Three new sterigmatocystin analogues from marine-derived fungus Aspergillus versicolor MF359

Inhibitor of Chromosome Segregation in Pseudomonas aeruginosa from Fungal Extracts

Chromosome segregation is an essential cellular process that has the potential to yield numerous targets for drug development. This pathway is presently underutilized partially due to the difficulties in the development of robust reporter assays suitable for high throughput screening. In bacteria, chromosome segregation is mediated by two partially redundant systems, condensins and ParABS. Based on the synthetic lethality of the two systems, we developed an assay suitable for screening and then screened a library of fungal extracts for potential inhibitors of the ParABS pathway, as judged by their enhanced activity on condensin-deficient cells. We found such activity in extracts of Humicola sp. Fractionation of the extract led to the discovery of four new analogues of sterigmatocystin, one of which, 4-hydroxy-sterigmatocystin (4HS), displayed antibacterial activity. 4HS induced the phenotype typical for parAB mutants including defects in chromosome segregation and cell division. Specifically, bacteria exposed to 4HS produced anucleate cells and were impaired in the assembly of the FtsZ ring. Moreover, 4HS binds to purified ParB in a ParS-modulated manner and inhibits its ParS-dependent CTPase activity. The data describe a small molecule inhibitor of ParB and expand the known spectrum of activities of sterigmatocystin to include bacterial chromosome segregation.

Comparative metabolomics study on the secondary metabolites of the red alga, Corallina officinalis and its associated endosymbiotic fungi

Marine endosymbionts have gained remarkable interest in the last three decades in terms of natural products (NPs) isolated thereof, emphasizing the chemical correlations with those isolated from the host marine organism. The current study aimed to conduct comparative metabolic profiling of the marine red algae Corallina officinalis, and three fungal endosymbionts isolated from its inner tissues namely, Aspergillus nidulans, A. flavipes and A. flavus. The ethyl acetate (EtOAc) extracts of the host organism as well as the isolated endosymbionts were analyzed using ultra-high performance liquid chromatography coupled to high resolution tandem mass spectrometry (UHPLC-MS/MS)in both positive and negative ion modes, applying both full scan (FS) and all ion fragmentation (AIF) modes. Extensive interpretation of the LC-MS/MS spectra had led to the identification of 76 metabolites belonging to different phytochemical classes including alkaloids, polyketides, sesquiterpenes, butyrolactones, peptides, fatty acids, isocoumarins, quinones, among others. Metabolites were tentatively identified by comparing the accurate mass and fragmentation pattern with metabolites previously reported in the literature, as well as bioinformatics analysis using GNPS. A relationship between the host C. officinalis and its endophytes (A. flavus, A. nidulans, and A. flavipes) was discovered. C. officinalis shares common metabolites with at least one of the three endosymbiotic fungi. Some metabolites have been identified in endophytes and do not exist in their host. Multivariate analysis (MVA) revealed discrimination of A. flavipes from Corallina officinalis and other associated endophytic Aspergillus fungi (A. flavus and A. nidulans).

The Biosynthesis, Structure Diversity and Bioactivity of Sterigmatocystins and Aflatoxins: A Review

Sterigmatocystins and aflatoxins are a group of mycotoxins mainly isolated from fungi of the genera Aspergillus. Since the discovery of sterigmatocystins in 1954 and aflatoxins in 1961, many scholars have conducted a series of studies on their structural identification, synthesis and biological activities. Studies have shown that sterigmatocystins and aflatoxins have a wide range of biological activities such as antitumour, antibacterial, anti-inflammatory, antiplasmodial, etc. The sterigmatocystins and aflatoxins had been shown to be hepatotoxic and nephrotoxic in animals. This review attempts to give a comprehensive summary of progress on the chemical structural features, synthesis, and bioactivity of sterigmatocystins and aflatoxins reported from 1954 to April 2024. A total of 72 sterigmatocystins and 20 aflatoxins are presented in this review. This paper reviews the chemical diversity and potential activity and toxicity of sterigmatocystins and aflatoxins, enhances the understanding of sterigmatocystins and aflatoxins that adversely affect humans and animals, and provides ideas for their prevention, research and development.

