Spiromastixones A-O, antibacterial chlorodepsidones from a deep-sea-derived Spiromastix sp. fungus

Retrobisabolane A, a Novel Bisabolane-Derived Sesquiterpenoid Isolated from Deep-Sea-Derived Fungus Retroconis fusiformis MCCC 3A00792

One novel bisabolane-derived sesquiterpenoid retrobisabolane A (1), featuring a methyl group location at the C-4 position instead of C-3 in the bisabolanes, and a known ester-substituted eremophilane-type sesquiterpenoid cryptosphaerolide (2), along with three known indole alkaloids (3-5) were discovered from the fermented cultures of a deep-sea-derived fungus Retroconis fusiformis MCCC 3A00792. The planar structure of new compound 1 was determined by extensive analysis of the NMR and HRESIMS spectra. The relative and absolute configurations of 1 were resolved by the coupling constant (J), calculation of ECD and NMR spectra, and the DP4+ probability analysis of the 1H and 13C NMR data. Interestingly, retrobisabolane A was the new subclass of bisabolanes bearing a methyl group linkage at C-4 instead of C-3 position. Three human cancer cell lines (Hela, AGS, and BIU-87) were subjected to evaluate the cytotoxic activities of compounds 1-5. As a result, compound 2 exhibited significant inhibitory activities against three cell lines with IC50 values ranging from 9.95 to 18.77 μM.

Antibacterial properties of natural products from marine fungi reported between 2012 and 2023: a review

The oceans are rich in diverse microorganisms, animals, and plants. This vast biological complexity is a major source of unique secondary metabolites. In particular, marine fungi are a promising source of compounds with unique structures and potent antibacterial properties. Over the last decade, substantial progress has been made to identify these valuable antibacterial agents. This review summarizes the chemical structures and antibacterial activities of 223 compounds identified between 2012 and 2023. These compounds, effective against various bacteria including drug-resistant strains such as methicillin-resistant Staphylococcus aureus, exhibit strong potential as antibacterial therapeutics. The review also highlights the relevant challenges in transitioning from drug discovery to product commercialization. Emerging technologies such as metagenomics and synthetic biology are proposed as viable solutions. This paper sets the stage for further research on antibacterial compounds derived from marine fungi and advocates a multidisciplinary approach to combat drug-resistant bacteria.

Antibacterial insights into alternariol and its derivative alternariol monomethyl ether produced by a marine fungus

Alternaria alternata FB1 is a marine fungus identified as a candidate for plastic degradation in our previous study. This fungus has been recently shown to produce secondary metabolites with significant antimicrobial activity against various pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and the notorious aquaculture pathogen Vibrio anguillarum. The antibacterial compounds were purified and identified as alternariol (AOH) and its derivative, alternariol monomethyl ether (AME). We found that AOH and AME primarily inhibited pathogenic bacteria (MRSA or V. anguillarum) by disordering cell division and some other key physiological and biochemical processes. We further demonstrated that AOH could effectively inhibit the unwinding activity of MRSA topoisomerases, which are closely related to cell division and are the potential action target of AOH. The antibacterial activities of AOH and AME were verified by using zebrafish as the in vivo model. Notably, AOH and AME did not significantly affect the viability of normal human liver cells at concentrations that effectively inhibited MRSA or V. anguillarum. Finally, we developed the genetic operation system of A. alternata FB1 and blocked the biosynthesis of AME by knocking out omtI (encoding an O-methyl transferase), which facilitated A. alternata FB1 to only produce AOH. The development of this system in the marine fungus will accelerate the discovery of novel natural products and further bioactivity study.IMPORTANCEMore and more scientific reports indicate that alternariol (AOH) and its derivative alternariol monomethyl ether (AME) exhibit antibacterial activities. However, limited exploration of their detailed antibacterial mechanisms has been performed. In the present study, the antibacterial mechanisms of AOH and AME produced by the marine fungus Alternaria alternata FB1 were disclosed in vitro and in vivo. Given their low toxicity on the normal human liver cell line under the concentrations exhibiting significant antibacterial activity against different pathogens, AOH and AME are proposed to be good candidates for developing promising antibiotics against methicillin-resistant Staphylococcus aureus and Vibrio anguillarum. We also succeeded in blocking the biosynthesis of AME, which facilitated us to easily obtain pure AOH. Moreover, based on our previous results, A. alternata FB1 was shown to enable polyethylene degradation.

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.

Genome Mining and Biosynthetic Reconstitution of Fungal Depsidone Mollicellins Reveal a Dual Functional Cytochrome P450 for Ether Formation

Depsidones are significant in structural diversity and broad in biological activities; however, their biosynthetic pathways have not been well understood and have attracted considerable attention. Herein, we heterologously reconstituted a depsidone encoding gene cluster from Ovatospora sp. SCSIO SY280D in Aspergillus nidulans A1145, leading to production of mollicellins, a representative family of depsidones, and discovering a bifunctional P450 monooxygenase that catalyzes both ether formation and hydroxylation in the biosynthesis of the mollicellins. The functions of a decarboxylase and an aromatic prenyltransferase are also characterized to understand the tailoring modification steps. This work provides important insights into the biosynthesis of mollicellins.

