihydroxy-3-(2S-hydroxypropyl)-7-methylisochromone, the absolute configurations of their stereogenic carbons were established based on comparison of their experimental and calculated ECD spectra. All the compounds, except for palmitic acid and ergosterol 5, 8-endoperoxide, were evaluated for their antibacterial and antibiofilm activities against two Gram-positive and two Gram-negative bacteria, as well as multidrug-resistant isolates from the environment. Emodin not only exhibited moderate antibacterial activity against the Gram-positive bacteria but also showed strong synergistic association with oxacillin against MRSA Staphylococcus aureus.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) 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 (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

A New Ergosterol Analog, a New Bis-Anthraquinone and Anti-Obesity Activity of Anthraquinones from the Marine Sponge-Associated Fungus Talaromyces stipitatus KUFA 0207

A new ergosterol analog, talarosterone (1) and a new bis-anthraquinone derivative (3) were isolated, together with ten known compounds including palmitic acid, ergosta-4,6,8(14),22-tetraen-3-one, ergosterol-5,8-endoperoxide, cyathisterone (2), emodin (4a), questinol (4b), citreorosein (4c), fallacinol (4d), rheoemodin (4e) and secalonic acid A (5), from the ethyl acetate extract of the culture of the marine sponge-associated fungus Talaromyces stipitatus KUFA 0207. The structures of the new compounds were established based on extensive 1D and 2D spectral analysis, and in the case of talarosterone (1), the absolute configurations of its stereogenic carbons were determined by X-ray crystallographic analysis. The structure and stereochemistry of cyathisterone (2) was also confirmed by X-ray analysis. The anthraquinones 4a-e and secalonic acid A (5) were tested for their anti-obesity activity using the zebrafish Nile red assay. Only citreorosein (4c) and questinol (4b) exhibited significant anti-obesity activity, while emodin (4a) and secalonic acid A (5) caused toxicity (death) for all exposed zebrafish larvae after 24 h.

Structural Analysis of Natural Products

Current mass spectrometry, nuclear magnetic resonance spectroscopy, and X-ray diffraction are presented as structure elucidation tools for analytical chemistry of natural products. Discovering new molecular entities combined with dereplication of known organic compounds represent prerequisites for biological assays and for respective applications as pharmaceuticals or molecular markers. Liquid chromatography is briefly addressed with respect to its use in mass spectrometry- and nuclear magnetic resonance-based metabolomics studies.

New Cyclotetrapeptides and a New Diketopiperzine Derivative from the Marine Sponge-Associated Fungus Neosartorya glabra KUFA 0702

Two new cyclotetrapeptides, sartoryglabramides A (5) and B (6), and a new analog of fellutanine A (8) were isolated, together with six known compounds including ergosta-4, 6, 8 (14), 22-tetraen-3-one, ergosterol 5, 8-endoperoxide, helvolic acid, aszonalenin (1), (3R)-3-(1H-indol-3-ylmethyl)-3,4-dihydro-1H-1,4-benzodiazepine-2,5-dione (2), takakiamide (3), (11aR)-2,3-dihydro-1H-pyrrolo[2,1-c][1,4]benzodiazepine-5,11(10H,11aH)-dione (4), and fellutanine A (7), from the ethyl acetate extract of the culture of the marine sponge-associated fungus Neosartorya glabra KUFA 0702. The structures of the new compounds were established based on extensive 1D and 2D spectral analysis. X-ray analysis was also used to confirm the relative configuration of the amino acid constituents of sartoryglabramide A (5), and the absolute stereochemistry of the amino acid constituents of sartoryglabramide A (5) and sartoryglabramides B (6) was determined by chiral HPLC analysis of their hydrolysates by co-injection with the d- and l- amino acids standards. Compounds 1-8 were tested for their antibacterial activity against Gram-positive (Escherichia coli ATCC 25922) and Gram-negative (Staphyllococus aureus ATCC 25923) bacteria, as well as for their antifungal activity against filamentous (Aspergillus fumigatus ATCC 46645), dermatophyte (Trichophyton rubrum ATCC FF5) and yeast (Candida albicans ATCC 10231). None of the tested compounds exhibited either antibacterial (MIC > 256 μg/mL) or antifungal activities (MIC > 512 μg/mL).

New Polyketides and New Benzoic Acid Derivatives from the Marine Sponge-Associated Fungus Neosartorya quadricincta KUFA 0081

Two new pentaketides, including a new benzofuran-1-one derivative (1) and a new isochromen-1-one (5), and seven new benzoic acid derivatives, including two new benzopyran derivatives (2a, b), a new benzoxepine derivative (3), two new chromen-4-one derivatives (4b, 7) and two new benzofuran derivatives (6a, b), were isolated, together with the previously reported 2,3-dihydro-6-hydroxy-2,2-dimethyl-4H-1-benzopyran-4-one (4a), from the culture of the marine sponge-associated fungus Neosartorya quadricincta KUFA 0081. The structures of the new compounds were established based on 1D and 2D NMR spectral analysis, and in the case of compounds 1, 2a, 4b, 5, 6a and 7, the absolute configurations of their stereogenic carbons were determined by an X-ray crystallographic analysis. None of the isolated compounds were active in the tests for antibacterial activity against Gram-positive and Gram-negative bacteria, as well as multidrug-resistant isolates from the environment (MIC > 256 μg/mL), antifungal activity against yeast (Candida albicans ATTC 10231), filamentous fungus (Aspergillus fumigatus ATTC 46645) and dermatophyte (Trichophyton rubrum FF5) (MIC > 512 µg/mL) and in vitro growth inhibitory activity against the MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and A375-C5 (melanoma) cell lines (GI₅₀ > 150 µM) by the protein binding dye SRB method.

Extrolites of Aspergillus fumigatus and Other Pathogenic Species in Aspergillus Section Fumigati

Aspergillus fumigatus is an important opportunistic human pathogen known for its production of a large array of extrolites. Up to 63 species have been described in Aspergillus section Fumigati, some of which have also been reliably reported to be pathogenic, including A. felis, A. fischeri, A. fumigatiaffinis, A. fumisynnematus, A. hiratsukae, A. laciniosus, A. lentulus, A. novofumigatus, A. parafelis, A. pseudofelis, A. pseudoviridinutans, A. spinosus, A. thermomutatus, and A. udagawae. These species share the production of hydrophobins, melanins, and siderophores and ability to grow well at 37°C, but they only share some small molecule extrolites, that could be important factors in pathogenicity. According to the literature gliotoxin and other exometabolites can be contributing factors to pathogenicity, but these exometabolites are apparently not produced by all pathogenic species. It is our hypothesis that species unable to produce some of these metabolites can produce proxy-exometabolites that may serve the same function. We tabulate all exometabolites reported from species in Aspergillus section Fumigati and by comparing the profile of those extrolites, suggest that those producing many different kinds of exometabolites are potential opportunistic pathogens. The exometabolite data also suggest that the profile of exometabolites are highly specific and can be used for identification of these closely related species.