Advances in Natural Products from the Marine-Sponge-Associated Microorganisms with Antimicrobial Activity in the Last Decade

Microorganisms are the dominating source of food and nutrition for sponges and play an important role in sponge structure, chemical defense, excretion and evolution. In recent years, plentiful secondary metabolites with novel structures and specific activities have been identified from sponge-associated microorganisms. Additionally, as the phenomenon of the drug resistance of pathogenic bacteria is becoming more and more common, it is urgent to discover new antimicrobial agents. In this paper, we reviewed 270 secondary metabolites with potential antimicrobial activity against a variety of pathogenic strains reported in the literature from 2012 to 2022. Among them, 68.5% were derived from fungi, 23.3% originated from actinomycetes, 3.7% were obtained from other bacteria and 4.4% were discovered using the co-culture method. The structures of these compounds include terpenoids (13%), polyketides (51.9%), alkaloids (17.4%), peptides (11.5%), glucosides (3.3%), etc. Significantly, there are 124 new compounds and 146 known compounds, 55 of which have antifungal activity in addition to antipathogenic bacteria. This review will provide a theoretical basis for the further development of antimicrobial drugs.

Urease and Carbonic Anhydrase Inhibitory Effect of Xanthones from Aspergillus nidulans, an Endophytic Fungus of Nyctanthes arbor-tristis

Urease plays a major role in the pathogenesis of peptic and gastric ulcer and also causes acute pyelonephritis and development of infection-induced reactive arthritis. Carbonic anhydrases (CA) cause pathological disorders such as epilepsy (CA I), glaucoma, gastritis, renal, pancreatic carcinomas, and malignant brain tumors (CA II). Although various synthetic urease and carbonic anhydrase inhibitors are known, these have many side effects. Hence, present studies were undertaken on ethyl acetate extract of Aspergillus nidulans, an endophytic fungus separated from the leaves of Nyctanthes arbor-tristis Linn. and led to the isolation of five furanoxanthones, sterigmatin (1: ), sterigmatocystin (3: ), dihydrosterigmatocystin (4: ), oxisterigmatocystin C (5: ), acyl-hemiacetal sterigmatocystin (6: ), and a pyranoxanthone (2: ). Acetylation of 3: gave compound O-acetyl sterigmatocystin (7: ). Their chemical structures were elucidated by ¹H and ¹³C NMR and MS. The inhibitory effect of isolated compounds was evaluated on urease and carbonic anhydrase (bCA II) enzymes in vitro. Compounds 3: and 6: showed significant urease inhibition (IC₅₀ 19 and 21 µM), while other compounds exhibited varying degrees of urease inhibition (IC₅₀ 33 - 51 µM). Compounds 4, 6: and 7: exhibited significant inhibition of bCA II (IC₅₀ values 21, 25 and 18 µM respectively), compounds 1: -3: displayed moderate inhibition (IC₅₀ 61, 76 and 31 µM respectively) while 5: showed no inhibition. A mechanistic study of the most active urease inhibitors was also performed using enzyme kinetics and molecular docking. All compounds were found non-toxic on the NIH-3T3 cell line.

Isolation of Bioactive Metabolites from Soil Derived Fungus-Aspergillus fumigatus

Fungi produce numerous secondary metabolites with intriguing biological properties for the health, industrial, and agricultural sectors. Herein, we report the high-yield isolation of phenolic natural products, N-formyl-4-hydroxyphenyl-acetamide 1 (~117 mg/L) and atraric acid 2 (~18 mg/L), from the ethyl acetate extract of the soil-derived fungus, Aspergillus fumigatus. The structures of compounds 1 and 2 were elucidated through the detailed spectroscopic analysis of NMR and LCMS data. These compounds were assayed for their antimicrobial activities. It was observed that compounds 1 and 2 exhibited strong inhibition against a series of fungal strains but only weak antibacterial properties against multi-drug-resistant strains. More significantly, this is the first known instance of the isolation of atraric acid 2 from a non-lichen fungal strain. We suggest the optimization of this fungal strain may exhibit elevated production of compounds 1 and 2, potentially rendering it a valuable source for the industrial-scale production of these natural antimicrobial compounds. Further investigation is necessary to establish the veracity of this hypothesis.

Anthraquinones and Their Analogues from Marine-Derived Fungi: Chemistry and Biological Activities