Antimicrobial Polyketides from the Marine-Derived Fungus Spiromastix sp. SCSIO F190

Three diphenyl ethers (1-3) and a cyclopentenone (4), together with seven known compounds (5-11), were isolated from the fermentation broth of the marine sediment-derived fungus Spiromastix sp. SCSIO F190. Compounds 3 and 4 were found to exist as a pair of atropisomers (3a, 3b) and racemates (4a, 4b), respectively. The planar structures of compounds 1-4 were elucidated on the basis of NMR and HRESIMS data sets. The absolute configurations of 2 and 3 were determined by spectroscopic and single-crystal X-ray diffraction analyses, whereas the configuration of 4 was determined by spectroscopic and chiral analyses. All compounds, except for 4 and 11, displayed activities against various pathogenic bacteria. Notably, compounds 1-4, especially 1, exhibited strong activity against Gram-positive bacteria, including methicillin-resistant bacterial strains of Staphylococcus aureus (MRSA), Enterococcus faecalis ATCC 29212, and Bacillus subtilis BS01, with MIC values ranging from 0.5 to 4 μg/mL. Moreover, the structure-activity relationship analyses of the active compounds and their analogues revealed the critical structural features correlating to the observed antimicrobial activities, herein providing insights for antimicrobial drug development.

Filamentous fungi for sustainable vegan food production systems within a circular economy: Present status and future prospects

Filamentous fungi serve as potential candidates in the production of different value-added products. In the context of food, there are several advantages of using filamentous fungi for food. Among the main advantages is that the fungal biomass used food not only meets basic nutritional requirements but that it is also rich in protein, low in fat, and free of cholesterol. This speaks to the potential of filamentous fungi in the production of food that can substitute animal-derived protein sources such as meat. Moreover, life-cycle analyses and techno-economic analyses reveal that fungal proteins perform better than animal-derived proteins in terms of land use efficiency as well as global warming. The present article provides an overview of the potential of filamentous fungi as a source of food and food supplements. The commercialization potential as well as social, legal and safety issues of fungi-based food products are discussed.

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

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.

Bioactive secondary metabolites isolated from the Antarctic lichen Himantormia lugubris

Two new depsidones, himantormiones A and B ( 1 and 2 ) were isolated from the Antarctic lichen, Himantormia lugubris (Parmeliaceae), together with seven known compounds ( 3 - 9 ). The structures of the new compounds ( 1 and 2 ) were determined by means of spectroscopic analyses, including 1D and 2D NMR and HR-MS. The isolated compounds were evaluated for their antimicrobial and cytotoxic activities, where himantormione B ( 2 ) exhibited an inhibitory effect against Staphylococcus aureus with the IC 50 value of 7.01 ± 0.85 mM. Compound 2 also exhibited strong cytotoxic activity against HCT116 cells (colon cancer) with the EC 50 value of 1.11 ± 0.85 μM, where that of the positive control, 5-fluouracil, was 9.4 ± 1.90 μM.Two new depsidones, himantormiones A and B ( 1 and 2 ) were isolated from the Antarctic lichen, Himantormia lugubris (Parmeliaceae), together with seven known compounds ( 3 - 9 ). The structures of the new compounds ( 1 and 2 ) were determined by means of spectroscopic analyses, including 1D and 2D NMR and HR-MS. The isolated compounds were evaluated for their antimicrobial and cytotoxic activities, where himantormione B ( 2 ) exhibited an inhibitory effect against Staphylococcus aureus with the IC 50 value of 7.01 ± 0.85 mM. Compound 2 also exhibited strong cytotoxic activity against HCT116 cells (colon cancer) with the EC 50 value of 1.11 ± 0.85 μM, where that of the positive control, 5-fluouracil, was 9.4 ± 1.90 μM.

Antiviral Cyclopropane Acids from Deep-Sea-Derived Fungus Aspergillus sydowii

Four novel monocyclic cyclopropane acids, namely, sydocyclopropanes A–D (1–4), along with one known congener hamavellone B (5), were isolated from the Aspergillus sydowii MCCC 3A00324 fungus, which was isolated from the deep-sea sediment. The gross structures of novel compounds were established by detailed analyses of the spectroscopic data (HRESIMS and NMR spectra), and their absolute configurations were resolved on the basis of the quantum chemical calculations of ECD and NMR data, in association with DP4+ probability analyses. Sydocyclopropanes A–D, featuring the 1,1,2,3-tetrasubstituted cyclopropane nucleus with different lengthy alkyl side chains, were discovered in nature for the first time. All compounds exhibited antiviral activities against A/WSN/33 (H1N1), with IC₅₀ values ranging from 26.7 to 77.2 μM, of which compound 1 exhibited a moderate inhibitory effect (IC₅₀ = 26.7 μM).

