Phylogenetic diversity and antibacterial activity of culturable fungi derived from the zoanthid Palythoa haddoni in the South China Sea

Integrating Activity-Guided Strategy and Fingerprint Analysis to Target Potent Cytotoxic Brefeldin A from a Fungal Library of the Medicinal Mangrove Acanthus ilicifolius

Mangrove-associated fungi are rich sources of novel and bioactive compounds. A total of 102 fungal strains were isolated from the medicinal mangrove Acanthus ilicifolius collected from the South China Sea. Eighty-four independent culturable isolates were identified using a combination of morphological characteristics and internal transcribed spacer (ITS) sequence analyses, of which thirty-seven strains were selected for phylogenetic analysis. The identified fungi belonged to 22 genera within seven taxonomic orders of one phyla, of which four genera Verticillium, Neocosmospora, Valsa, and Pyrenochaeta were first isolated from mangroves. The cytotoxic activity of organic extracts from 55 identified fungi was evaluated against human lung cancer cell lines (A-549), human cervical carcinoma cell lines (HeLa), human hepatoma cells (HepG2), and human acute lymphoblastic leukemia cell lines (Jurkat). The crude extracts of 31 fungi (56.4%) displayed strong cytotoxicity at the concentration of 50 μg/mL. Furthermore, the fungus Penicillium sp. (HS-N-27) still showed strong cytotoxic activity at the concentration of 25 µg/mL. Integrating cytotoxic activity-guided strategy and fingerprint analysis, a well-known natural Golgi-disruptor and Arf-GEFs inhibitor, brefeldin A, was isolated from the target active strain HS-N-27. It displayed potential activity against A549, HeLa and HepG2 cell lines with the IC50 values of 101.2, 171.9 and 239.1 nM, respectively. Therefore, combining activity-guided strategy with fingerprint analysis as a discovery tool will be implemented as a systematic strategy for quick discovery of active compounds.

Phylogenetic Diversity, Antimicrobial and Antioxidant Potential and Identification of Bioactive Compounds from Culturable Endophytic Fungi Associated with Mangrove Bruguiera sexangula (Lour.) Poir

A total of 96 isolates were obtained from 375 segments, isolated from the healthy roots, stems, leaves, hypocotyls and flowers of Bruguiera sexangula (Lour.) Poir. collected at the Dong Zhai Gang Mangrove Garden on Hainan Island, and 20 independent representative isolates were identified using a combination of morphological and molecular approaches. The most frequent endophytic fungal species isolated were Diaporthe phaseolorum (relative frequency = 31.2%). The Shannon-Wiener diversity and Simpson's diversity index both showed that stems possessed the highest diversity compared to the other tissues estimated. Ethyl acetate extracts and the isolated metabolites were tested for antimicrobial activity using the serial dilution technique and for antioxidant activity using 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonicacid) (ABTS) radical-scavenging capacity assays, respectively. The fungal isolate HL18 (Gelasinospora endodonta) cultured on Czapek's agar (CA) displayed a broad spectrum of antimicrobial activities and was significantly active against Escherichia coli (MIC = 0.0625 mg ml^-1). Antioxidant assays showed that most of the fungal isolates (60.0%) exhibited some degree of antioxidant capacity (%RSA > 50%). The stain HL14 (Pestalotiopsis mangiferae) grown on potato dextrose agar (PDA) exhibited the highest DPPH and ABTS radical-scavenging capability with IC₅₀ values of 0.717 ± 0.012 mg ml^-1 and 0.787 ± 0.027 mg ml^-1, respectively. Furthermore, five known secondary metabolites 1-5 were isolated and identified from HL-14. Compounds 1 and 5 exhibited weak antioxidant activity.