Anthraquinones are an interesting chemical class of polyketides since they not only exhibit a myriad of biological activities but also contribute to managing ecological roles. In this review article, we provide a current knowledge on the anthraquinoids reported from marine-derived fungi, isolated from various resources in both shallow waters such as mangrove plants and sediments of the mangrove habitat, coral reef, algae, sponges, and deep sea. This review also tentatively categorizes anthraquinone metabolites from the simplest to the most complicated scaffolds such as conjugated xanthone–anthraquinone derivatives and bianthraquinones, which have been isolated from marine-derived fungi, especially from the genera Apergillus, Penicillium, Eurotium, Altenaria, Fusarium, Stemphylium, Trichoderma, Acremonium, and other fungal strains. The present review, covering a range from 2000 to 2021, was elaborated through a comprehensive literature search using the following databases: ACS publications, Elsevier, Taylor and Francis, Wiley Online Library, MDPI, Springer, and Thieme. Thereupon, we have summarized and categorized 296 anthraquinones and their derivatives, some of which showed a variety of biological properties such as enzyme inhibition, antibacterial, antifungal, antiviral, antitubercular (against Mycobacterium tuberculosis), cytotoxic, anti-inflammatory, antifouling, and antioxidant activities. In addition, proposed biogenetic pathways of some anthraquinone derivatives are also discussed.

Identification of Potential Anti-Neuroinflammatory Inhibitors from Antarctic Fungal Strain Aspergillus sp. SF-7402 via Regulating the NF-κB Signaling Pathway in Microglia

Microglia play a significant role in immune defense and tissue repair in the central nervous system (CNS). Microglial activation and the resulting neuroinflammation play a key role in the pathogenesis of neurodegenerative disorders. Recently, inflammation reduction strategies in neurodegenerative diseases have attracted increasing attention. Herein, we discovered and evaluated the anti-neuroinflammatory potential of compounds from the Antarctic fungi strain Aspergillus sp. SF-7402 in lipopolysaccharide (LPS)-stimulated BV2 cells. Four metabolites were isolated from the fungi through chemical investigations, namely, 5-methoxysterigmatocystin (1), sterigmatocystin (2), aversin (3), and 6,8-O-dimethylversicolorin A (4). Their chemical structures were elucidated by extensive spectroscopic analysis and HR-ESI-MS, as well as by comparison with those reported in literature. Anti-neuroinflammatory effects of the isolated metabolites were evaluated by measuring the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in LPS-activated microglia at non-cytotoxic concentrations. Sterigmatocystins (1 and 2) displayed significant effects on NO production and mild effects on TNF-α and IL-6 expression inhibition. The molecular mechanisms underlying this activity were investigated using Western blot analysis. Sterigmatocystin treatment inhibited NO production via downregulation of inducible nitric oxide synthase (iNOS) expression in LPS-stimulated BV2 cells. Additionally, sterigmatocystins reduced nuclear translocation of NF-κB. These results suggest that sterigmatocystins present in the fungal strain Aspergillus sp. are promising candidates for the treatment of neuroinflammatory diseases.

Bioactive Marine Xanthones: A Review

The marine environment is an important source of specialized metabolites with valuable biological activities. Xanthones are a relevant chemical class of specialized metabolites found in this environment due to their structural variety and their biological activities. In this work, a comprehensive literature review of marine xanthones reported up to now was performed. A large number of bioactive xanthone derivatives (169) were identified, and their structures, biological activities, and natural sources were described. To characterize the chemical space occupied by marine-derived xanthones, molecular descriptors were calculated. For the analysis of the molecular descriptors, the xanthone derivatives were grouped into five structural categories (simple, prenylated, O-heterocyclic, complex, and hydroxanthones) and six biological activities (antitumor, antibacterial, antidiabetic, antifungal, antiviral, and miscellaneous). Moreover, the natural product-likeness and the drug-likeness of marine xanthones were also assessed. Marine xanthone derivatives are rewarding bioactive compounds and constitute a promising starting point for the design of other novel bioactive molecules.

Antitubercular metabolites from the marine-derived fungus strain Aspergillus fumigatus MF029

During the systematic screening of bioactive compounds from our marine natural product library, crude extract of the marine-derived fungus strain Aspergillus fumigatus MF029 exhibited moderate bioactivities against Bacillus subtilis, Staphylococcus aureus, methicillin-resistant S. aureus, and Mycobacterium bovis bacillus Calmette-Guérin (BCG). Further chemical investigation resulted in the identification of two new compounds, chaetominine A (1) and sphingofungin I (2), together with four known compounds, emodin (3), chaetominine (4), sphingofungin D (5) and trypacidin (6). Trypacidin displayed potential antitubercular activity with MIC value of 1.25 μg/mL.

Marine Sponge-Associated Fungi as Potential Novel Bioactive Natural Product Sources for Drug Discovery: A Review

Marine sponge-associated fungi are promising sources of structurally interesting and bioactive secondary metabolites. Great plenty of natural products have been discovered from spongeassociated fungi in recent years. Here reviewed are 571 new compounds isolated from marine fungi associated with sponges in 2010-2018. These molecules comprised eight different structural classes, including alkaloids, polyketides, terpenoids, meroterpenoids, etc. Moreover, most of these compounds demonstrated profoundly biological activities, such as antimicrobial, antiviral, cytotoxic, etc. This review systematically summarized the structural diversity, biological function, and future potential of these novel bioactive natural products for drug discovery.