Rhizosphere 16S-ITS Metabarcoding Profiles in Banana Crops Are Affected by Nematodes, Cultivation, and Local Climatic Variations

Agriculture affects soil and root microbial communities. However, detailed knowledge is needed on the effects of cropping on rhizosphere, including biological control agents (BCA) of nematodes. A metabarcoding study was carried out on the microbiota associated with plant parasitic and other nematode functional groups present in banana farms in Tenerife (Canary Islands, Spain). Samples included rhizosphere soil from cv Pequeña Enana or Gruesa and controls collected from adjacent sites, with the same agroecological conditions, without banana roots. To characterize the bacterial communities, the V3 and V4 variable regions of the 16S rRNA ribosomal gene were amplified, whereas the internal transcribed spacer (ITS) region was used for the fungi present in the same samples. Libraries were sequenced with an Illumina MiSeq™ in paired ends with a 300-bp read length. For each sample, plant parasitic nematodes (PPN) and other nematodes were extracted from the soil, counted, and identified. Phytoparasitic nematodes were mostly found in banana rhizosphere. They included Pratylenchus goodeyi, present in northern farms, and Helicotylenchus spp., including H. multicinctus, found in both northern and southern farms. Metabarcoding data showed a direct effect of cropping on microbial communities, and latitude-related factors that separated northern and southern controls from banana rizosphere samples. Several fungal taxa known as nematode BCA were identified, with endophytes, mycorrhizal species, and obligate Rozellomycota endoparasites, almost only present in the banana samples. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Planctomycetes, Bacteroidetes, Chloroflexi, and Acidobacteria. The ITS data showed several operational taxonomic units (OTUs) belonging to Sordariomycetes, including biocontrol agents, such as Beauveria spp., Arthrobotrys spp., Pochonia chlamydosporia, and Metarhizium anisopliae. Other taxa included Trichoderma harzianum, Trichoderma longibrachiatum, Trichoderma virens, and Fusarium spp., together with mycoparasites such as Acrostalagmus luteoalbus. However, only one Dactylella spp. showed a correlation with predatory nematodes. Differences among the nematode guilds were found, as phytoparasitic, free-living, and predatory nematode groups were correlated with specific subsets of other bacteria and fungi. Crop cultivation method and soil texture showed differences in taxa representations when considering other farm and soil variables. The data showed changes in the rhizosphere and soil microbiota related to trophic specialization and specific adaptations, affecting decomposers, beneficial endophytes, mycorrhizae, or BCA, and plant pathogens.

Antimicrobial Properties and the Effect of Temperature on the Formation of Secondary Metabolites in Psychrophilic Micromycetes

Abstract

The ability of representatives of psychrotolerant micromycetes to produce antimicrobial compounds was studied. A promising producer of antibiotics, Penicillium vulpinum KPB F-290, was selected (from 98 cultures) as a result of the screening. The producer was active against opportunistic fungi and bacteria. The isolated active fractions can be attributed to the group of antimicrobial compounds, including ß-lactam antibiotics and peptides.

Halogenation in Fungi: What Do We Know and What Remains to Be Discovered?

In nature, living organisms produce a wide variety of specialized metabolites to perform many biological functions. Among these specialized metabolites, some carry halogen atoms on their structure, which can modify their chemical characteristics. Research into this type of molecule has focused on how organisms incorporate these atoms into specialized metabolites. Several families of enzymes have been described gathering metalloenzymes, flavoproteins, or S-adenosyl-L-methionine (SAM) enzymes that can incorporate these atoms into different types of chemical structures. However, even though the first halogenation enzyme was discovered in a fungus, this clade is still lagging behind other clades such as bacteria, where many enzymes have been discovered. This review will therefore focus on all halogenation enzymes that have been described in fungi and their associated metabolites by searching for proteins available in databases, but also by using all the available fungal genomes. In the second part of the review, the chemical diversity of halogenated molecules found in fungi will be discussed. This will allow the highlighting of halogenation mechanisms that are still unknown today, therefore, highlighting potentially new unknown halogenation enzymes.