Diversity of filamentous fungi associated with coral and sponges in coastal reefs of northeast Brazil

Fungi are known to form associations with various marine organisms and substrata such as sponges and corals, both as potential symbionts or pathogens. These microorganisms occupy an ecological niche that has recently attracted great attention due to their potential in either ecological or pharmaceutical advances. However, the interaction between marine invertebrates and fungi is still poorly understood, including how they are affected by anthropogenic actions. Here, we identified 89 fungal isolates through sequencing of the ITS rDNA region obtained from the various sponge and coral species collected at two northeast Brazilian reefs. We found 43 species of fungi from 16 genera, all belonging to phylum Ascomycota. The sponges and coral shared four genera: Aspergillus, Penicillium, Trichoderma, and Cladosporium, all commonly found in terrestrial habitats and associated with marine invertebrates. We observed some unusual species in relation to the marine environment, such as Clonostachys rosea and Neopestalotiopsis clavispora, most of them related to plants, either as saprophytic or pathogenic, suggesting that these species were transported from the surrounding terrestrial environment to the reefs. In addition, some isolates represent possible undescribed species, reinforcing the importance of studying the marine environment in relation to its ecological and biotechnological importance.

Sordarin Diterpene Glycosides with an Unusual 1,3-Dioxolan-4-one Ring from the Zoanthid-Derived Fungus Curvularia hawaiiensis TA26-15

Six new sordarin tetracyclic diterpene glycosides, moriniafungins B-G (1-6), and a new sordaricin tetracyclic diterpene, sordaricin B (8), together with two known analogues, moriniafungin (7) and sordaricin (9), were isolated from the zoanthid-derived fungus Curvularia hawaiiensis TA26-15. The structures of the new compounds were elucidated by comprehensive analyses of spectroscopic data, including 1D and 2D NMR and MS data. Compounds 1-6 represent the first case of sordarins from marine-derived fungi possessing a sordarose with a spiro 1,3-dioxolan-4-one ring, which is rare in the nature. Compound 4 showed antifungal activity against Candida albicans ATCC10231 with an MIC value of 2.9 μM.

Microalgal Microscale Model for Microalgal Growth Inhibition Evaluation of Marine Natural Products

Marine organisms especially sessile invertebrates, such as soft corals, gorgonians and sponges, can survive in the competitive environment mainly relying on their second metabolites with chemoecological effects including allelopathy and algal growth inhibition. It is well known that the microscale models are urgently needed in marine chemoecology assessment to evaluate the algal growth inhibition activity of trace quantity natural products. In this work, a microalgal growth inhibition model was established for microalgal inhibition evaluation of marine natural products with 96-well microplate by automatic fluorescence observation using microplate reader. Subsequently, this model was applied to bioassay-guided isolation and preliminary bioactivity screening of the secondary metabolites from soft corals, gorgonians, sponges and their symbiotic microbes collected from the South China Sea. As a result, fifteen compounds (1‒15) were found to exhibit microalgal growth inhibition activities against at least one of marine microalgae, Karenia mikimotoi, Isochrysis galbana, and Heterosigma akashiwo. Specifically, altersolanol C (13) demonstrated potent activity against K. mikimotoi with the 96h-EC₅₀ value of 1.16 µg/mL, more than four times stronger than that of the positive control K₂Cr₂O₇. It was suggested that the microalgal growth inhibition microscale model is suitable for bioassay-guided isolation and preliminary bioactivity screening of marine natural products.

Anti-Phytopathogenic and Cytotoxic Activities of Crude Extracts and Secondary Metabolites of Marine-Derived Fungi

Thirty-one isolates belonging to eight genera in seven orders were identified from 141 strains that were isolated from several marine plants. Alternaria sp. and Fusarium sp. were found to be the predominant fungi. Evaluation of the anti-phytopathogenic bacterial and fungal activities, as well as the cytotoxicity of these 31 extracts, revealed that most of them displayed different levels of bioactivities. Due to their interesting bioactivities, two fungal strains—Fusarium equiseti (P18) and Alternaria sp. (P8)—were selected for chemical investigation and compounds 1–4 were obtained. The structure of 1 was elucidated by 1D and 2D NMR analysis, as well as high-resolution electrospray ionization mass spectroscopy (HRESIMS), and the absolute configuration of its stereogenic carbon (C-11) was established by comparison of the experimental and calculated electronic circular-dichroism (ECD) spectra. Moreover, alterperylenol (4) exhibited antibacterial activity against Clavibacter michiganensis with a minimum inhibitory concentration (MIC) of 1.95 μg/mL, which was 2-fold stronger than that of streptomycin sulfate. Additionally, an antibacterial mechanism study revealed that 4 caused membrane hyperpolarization without evidence of destruction of cell membrane integrity. Furthermore, stemphyperylenol (3) displayed potent antifungal activity against Pestallozzia theae and Alternaria brassicicola with MIC values equal to those of carbendazim. The cytotoxicity of 1 and 2 against human lung carcinoma (A-549), human cervical carcinoma (HeLa), and human hepatoma (HepG2) cell lines were also evaluated.