Antibacterial Secondary Metabolites from Marine-Derived Fungus Aspergillus sp. IMCASMF180035

Four new secondary metabolites, including one spiro[anthracenone-xanthene] derivative aspergiloxathene A (1), one penicillide analogue, Δ^2′-1′-dehydropenicillide (2), and two new phthalide derivatives, 5-methyl-3-methoxyepicoccone (3) and 7-carboxy-4-hydroxy-6-methoxy-5-methylphthalide (4), together with four known compounds, yicathin C (5), dehydropenicillide (6), 3-methoxyepicoccone (7), 4-hydroxy-6-methoxy-5-methylphthalide (8), were identified from the marine-derived fungus Aspergillus sp. IMCASMF180035. Their structures were determined by spectroscopic data, including high-resolution electrospray ionization mass spectrometry (HRESIMS), 1D and 2D nuclear magnetic resonance (NMR) techniques. Compound 1 was identified as the first jointed molecule by xanthene and anthracenone moieties possessing an unprecedented carbon skeleton with spiro-ring system. All compounds were evaluated activities against Staphylococcus aureus, methicillin resistant S. aureus (MRSA), Escherichia coli, Escherichia faecium, Pseudomonas aeruginosa, and Helicobacter pylori. Compound 1 showed significant inhibitory effects against S. aureus and MRSA, with minimum inhibitory concentration (MIC) values of 5.60 and 22.40 µM. Compounds 2 and 6 exhibited potent antibacterial activities against H. pylori, with MIC values of 21.73 and 21.61 µM, respectively.

Bioassay-guided isolation and characterization of antibacterial compound from Aspergillus fumigatus HX-1 associated with Clam

This study aimed to identify a symbiotic fungus strain HX-1 with anti-Vibrio harveyi activity and isolate and identify the active compound. The HX-1 strain was identified as Aspergillus fumigatus according to the morphological characteristics and internal transcribed spacer (ITS) sequence analysis. The compound was isolated from the fermentation product of HX-1 strain through ethyl acetate extraction, silica gel and Sephadex LH-20 column chromatography, and semi-preparative HPLC techniques using an antibacterial-guided fractionation method. According to its physicochemical properties and spectral characteristics, the compound was identified as trypacidin having the same anti-V. harveyi activity as streptomycin sulfate, with the minimum inhibitory concentration of 31.25 µg/mL.

Marine Fungus Aspergillus chevalieri TM2-S6 Extract Protects Skin Fibroblasts from Oxidative Stress

The strain Aspergillus chevalieri TM2-S6 was isolated from the sponge Axinella and identified according to internal transcribed spacer (ITS) molecular sequence homology with Aspergillus species from the section Restricti. The strain was cultivated 9 days on potato dextrose broth (PDB), and the medium evaluated as antioxidant on primary normal human dermal fibroblasts (NHDF). The cultivation broth was submitted to sterile filtration, lyophilized and used without any further processing to give the Aspergillus chevalieri TM2-S6 cultivation broth ingredient named ACBB. ACCB contains two main compounds: tetrahydroauroglaucin and flavoglaucin. Under oxidative stress, ACCB showed a significant promotion of cell viability. To elucidate the mechanism of action, the impact on a panel of hundreds of genes involved in fibroblast physiology was evaluated. Thus, ACCB stimulates cell proliferation (VEGFA, TGFB3), antioxidant response (GPX1, SOD1, NRF2), and extracellular matrix organization (COL1A1, COL3A1, CD44, MMP14). ACCD also reduced aging (SIRT1, SIRT2, FOXO3). These findings indicate that Aspergillus chevalieri TM2-S6 cultivation broth exhibits significant in vitro skin protection of human fibroblasts under oxidative stress, making it a potential cosmetic ingredient.