Discovery of Anti-MRSA Secondary Metabolites from a Marine-Derived Fungus Aspergillus fumigatus

Methicillin-resistant Staphylococcus aureus (MRSA), a WHO high-priority pathogen that can cause great harm to living beings, is a primary cause of death from antibiotic-resistant infections. In the present study, six new compounds, including fumindoline A-C (1-3), 12β, 13β-hydroxy-asperfumigatin (4), 2-epi-tryptoquivaline F (17) and penibenzophenone E (37), and thirty-nine known ones were isolated from the marine-derived fungus Aspergillus fumigatus H22. The structures and the absolute configurations of the new compounds were unambiguously assigned by spectroscopic data, mass spectrometry (MS), electronic circular dichroism (ECD) spectroscopic analyses, quantum NMR and ECD calculations, and chemical derivatizations. Bioactivity screening indicated that nearly half of the compounds exhibit antibacterial activity, especially compounds 8 and 11, and 33-38 showed excellent antimicrobial activities against MRSA, with minimum inhibitory concentration (MIC) values ranging from 1.25 to 2.5 μM. In addition, compound 8 showed moderate inhibitory activity against Mycobacterium bovis (MIC: 25 μM), compound 10 showed moderate inhibitory activity against Candida albicans (MIC: 50 μM), and compound 13 showed strong inhibitory activity against the hatching of a Caenorhabditis elegans egg (IC50: 2.5 μM).

Metabolic Potential of Halophilic Filamentous Fungi—Current Perspective

Salty environments are widely known to be inhospitable to most microorganisms. For centuries salt has been used as a food preservative, while highly saline environments were considered uninhabited by organisms, and if habited, only by prokaryotic ones. Nowadays, we know that filamentous fungi are widespread in many saline habitats very often characterized also by other extremes, for example, very low or high temperature, lack of light, high pressure, or low water activity. However, fungi are still the least understood organisms among halophiles, even though they have been shown to counteract these unfavorable conditions by producing multiple secondary metabolites with interesting properties or unique biomolecules as one of their survival strategies. In this review, we focused on biomolecules obtained from halophilic filamentous fungi such as enzymes, pigments, biosurfactants, and osmoprotectants.

Chlorinated metabolites with antibacterial activities from a deep-sea-derived Spiromastix fungus

Chromatographic separation of the solid cultures of a deep-sea-derived Spiromastix fungus (MCCC 3A00308) resulted in the isolation of eight compounds. Their structures were identified on the basis of the spectroscopic data. Compounds 1–8 are classified as depsidone-type (1–4), isocoumarin-type (5 and 6), and benzothiazole-type (7 and 8), of which 1–7 are new compounds and 1–3 along with 5 and 6 are chlorinated. Compound 3 is characterized by trichlorination and shows potent activities against Gram-positive pathogenic bacteria including Staphylococcus aureus ATCC 25923, Bacillus thuringiensis ATCC 10792, and Bacillus subtilis CMCC 63501, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 1.0 μg mL⁻¹. This study extends the chemical diversity of chlorinated natural products from marine-derived fungi and provides a promising lead for the development of antibacterial agents.

Chromatographic separation of the solid cultures of a deep-sea-derived Spiromastix fungus (MCCC 3A00308) resulted in the isolation of five chlorinated compounds with antibacterial activities.

Epigenetic Manipulation to Trigger Production of Guaiane-Type Sesquiterpenes from a Marine-Derived Spiromastix sp. Fungus with Antineuroinflammatory Effects

Epigenetic manipulation of a deep-sea sediment-derived Spiromastix sp. fungus using suberoylanilide hydroxamic acid (SAHA) induction resulted in the activation of a terpene-related biosynthetic gene cluster, and nine new guaiane-type sesquiterpenes, spiromaterpenes A-I (1-9), were isolated. Their structures were determined using various spectroscopic techniques, in association with the modified Mosher's method, computed electronic circular dichroism (ECD) spectra, and chemical conversion for configurational assignments. Compounds 4-6 exhibited significant effects against the NO production on lipopolysaccharide (LPS)-induced microglia cells BV2, and the preliminary SAR analyses demonstrated that a 2(R),11-diol unit is favorable. The most active 5 abolished LPS-induced NF-κB translocation from the cytosol to the nucleus in BV-2 microglial cells, accompanied by the marked reduction of the transcription levels of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α dose-dependently in both LPS-induced BV-2 and BV-2 cells, as well as the protein and mRNA levels of iNOS and COX-2. This study complements the gap in knowledge regarding the anti-neuroinflammatory activity of guaiane-type sesquiterpenoids at the cellular level and suggests that 5 is promising for further optimization as a multifunctional agent for antineuroinflammation.

Biologically Active Antimicrobial Compounds from Marine Microorganisms (2005-2019)

INTRODUCTION

The increase in contagious diseases like nosocomial infections, urinary tract infections, and meningitis has led to the emergence of antimicrobial resistance urgently needs new antimicrobial medication with new modes of action. Some of the antibiotics present in the market have been obtained from terrestrial plants, or extracted semisynthetically from materials which can be fermented.

METHODS

Marine microorganisms account for approximately 80% of sea biomass. They are essential for the survival and well-being of aquatic habitats due to their indispensable contribution to biogeochemical cycles and biological processes. In marine ecosystems, microorganisms live as microbial communities in seawater, where symbiotic relationships are formed, and their ecological functions are fulfilled.