Chemical profiling of two congeneric sea mat corals along the Brazilian coast: adaptive and functional patterns

Multisource metabolomics of two congeneric sea mat corals along the Brazilian coast suggested the major influence of environment on chemical divergence.

Penicilazaphilones D and E: two new azaphilones from a sponge-derived strain of the fungus Penicillium sclerotiorum

Two new azaphilones, penicilazaphilones D (1) and E (2), along with four known analogs (3–6), were obtained from the sponge-derived fungus Penicillium sclerotiorum.

Preparation, Structure, and Potent Antifouling Activity of Sclerotioramine Derivatives

A series of 30 sclerotioramine derivatives (2-31) of the natural compound, (+)-sclerotiorin (1), has been successfully semi-synthesized by a one-step reaction with high yields (up to 80%). The structures of these new derivatives were established by extensive spectroscopic methods and single-crystal X-ray diffraction analysis for 3, 6, and 10. (+)-Sclerotiorin (1) and its semisynthetic derivatives (2-31) were evaluated for their antifouling activity. Most of them except 6, 7, 8, 12, and 28 showed potent antifouling activity against the larval settlement of the barnacle Balanus amphitrite. More interestingly, most of the aromatic amino-derivatives (13-17, 19-21, 23, 25-27, and 29-31) showed strong antifouling activity; however, only two aliphatic amino-derivatives (5 and 10) had the activity.

The culturable mycobiota of Flabellia petiolata: First survey of marine fungi associated to a Mediterranean green alga

Algae-inhabiting marine fungi represent a taxonomically and ecologically interesting group of microorganisms still largely neglected, especially in temperate regions. The aim of this study was to isolate and to identify the culturable mycobiota associated with Flabellia petiolata, a green alga frequently retrieved in the Mediterranean basin. Twenty algal thalli were collected from two different sampling sites in the Mediterranean Sea (Elba Island, Italy). A polyphasic approach showed the presence of a relevant alga-associated mycobiota with 64 taxa identified. The fungal isolates belonged mainly to Ascomycota (61 taxa), while only three Basidiomycota were detected. The phylogenetic position of sterile mycelia and cryptic taxa, inferred on the basis of LSU partial region, highlighted the presence of putative new phylogenetic lineages within Dothideomycetes and Sordariomycetes. This work represents the first quali-quantitative analysis of the culturable mycobiota associated to a green alga in the Mediterranean Sea.

A new hexahydrobenzopyran derivative from the gorgonian-derived Fungus Eutypella sp

A new hexahydrobenzopyran derivative cytosporin L (1), and another eight known compounds were isolated from the gorgonian-derived fungus Eutypella sp. collected from the South China Sea. The structure of 1 was elucidated by comprehensive spectroscopic data. The absolute configuration of 1 was determined by a chemical reaction and the modified Mosher's method. The isolated secondary metabolites were evaluated for their antibacterial activities. Compound 1 showed antibacterial activity towards Micrococcus lysodeikticus and Enterobacter aerogenes with the same MIC values of 3.12 μM. Compounds 1-3 were evaluated for antiviral activities. Compounds 1 and 2 obviously inhibited the respiratory syncytial virus (RSV) with the IC₅₀ values of 72.01 and 30.25 μM, respectively.