In vitro protective effects of marine-derived Aspergillus puulaauensis TM124-S4 extract on H2O2-stressed primary human fibroblasts

Nowadays, there is a huge interest in natural products obtained from marine organisms that can promote human health.The aim of the present study is to evaluate for the first time, the in vitro effects of marine Aspergillus puulaauensis TM124-S4 extract against oxidative stress in human fibroblasts, and its potential as a cosmetic ingredient. The strain was isolated from the Mediterranean Sea star, Echinaster sepositus, and identified according to ITS molecular sequence homology as a member of Aspergillus section versicolores.To gain insight on the bioactivity underpinning the effects of TM124-S4 extract on oxidative stress, we examined a panel of a hundred genes as well as cell viability. Initially, Aspergillus puulaauensis TM124-S4 promoted cell viability.The change in gene transcripts revealed that Aspergillus puulaauensis TM124-S4 extracts exhibited skin protection properties by mediating cell proliferation (EPS8, GDF15, CASP7, VEGFA), antioxidant response (CAT, SOD1, TXN, GPX1), skin hydration (CD44, CRABP2, SERPINE) and DNA repair (PCNA, P21). The extract also modulated the expression of genes involved in skin pigmentation and aging (TYR, FOXO3).These findings indicate that Aspergillus puulaauensis TM124-S4 extract possesses significant in-vitro skin protection activity against induced oxidative stress.Furthermore, new insights are provided into the beneficial role of fungal bioactive compounds in skin related research.

Biological and Chemical Diversity of Marine Sponge-Derived Microorganisms over the Last Two Decades from 1998 to 2017

Marine sponges are well known as rich sources of biologically natural products. Growing evidence indicates that sponges harbor a wealth of microorganisms in their bodies, which are likely to be the true producers of bioactive secondary metabolites. In order to promote the study of natural product chemistry and explore the relationship between microorganisms and their sponge hosts, in this review, we give a comprehensive overview of the structures, sources, and activities of the 774 new marine natural products from sponge-derived microorganisms described over the last two decades from 1998 to 2017.

Enhanced production of questin by marine-derived Aspergillus flavipes HN4-13

Questin has favorable applications. Fractional factorial design, Box-Behnken design, and response surface methodology were adopted to optimize the fermentation conditions of the marine-derived fungus, Aspergillus flavipes HN4-13, thereby enhancing questin production. Optimal fermentation conditions in a 500-mL conical flask with 200 mL of medium were 4% soluble starch, 0.9% beef extract, 4% NaCl, 0.05% Na₂HPO₄, pH 6, 2% inoculum size, and shaking at 28 ℃ and 160 rpm/min for 7 days. The production of questin can achieve 64.93 ± 4.55 mg/L, with no significant difference from the predicted value (66.27 mg/L). Thus, this optimized process of questin production is feasible. Such production is 17-fold higher than that of the basal Sabouraud's dextrose medium. Results indicate the potential of A. flavipes HN4-13 in the large-scale production of questin through fermentation.

Secondary Metabolites from Marine-Derived Fungi from China

Marine-derived fungi play an important role in the search for structurally unique secondary metabolites, some of which show promising pharmacological activities that make them useful leads for drug discovery. Marine natural product research in China in general has made enormous progress in the last two decades as described in this chapter on fungal metabolites. This contribution covers 613 new natural products reported from 2001 to 2017 from marine-derived fungi obtained from algae, sponges, corals, and other marine organisms from Chinese waters. The genera Aspergillus (170 new natural products, 28%) and Penicillium (70 new natural products, 11%) were the main fungal producers of new natural products during the time period covered, whereas sponges (184 new natural products, 30%) were the most abundant source of new natural products, followed by corals (154 new natural products, 25%) and algae (130 new natural products, 21%). Close to 40% of all natural products covered in this contribution displayed various bioactivities. The major bioactivities reported were cytotoxicity against different cancer cell lines, antimicrobial (mainly antibacterial) activity, and antiviral activity, which accounted for 13%, 9%, and 3% of all natural products reported. In terms of structural classes, polyketides (188 new natural products, 31%) play a dominant role, and if prenylated polyketides and nitrogen-containing polyketides (included in meroterpenes and alkaloids in this contribution) are taken into account, their total number even exceeds 50%. Nitrogen-containing compounds including peptides (65 new natural products, 10%) and alkaloids (103 new natural products, 17%) are the second largest group.

Unique Aggregation of Sterigmatocystin in Water Yields Strong and Specific Circular Dichroism Response Allowing Highly Sensitive and Selective Monitoring of Bio-Relevant Interactions

We demonstrated the hitherto unknown property of the mycotoxin sterigmatocystin (STC) to provide homogeneous solutions in aqueous medium by forming a unique aggregate type (not formed by analogous aflatoxins), characterized by exceptionally strong circular dichroism (CD) bands in the 300-400 nm range. Results showed that these CD bands do not originate from intrinsic STC chirality but are a specific property of a peculiar aggregation process similar to psi-DNA CD response. Transmission electron microscopy (TEM) experiments revealed a fine fiber network resembling a supramolecular gel structure with helical fibers. Thermodynamic studies of aggregates by differential scanning calorimetry (DSC) revealed high reversibility of the dominant aggregation process. We demonstrated that the novel STC psi-CD band at 345 nm could be applied at biorelevant conditions (100 nanomolar concentration) and even in marine-salt content conditions for specific and quantitative monitoring of STC. Also, we showed that STC strongly non-covalently interacts with ds-DNA with likely toxic effects, thus contrary to the previous belief requiring prior enzyme epoxidation.