RESULTS

Marine microorganisms remain the largest, most diverse and most exciting source of structurally and functionally complex antimicrobial agents. They are extremely involved in their structure and functions. Enormous biological wealth lies in marine habitats. These microorganisms are potential sources of novel antimicrobial compounds to combat the most infectious diseases like nosocomial infections, and urinary tract infections.

CONCLUSION

This study deals with biologically active antimicrobial compounds taken from marine microorganism source, which was reported between the years 2005 and 2019. This review highlights their chemical groups, their bioactivities and sources. Marine microorganism exploitation techniques have also been reported by the authors.

Biosynthetic versatility of marine-derived fungi on the delivery of novel antibacterial agents against priority pathogens

Despite the increasing number of novel marine natural products being reported from fungi in the last three decades, to date only the broad-spectrum cephalosporin C can be tracked back as marine fungal-derived drug. Cephalosporins were isolated in the early 1940s from a strain of Acremonium chrysogenum obtained in a sample collected in sewage water in the Sardinian coast, preliminary findings allowing the discovery of cephalosporin C. Since then, bioprospection of marine fungi has been enabling the identification of several metabolites with antibacterial effects, many of which proving to be active against multi-drug resistant strains, available data suggesting also that some might fuel the pharmaceutical firepower towards some of the bacterial pathogens classified as a priority by the World Health Organization. Considering the success of their terrestrial counterparts on the discovery and development of several antibiotics that are nowadays used in the clinical setting, marine fungi obviously come into mind as producers of new prototypes to counteract antibiotic-resistant bacteria that are no longer responding to available treatments. We mainly aim to provide a snapshot on those metabolites that are likely to proceed to advanced preclinical development, not only based on their antibacterial potency, but also considering their targets and modes of action, and activity against priority pathogens.

Acremolin D, a new acremolin alkaloid from the deep-sea sediment derived Aspergillus sydowii fungus

Chemical investigation of the deep-sea-derived fungus Aspergillus sydowii MCCC 3A00324 led to the isolation of one new acremolin type alkaloid (acremolin D, 1) and five known alkaloids (2‒6). The planar structure of 1 was established by the extensive analyses of the NMR and HRESIMS data, while its absolute configuration was assigned by the comparison of the experimental and calculated ECD data. Acremolin D (1) represented the second analogue of acremolin found in nature. All compounds were evaluated for their cytotoxic activities against six human cancer cell lines (A549, Hela-S3, MCF-7, HepG2, K562, and SF-268). As a result, compounds 1 and 2 exhibited a certain inhibitory effects against the proliferation of the A549, Hela-S3, HepG2, and K562 cell lines at the concentration of 20 µM.

Analysis of Soil Fungal and Bacterial Communities in Tianchi Volcano Crater, Northeast China

High-altitude volcanoes, typical examples of extreme environments, are considered of particular interest in biology as a possible source of novel and exclusive microorganisms. We analyzed the crater soil microbial diversity of Tianchi Volcano, northeast China, by combining molecular and morphological analyses of culturable microbes, and metabarcoding based on Illumina sequencing, in order to increase our understanding of high-altitude volcanic microbial community structure. One-hundred and seventeen fungal strains belonging to 51 species and 31 genera of Ascomycota, Basidiomycota and Mucoromycota were isolated. Penicillium, Trichoderma, Cladosporium, Didymella, Alternaria and Fusarium dominated the culturable fungal community. A considerable number of isolated microbes, including filamentous fungi, such as Aureobasidium pullulans and Epicoccum nigrum, yeasts (Leucosporidium creatinivorum), and bacteria (Chryseobacterium lactis and Rhodococcus spp.), typical of high-altitude, cold, and geothermal extreme environments, provided new insights in the ecological characterization of the investigated environment, and may represent a precious source for the isolation of new bioactive compounds. A total of 1254 fungal and 2988 bacterial operational taxonomic units were generated from metabarcoding. Data analyses suggested that the fungal community could be more sensitive to environmental and geographical change compared to the bacterial community, whose network was characterized by more complicated and closer associations.

Mollicellins S-U, three new depsidones from Chaetomium brasiliense SD-596 with anti-MRSA activities

Fungi are important resources for drug development, as they have a diversity of genes, that can produce novel secondary metabolites with effective bioactivities. Here, five depsidone-based analogs were isolated from the rice media of Chaetomium brasiliense SD-596. Their structures were elucidated using NMR and mass spectrometry analysis. Five compounds, including three new depsidone analogs, mollicellin S (1), mollicellin T (2), and mollicellin U (3), and two known compounds, mollicellin D (4) and mollicellin H (5), exhibited significant inhibition against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), with MIC values ranging from 6.25 to 12.5 μg ml^-1. Herein, we identified the predicted plausible biosynthetic cluster of the compounds and discussed the structure-activity relationship. Finally, we found that the introduction of aldehyde and methoxyl groups provide marked improvement for the inhibition against MRSA.