The order Zoantharia Rafinesque, 1815 (Cnidaria, Anthozoa: Hexacorallia): supraspecific classification and nomenclature

Many supraspecific zoantharian names have long and complicated histories. The present list is provided to advise researchers on the current state of supraspecific nomenclature of the zoantharians, particularly given the recent attention paid to the taxonomy, phylogeny, and biodiversity of this order. At the same time, several taxonomic issues brought to light by recent research are resolved. Details on the taxonomic and nomenclatural history of most groups are provided, along with appendices of invalid supraspecific names.

Deep Subseafloor Fungi as an Untapped Reservoir of Amphipathic Antimicrobial Compounds

The evolving global threat of antimicrobial resistance requires a deep renewal of the antibiotic arsenal including the isolation and characterization of new drugs. Underexplored marine ecosystems may represent an untapped reservoir of novel bioactive molecules. Deep-sea fungi isolated from a record-depth sediment core of almost 2000 m below the seafloor were investigated for antimicrobial activities. This antimicrobial screening, using 16 microbial targets, revealed 33% of filamentous fungi synthesizing bioactive compounds with activities against pathogenic bacteria and fungi. Interestingly, occurrence of antimicrobial producing isolates was well correlated with the complexity of the habitat (in term of microbial richness), as higher antimicrobial activities were obtained at specific layers of the sediment core. It clearly highlights complex deep-sea habitats as chemical battlefields where synthesis of numerous bioactive compounds appears critical for microbial competition. The six most promising deep subseafloor fungal isolates were selected for the production and extraction of bioactive compounds. Depending on the fungal isolates, antimicrobial compounds were only biosynthesized in semi-liquid or solid-state conditions as no antimicrobial activities were ever detected using liquid fermentation. An exception was made for one fungal isolate, and the extraction procedure designed to extract amphipathic compounds was successful and highlighted the amphiphilic profile of the bioactive metabolites.

Nigrodiquinone A, a Hydroanthraquinone Dimer Containing a Rare C-9-C-7' Linkage from a Zoanthid-Derived Nigrospora sp. Fungus

One new hydroanthraquinone dimer with a rare C-9–C-7′ linkage, nigrodiquinone A (1), and four known anthraquinone monomers 2–5, were isolated from a fungus Nigrospora sp. obtained from the zoanthid Palythoa haddoni collected in the South China Sea. The structure of 1 was established through extensive NMR spectroscopy, and the absolute configuration was elucidated by comparing computed electronic circular dichroism (ECD) and optical rotations (OR) with experimental results. All the compounds were evaluated for antiviral activity, and 1 was also evaluated for antibacterial activity. Compound 4 displayed mild antiviral activity against coxsackie virus (Cox-B3) with the IC₅₀ value of 93.7 μM, and 5 showed an IC₅₀ value of 74.0 μM against respiratory syncytial virus (RSV).

Antimicrobials from Cnidarians. A New Perspective for Anti-Infective Therapy?

The ability of microbes to counter the scientific and therapeutic advancements achieved during the second half of the twentieth century to provide effective disease treatments is currently a significant challenge for researchers in biology and medicine. The discovery of antibiotics, and the subsequent development of synthetic antimicrobial compounds, altered our therapeutic approach towards infectious diseases, and improved the quality and length of life for humans and other organisms. The current alarming rise in cases of antibiotic-resistance has forced biomedical researchers to explore new ways to recognize and/or produce new antimicrobials or to find other approaches for existing therapeutics. Aquatic organisms are known to be a source of compounds having the potential to play a role in fighting the battle against pathogenic microbes. In this connection, cnidarians occupy a pre-eminent role. Over the past few decades several studies have explored the antimicrobial/antibiotic properties of cnidarian extracts with the aim of isolating compounds possessing useful therapeutic features. This paper aims to review the existing data on this subject, taking into account the possible utilization of identified compounds.

Antibacterial and antifungal compounds from marine fungi

This paper reviews 116 new compounds with antifungal or antibacterial activities as well as 169 other known antimicrobial compounds, with a specific focus on January 2010 through March 2015. Furthermore, the phylogeny of the fungi producing these antibacterial or antifungal compounds was analyzed. The new methods used to isolate marine fungi that possess antibacterial or antifungal activities as well as the relationship between structure and activity are shown in this review.