New Diketopiperazines from a Marine-Derived Fungus Strain Aspergillus versicolor MF180151

Six new diketopiperazines, (±)-7,8-epoxy-brevianamide Q ((±)-1), (±)-8-hydroxy-brevianamide R ((±)-2), and (±)-8-epihydroxy-brevianamide R ((±)-3), together with four known compounds, (±)-brevianamide R ((±)-4), versicolorin B (5) and averufin (6), were isolated from a marine-derived fungus strain Aspergillus versicolor MF180151, which was recovered from a sediment sample collected from the Bohai Sea, China. The chemical structures were established by 1D- and 2D-NMR spectra and HR-ESI-MS. 1 is the first sample of brevianamides with an epoxy moiety. Their bioactivities were evaluated against Candida albicans, Bacillus subtilis, Staphylococcus aureus, methicillin-resistant S. aureus, Pseudomonas aeruginosa, and Bacillus Calmette-Guérin. Compounds 1–4 showed no activities against the pathogens, and compounds 5 and 6 showed moderate activities against S. aureus and methicillin-resistant S. aureus.

Structures, Activities and Drug-Likeness of Anti-Infective Xanthone Derivatives Isolated from the Marine Environment: A Review

Marine organisms represent almost half of total biodiversity and are a very important source of new bioactive substances. Within the varied biological activities found in marine products, their antimicrobial activity is one of the most relevant. Infectious diseases are responsible for high levels of morbidity and mortality and many antimicrobials lose their effectiveness with time due to the development of resistance. These facts justify the high importance of finding new, effective and safe anti-infective agents. Among the variety of biological activities of marine xanthone derivatives, one that must be highlighted is their anti-infective properties. In this work, a literature review of marine xanthones with anti-infective activity, namely antibacterial, antifungal, antiparasitic and antiviral, is presented. Their structures, biological activity, sources and the methods used for bioactivity evaluation are described. The xanthone derivatives are grouped in three sets: xanthones, hydroxanthones and glycosylated derivatives. Moreover, molecular descriptors, biophysico-chemical properties, and pharmacokinetic parameters were calculated, and the chemical space occupied by marine xanthone derivatives is recognized. The chemical space was compared with marketed drugs and framed accordingly to the drug-likeness concept in order to profile the pharmacokinetic of anti-infective marine xanthone derivatives.

Antibacterial activity and action mechanism of questin from marine Aspergillus flavipes HN4-13 against aquatic pathogen Vibrio harveyi

This study investigated the antibacterial activity and mechanism of questin from marine Aspergillus flavipes HN4-13 against aquatic pathogenic Vibrio harveyi. The minimal inhibitory concentration and minimal bactericidal concentration of questin against V. harveyi strain SZ-1 and 1.8690 were determined by Oxford cup and tube dilution methods. The mechanism of action of questin against V. harveyi 1.8690 was investigated by bacterial growth curve analysis, ultraviolet absorption, Mo-Sb-Vc colorimetry, alkaline phosphatase and scanning electron microscopy. Results showed that questin exhibited favourable antibacterial and bactericidal activity against V. harveyi by disrupting the cell wall and membrane, which caused the destruction of permeability and integrity of cell wall and membrane, resulting in the leakage of intracellular biological components and change of cell morphology. This paper is the first to report the mechanism of action of questin against the aquatic pathogen V. harveyi.

Optimized production and isolation of antibacterial agent from marine Aspergillus flavipes against Vibrio harveyi

Statistical methodologies, including Plackett-Burman design and Box-Behnken design, were employed to optimize the fermentation conditions for the production of active substances against aquatic pathogen Vibrio harveyi by marine-derived Aspergillus flavipes strain HN4-13. The optimal crucial fermentation values for maximum production of active substances against V. harveyi were obtained as follows: X₁ (peptone) = 0.3%, X₂ (KCl) = 0.25%, and X₃ (inoculum size) = 4.5%. The predicted diameter of inhibitory zone against V. harveyi was 23.39 mm, and the practical value reached 23.71 ± 0.98 mm with a 62.3% increase. Bioassay-guided fractionation resulted in the acquisition of two compounds whose structures were identified as questin (1) and emodin (2). Questin exhibited the same antibacterial activity against V. harveyi as streptomycin (MIC 31.25 µg/mL). This is the first time to report questin as a potential antibacterial agent against aquatic pathogen V. harveyi.