A Review: Halogenated Compounds from Marine Fungi

Marine fungi produce many halogenated metabolites with a variety of structures, from acyclic entities with a simple linear chain to multifaceted polycyclic molecules. Over the past few decades, their pharmaceutical and medical application have been explored and still the door is kept open due to the need of new drugs from relatively underexplored sources. Biological properties of halogenated compounds such as anticancer, antiviral, antibacterial, anti-inflammatory, antifungal, antifouling, and insecticidal activity have been investigated. This review describes the chemical structures and biological activities of 217 halogenated compounds derived mainly from Penicillium and Aspergillus marine fungal strains reported from 1994 to 2019.

New Monoterpenoids and Polyketides from the Deep-Sea Sediment-Derived Fungus Aspergillus sydowii MCCC 3A00324

Chemical study of the secondary metabolites of a deep-sea-derived fungus Aspergillus sydowii MCCC 3A00324 led to the isolation of eleven compounds (1-11), including one novel (1) and one new (2) osmane-related monoterpenoids and two undescribed polyketides (3 and 4). The structures of the metabolites were determined by comprehensive analyses of the NMR and HRESIMS spectra, in association with quantum chemical calculations of the 13C NMR, ECD, and specific rotation data for the configurational assignment. Compound 1 possessed a novel monoterpenoid skeleton, biogenetically probably derived from the osmane-type monoperpenoid after the cyclopentane ring cleavage and oxidation reactions. Additionally, compound 3 was the first example of the α-pyrone derivatives bearing two phenyl units at C-3 and C-5, respectively. The anti-inflammatory activities of 1-11 were tested. As a result, compound 6 showed potent inhibitory nitric oxide production in lipopolysaccharide (LPS)-activated BV-2 microglia cells with an inhibition rate of 94.4% at the concentration of 10 µM. In addition, a plausible biosynthetic pathway for 1 and 2 was also proposed.

A New Depsidone from Teloschistes flavicans and the Antileukemic Activity

Lichens produce a variety of secondary metabolites that could be potential sources of pharmaceutically useful chemicals. However, only a limited number of lichen metabolites have been investigated for their biological significance. The objective of this study was to identify the potential compounds responsible for the antileukemic activity of lichen Teloschistes flavicans. Among three fractions (n-hexane, EtOAc, and MeOH-H₂O), the ethyl acetate (EtOAc) fraction of T. flavicans methanolic extract showed the strongest inhibition in the HL-60 cell line. Additionally, the EtOAc fraction was further purified to obtain a new depsidone, 2,7-dichloro-3,8-dimethoxy-1,6,9-trimethyl-11H-dibenzo[b,e][1,4]dioxepin-11-one, named as flavicansone, along with rhizonic acid, parietin, and vicanicin. Flavicansone demonstrated the most significant inhibitory action against cell proliferation among the four isolated compounds.

A new depsidone derivative from mangrove endophytic fungus Aspergillus sp. GXNU-A9

A new tetracyclic depsidone derivative, guanxidone A (1), together with three known metabolites 2-4, was isolated from the mangrove endophytic fungus Aspergillus sp. GXNU-A9. The structure of compound 1 was established by HR-ESI-MS, 1 D and 2 D NMR data, as well as by comparison with literature data. Compounds 1-4 were evaluated for their anti-inflammatory effects on the production of the nitric oxide (NO), and compound 1 significantly reduced the production of NO in lipopolysaccharide (LPS)-stimulated cells with IC₅₀ value of 8.22 µM.

Molecules derived from the extremes of life: a decade later

Covering: Early 2008 until the end of 2019Microorganisms which survive (extreme-tolerant) or even prefer (extremophilic) living at the limits of pH, temperature, salinity and pressure found on earth have proven to be a rich source of novel structures. In this update we summarise the wide variety of new molecules which have been isolated from extremophilic and extreme-tolerant microorganisms since our original 2009 review, highlighting the range of bioactivities these molecules have been reported to possess.

Marine Pharmacology in 2014-2015: Marine Compounds with Antibacterial, Antidiabetic, Antifungal, Anti-Inflammatory, Antiprotozoal, Antituberculosis, Antiviral, and Anthelmintic Activities; Affecting the Immune and Nervous Systems, and Other Miscellaneous Mechanisms of Action

The systematic review of the marine pharmacology literature from 2014 to 2015 was completed in a manner consistent with the 1998-2013 reviews of this series. Research in marine pharmacology during 2014-2015, which was reported by investigators in 43 countries, described novel findings on the preclinical pharmacology of 301 marine compounds. These observations included antibacterial, antifungal, antiprotozoal, antituberculosis, antiviral, and anthelmintic pharmacological activities for 133 marine natural products, 85 marine compounds with antidiabetic, and anti-inflammatory activities, as well as those that affected the immune and nervous system, and 83 marine compounds that displayed miscellaneous mechanisms of action, and may probably contribute to novel pharmacological classes upon further research. Thus, in 2014-2015, the preclinical marine natural product pharmacology pipeline provided novel pharmacology as well as new lead compounds for the clinical marine pharmaceutical pipeline, and thus continued to contribute to ongoing global research for alternative therapeutic approaches to many disease categories.

Curdepsidones B⁻G, Six Depsidones with Anti-Inflammatory Activities from the Marine-Derived Fungus Curvularia sp. IFB-Z10

Six new depsidones, curdepsidones B-G (1-6), were obtained from the marine-derived fungus Curvularia sp. IFB-Z10. Their planar structures were determined by comprehensive analysis of HRESIMS and 1D/2D-NMR data. The absolute configuration of curdepsidones B-C (1-2) were established by synergistic use of DFT/NMR (density functional theory/nuclear magnetic resonance) and TDDFT/ECD (time-dependent density functional theory/electronic circular dichroism) calculations. Partial isolated compounds were tested for their anti-inflammatory activities in Propionibacterium acnes-induced THP-1 cells. Curdepsidone C (2) displayed significant anti-inflammatory properties with an IC50 value of 7.47 ± 0.35 μM, and reduced the P. acnes-induced phosphorylation levels of JNK and ERK in a dose-dependent mechanism. The possible anti-inflammatory mechanism of 2 was also investigated by molecular docking.

A Computer-Driven Approach to Discover Natural Product Leads for Methicillin-Resistant Staphylococcus aureus Infection Therapy

The risk of methicillin-resistant Staphylococcus aureus (MRSA) infection is increasing in both the developed and developing countries. New approaches to overcome this problem are in need. A ligand-based strategy to discover new inhibiting agents against MRSA infection was built through exploration of machine learning techniques. This strategy is based in two quantitative structure–activity relationship (QSAR) studies, one using molecular descriptors (approach A) and the other using descriptors (approach B). In the approach A, regression models were developed using a total of 6645 molecules that were extracted from the ChEMBL, PubChem and ZINC databases, and recent literature. The performance of the regression models was successfully evaluated by internal and external validation, the best model achieved R² of 0.68 and RMSE of 0.59 for the test set. In general natural product (NP) drug discovery is a time-consuming process and several strategies for dereplication have been developed to overcome this inherent limitation. In the approach B, we developed a new NP drug discovery methodology that consists in frontloading samples with 1D NMR descriptors to predict compounds with antibacterial activity prior to bioactivity screening for NPs discovery. The NMR QSAR classification models were built using 1D NMR data (¹H and ¹³C) as descriptors, from crude extracts, fractions and pure compounds obtained from actinobacteria isolated from marine sediments collected off the Madeira Archipelago. The overall predictability accuracies of the best model exceeded 77% for both training and test sets.

Hansforesters A-M, polyesters from the sponge-associated fungus Hansfordia sinuosae with antibacterial activities

Bioassay-guided fractionation and chromatographic separation of a sponge-derived fungus Hansfordia sinuosae, resulted in the isolation of thirteen new polyesters namely hansforesters A-M (1-13), along with five known analogues involving ascotrichalactone A, ascotrichester B, 15G256π, 6R-hydroxymellein, and (-)orthosporin. The structures of the new compounds were determined through extensive spectroscopic analysis, in addition to the chemical conversion for the configurational assignment. The polyesters incorporating the motifs of orsellinic acid, 2,4-dihydroxy-6-acetonylbenzoic acid, and orcinotriol were found from nature for the first time. Hansforester A (1) and ascotrichalactone A exhibited potent inhibition against a panel of bacterial strains, including the agricultural pathogenic bacteria, Pseudomonas lachrymans, Agrobacterium tumefaciens, Xanthomonas vesicatoria, and Ralstonia solanacearum, with the MIC values of 15.6 μM, and the human infected bacterium Staphylococcus aureus with the MIC values of 3.9 μM. These findings suggested that hansforester A and ascotrichalactone A are the potential leads to be developed as the antibacterial agents for the treatment of agriculture bacterial pathogens.

Antibiotics from Deep-Sea Microorganisms: Current Discoveries and Perspectives

The increasing emergence of new forms of multidrug resistance among human pathogenic bacteria, coupled with the consequent increase of infectious diseases, urgently requires the discovery and development of novel antimicrobial drugs with new modes of action. Most of the antibiotics currently available on the market were obtained from terrestrial organisms or derived semisynthetically from fermentation products. The isolation of microorganisms from previously unexplored habitats may lead to the discovery of lead structures with antibiotic activity. The deep-sea environment is a unique habitat, and deep-sea microorganisms, because of their adaptation to this extreme environment, have the potential to produce novel secondary metabolites with potent biological activities. This review covers novel antibiotics isolated from deep-sea microorganisms. The chemical classes of the compounds, their bioactivities, and the sources of organisms are outlined. Furthermore, the authors report recent advances in techniques and strategies for the exploitation of deep-sea microorganisms.