In-vitro evaluation of marine derived fungi against Cutibacterium acnes

Cutibacterium acnes (or Propionibacterium acnes) is the main target for the prevention and medical treatment of acne vulgaris. The aim of this study was to evaluate the in vitro anti-C. acnes and anti-S. epidermidis properties of some marine fungi isolated from different Indian marine environments. Seventy fungal isolates were obtained from samples collected from the west coasts and Andaman Island, India. Methanol extracts of 35 isolates were screened for their antibacterial properties and 5 out of the 35 isolates displayed significant inhibition as compared with tetracycline. DNA was successfully extracted from these five fungal isolates and phylogenetic analysis was performed. The methanol extracts possessed antibacterial activity against C. acnes and S. epidermidis with MIC values ranged from 0.8 mg/mL to 1 mg/mL. SEM analysis revealed that the extract induces deleterious morphological changes in the bacterial cell membrane. This study has identified some fungi extracts with significant antibacterial activity. The extracts may have potential for development as an antibacterial agent in the treatment of acne vulgaris.

Current Status and Future Prospects of Marine Natural Products (MNPs) as Antimicrobials

The marine environment is a rich source of chemically diverse, biologically active natural products, and serves as an invaluable resource in the ongoing search for novel antimicrobial compounds. Recent advances in extraction and isolation techniques, and in state-of-the-art technologies involved in organic synthesis and chemical structure elucidation, have accelerated the numbers of antimicrobial molecules originating from the ocean moving into clinical trials. The chemical diversity associated with these marine-derived molecules is immense, varying from simple linear peptides and fatty acids to complex alkaloids, terpenes and polyketides, etc. Such an array of structurally distinct molecules performs functionally diverse biological activities against many pathogenic bacteria and fungi, making marine-derived natural products valuable commodities, particularly in the current age of antimicrobial resistance. In this review, we have highlighted several marine-derived natural products (and their synthetic derivatives), which have gained recognition as effective antimicrobial agents over the past five years (2012–2017). These natural products have been categorized based on their chemical structures and the structure-activity mediated relationships of some of these bioactive molecules have been discussed. Finally, we have provided an insight into how genome mining efforts are likely to expedite the discovery of novel antimicrobial compounds.

Madurastatin B3, a rare aziridine derivative from actinomycete Nocardiopsis sp. LS150010 with potent anti-tuberculosis activity

Since the discovery of the first antibiotic, natural products have played an important role in chemistry, biology and medicine. To explore the potential of bioactive compounds from microbes isolated from the southeast of Tibet, China, a crude extract library was constructed and screened against Staphylococcus aureus. The strain Nocardiopsis sp. LS150010 was scaled up and subjected to further chemical studies, resulting in the identification of N-salicyloyl-2-aminopropan-1,3-diol (2) and its rare aziridine derivative, madurastatin B3 (1). Their structures were determined by detailed analysis of 1D, 2D NMR and HRMS data. Compounds 1 and 2 displayed significant inhibitory activity against S. aureus and methicillin resistant S. aureus, with MIC values of 6.25 µg/mL. Compound 1 also showed potent inhibitory activity against Bacillus subtilis and Escherichia coli, as well as activity in a Mycobacterium tuberculosis Bacillus Calmette-Guérin infected THP-1 cell model.

Bioprospecting Sponge-Associated Microbes for Antimicrobial Compounds

Sponges are the most prolific marine organisms with respect to their arsenal of bioactive compounds including antimicrobials. However, the majority of these substances are probably not produced by the sponge itself, but rather by bacteria or fungi that are associated with their host. This review for the first time provides a comprehensive overview of antimicrobial compounds that are known to be produced by sponge-associated microbes. We discuss the current state-of-the-art by grouping the bioactive compounds produced by sponge-associated microorganisms in four categories: antiviral, antibacterial, antifungal and antiprotozoal compounds. Based on in vitro activity tests, identified targets of potent antimicrobial substances derived from sponge-associated microbes include: human immunodeficiency virus 1 (HIV-1) (2-undecyl-4-quinolone, sorbicillactone A and chartarutine B); influenza A (H1N1) virus (truncateol M); nosocomial Gram positive bacteria (thiopeptide YM-266183, YM-266184, mayamycin and kocurin); Escherichia coli (sydonic acid), Chlamydia trachomatis (naphthacene glycoside SF2446A2); Plasmodium spp. (manzamine A and quinolone 1); Leishmania donovani (manzamine A and valinomycin); Trypanosoma brucei (valinomycin and staurosporine); Candida albicans and dermatophytic fungi (saadamycin, 5,7-dimethoxy-4-p-methoxylphenylcoumarin and YM-202204). Thirty-five bacterial and 12 fungal genera associated with sponges that produce antimicrobials were identified, with Streptomyces, Pseudovibrio, Bacillus, Aspergillus and Penicillium as the prominent producers of antimicrobial compounds. Furthemore culture-independent approaches to more comprehensively exploit the genetic richness of antimicrobial compound-producing pathways from sponge-associated bacteria are addressed.

Potential Pharmacological Resources: Natural Bioactive Compounds from Marine-Derived Fungi

In recent years, a considerable number of structurally unique metabolites with biological and pharmacological activities have been isolated from the marine-derived fungi, such as polyketides, alkaloids, peptides, lactones, terpenoids and steroids. Some of these compounds have anticancer, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, antibiotic and cytotoxic properties. This review partially summarizes the new bioactive compounds from marine-derived fungi with classification according to the sources of fungi and their biological activities. Those fungi found from 2014 to the present are discussed.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) 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 (1378 in 456 papers for 2014), 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.

Cannabis microbiome sequencing reveals several mycotoxic fungi native to dispensary grade Cannabis flowers

The Center for Disease Control estimates 128,000 people in the U.S. are hospitalized annually due to food borne illnesses. This has created a demand for food safety testing targeting the detection of pathogenic mold and bacteria on agricultural products. This risk extends to medical Cannabis and is of particular concern with inhaled, vaporized and even concentrated Cannabis products . As a result, third party microbial testing has become a regulatory requirement in the medical and recreational Cannabis markets, yet knowledge of the Cannabis microbiome is limited. Here we describe the first next generation sequencing survey of the fungal communities found in dispensary based Cannabis flowers by ITS2 sequencing, and demonstrate the sensitive detection of several toxigenic Penicillium and Aspergillus species, including P. citrinum and P. paxilli, that were not detected by one or more culture-based methods currently in use for safety testing.

Cannabis microbiome sequencing reveals several mycotoxic fungi native to dispensary grade Cannabis flowers

The Center for Disease Control estimates 128,000 people in the U.S. are hospitalized annually due to food borne illnesses. This has created a demand for food safety testing targeting the detection of pathogenic mold and bacteria on agricultural products. This risk extends to medical Cannabis and is of particular concern with inhaled, vaporized and even concentrated Cannabis products . As a result, third party microbial testing has become a regulatory requirement in the medical and recreational Cannabis markets, yet knowledge of the Cannabis microbiome is limited. Here we describe the first next generation sequencing survey of the microbial communities found in dispensary based Cannabis flowers and demonstrate the limitations in the culture-based regulations that are being superimposed from the food industry.

Development of the dichlorvos-ammonia (DV-AM) method for the visual detection of aflatoxigenic fungi

Aflatoxins (AFs) are carcinogenic and toxic secondary metabolites produced mainly by Aspergillus flavus and Aspergillus parasiticus. To monitor and regulate the AF contamination of crops, a sensitive and precise detection method for these toxigenic fungi in environments is necessary. We herein developed a novel visual detection method, the dichlorvos-ammonia (DV-AM) method, for identifying AF-producing fungi using DV and AM vapor on agar culture plates, in which DV inhibits the esterase in AF biosynthesis, causing the accumulation of anthraquinone precursors (versiconal hemiacetal acetate and versiconol acetate) of AFs in mycelia on the agar plate, followed by a change in the color of the colonies from light yellow to brilliant purple-red by the AM vapor treatment. We also investigated the appropriate culture conditions to increase the color intensity. It should be noted that other species producing the same precursors of AFs such as Aspergillus nidulans and Aspergillus versicolor could be discriminated from the Aspergillus section Flavi based on the differences of their phenotypes. The DV-AM method was also useful for the isolation of nonaflatoxigenic fungi showing no color change, for screening microorganisms that inhibit the AF production by fungi, and for the characterization of the fungi infecting corn kernels. Thus, the DV-AM method can provide a highly sensitive and visible indicator for the detection of aflatoxigenic fungi.

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.