Biologically active fungal depsidones: Chemistry, biosynthesis, structural characterization, and bioactivities

Fungi produce a wide range of structurally unique metabolites. Depsidones represent one of the most interesting classes of metabolites, consisting of two 2,4-dihydroxybenzoic acid rings linked together by both ether and ester bonds. Naturally occurring depsidones are produced by lichen, fungi, and plants. They possessed a wide array of bioactivities, including antioxidant, antiproliferative, antimalarial, cytotoxic, antibacterial, radical scavenging, antihypertensive, anti-inflammatory, antifungal, and aromatase and protein kinase inhibitory. In order to point out the potential of this class of compounds, the present review focuses only on the depsidones that have been isolated from fungal source and published from 1978 to 2018. This review outlined the research on the biosynthesis, source, isolation, spectral and physical data, and bioactivities of the naturally occurring fungal depsidones. On the basis of 88 references, > 80 compounds have been described.

Fungal Metabolite Antagonists of Plant Pests and Human Pathogens: Structure-Activity Relationship Studies

Fungi are able to produce many bioactive secondary metabolites that belong to different classes of natural compounds. Some of these compounds have been selected for their antagonism against pests and human pathogens and structure-activity relationship (SAR) studies have been performed to better understand which structural features are essential for the biological activity. In some cases, these studies allowed for the obtaining of hemisynthetic derivatives with increased selectivity and stability in respect to the natural products as well as reduced toxicity in view of their potential practical applications. This review deals with the SAR studies performed on fungal metabolites with potential fungicidal, bactericidal, insecticidal, and herbicidal activities from 1990 to the present (beginning of 2018).

Depsidones and an α-pyrone derivative from Simplicillium sp. PSU-H41, an endophytic fungus from Hevea brasiliensis leaf [corrected]

Nine previously undescribed depsidones (simplicildones A-I) and one previously undescribed α-pyrone (simplicilopyrone) were isolated from the endophytic fungus Simplicillium sp. PSU-H41 along with 11 known compounds. Their structures were established by extensive spectroscopic analysis. Simplicildone A and known botryorhodine C displayed weak antibacterial against Staphylococcus aureus with equal MIC values of 32 μg/mL. Additionally, botryorhodine C was active against methicillin-resistant S. aureus with the same MIC value. Simplicildone C exhibited weak antifungal activity against Cryptococcus neoformans with an MIC value of 32 μg/mL. In addition, simplicildones A and C and botryorhodine C were noncytotoxic against noncancerous Vero cells.

Spirograterpene A, a Tetracyclic Spiro-Diterpene with a Fused 5/5/5/5 Ring System from the Deep-Sea-Derived Fungus Penicillium granulatum MCCC 3A00475

A novel spiro-tetracyclic diterpene, spirograterpene A (1), was isolated from the deep-sea-derived fungus Penicillium granulatum MCCC 3A00475, together with two biosynthetically related cyclopianes, conidiogenone I (2) and conidiogenone C (3). The relative configuration of 1 was elucidated by extensive spectroscopic analyses, and the absolute structure was established by the modified Mosher's method. Compound 1 is the second example of a diterpene featuring a 5/5/5/5 spirocyclic carbon skeleton. It showed modest antiallergic activity.

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.

Penicilones A-D, Anti-MRSA Azaphilones from the Marine-Derived Fungus Penicillium janthinellum HK1-6

Four new azaphilones, penicilones A-D (1-4), were isolated from the mangrove rhizosphere soil-derived fungus Penicillium janthinellum HK1-6. Their planar structures and absolute configurations were determined by extensive analysis of NMR spectroscopic data, ECD spectra, the modified Mosher's method, and chemical conversions. Interestingly, 1 and 2 had the opposite configuration at C-7 compared to the closely related chloro analogues 3 and 4. Ester hydrolysis of 2 and 4 afforded their parental azaphilones, named penicilones E (5) and F (6). Compounds 1-6 were evaluated for their antibacterial activities in vitro. Penicilones B-D (2-4) showed potent anti-MRSA (Staphylococcus aureus ATCC 43300, ATCC 33591) activities with MIC values ranging from 3.13 to 6.25 μg/mL.

Cold-water marine natural products, 2006 to 2016

This is an update report on marine natural products isolated from cold-water organisms in the last decade, following the previous review that covered the literature up to 2005. Emphasis is on structural assignments and biological activity.