Antibacterial anthraquinone derivatives isolated from a mangrove-derived endophytic fungus Aspergillus nidulans by ethanol stress strategy

One new polyketide and four new sesquiterpenes derivatives from the fungicolous fungi aspergillus nidulans LZ8 of Ganoderma lingzhi

One new polyketide asperfuranone D (1), four new sesquiterpenes derivatives aspergillone C-F (2-5) and three known compounds (6-8) were successfully isolated from Aspergillus nidulans LZ8, a fungicolous fungi from the macrofungal Ganoderma lingzhi. The structures of these compounds were elucidated by extensive spectroscopic analyses including ultraviolet-visible spectroscopy (UV), mass spectrometry (MS), nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD) calculation. In addition, the anti-inflammatory activities of the new compounds were evaluated using LPS-induced RAW 264.7 cells. The results revealed that compound 5 showed moderate nitric oxide (NO) inhibitory activity with the IC50 value of 13.19 ± 1.05 μM, while the IC50 value of the positive control L-NMMA was 41.88 ± 0.91 μM.

Significance of research on natural products from marine-derived Aspergillus species as a source against pathogenic bacteria

Bacterial infections pose a significant clinical burden on global health. The growing incidence of drug-resistant pathogens highlights the critical necessity to identify and isolate bioactive compounds from marine resources. Marine-derived fungi could provide novel lead compounds against pathogenic bacteria. Due to the particularity of the marine environment, Aspergillus species derived from marine sources have proven to be potent producers of bioactive secondary metabolites and have played a considerable role in advancing drug development. This study reviews the structural diversity and activities against pathogenic bacteria of secondary metabolites isolated from marine-derived Aspergillus species over the past 14 years (January 2010-June 2024), and 337 natural products (including 145 new compounds) were described. The structures were divided into five major categories-terpenoids, nitrogen-containing compounds, polyketides, steroids, and other classes. These antimicrobial metabolites will offer lead compounds to the development and innovation of antimicrobial agents.

Naturally Occurring Xanthones; Biological Activities, Chemical Profiles and In Silico Drug Discovery

Xanthones are widely distributed polyphenols, present commonly in higher plants; Garcinia, Calophyllum, Hypericum, Platonia, Mangifera, Gentiana and Swertia. Xanthone tricyclic scaffold is able to interact with different biological targets, showing antibacterial and cytotoxic effects, as well as potent effects against osteoarthritis, malaria, and cardiovascular diseases. Thus, in this article we focused on pharmacological effects, applications and preclinical studies with the recent updates of xanthon´s isolated compounds from 2017-2020. We found that only α-mangostin, gambogic acid, and mangiferin, have been subjected to preclinical studies with particular emphasis on the development of anticancer, diabetes, antimicrobial and hepatoprotective therapeutics. Molecular docking calculations were performed to predict the binding affinities of xanthone-derived compounds against SARS-CoV-2 M^pro. According to the results, cratoxanthone E and morellic acid demonstrated promising binding affinities towards SARS-CoV-2 M^pro with docking scores of -11.2 and -11.0 kcal/mol, respectively. Binding features manifested the capability of cratoxanthone E and morellic acid to exhibit nine and five hydrogen bonds, respectively, with the key amino acids of the M^pro active site. In conclusion, cratoxanthone E and morellic acid are promising anti-COVID-19 drug candidates that warrant further detailed in vivo experimental estimation and clinical assessment.

A new steroid with potent antimicrobial activities and two new polyketides from Penicillium variabile EN-394, a fungus obtained from the marine red alga Rhodomela confervoides

Three new compounds, including one steroid named penivariod A (1) and two polyketides penivarides A and B (2 and 3), as well as six known derivatives (4-9) were isolated from Penicillium variabile EN-394, a fungus afforded from the marine red alga Rhodomela confervoides. Their structures were elucidated by analysis of the HRESIMS, 1D and 2D NMR. The absolute stereochemistry was determined by X-ray crystallographic data, gauge-independent atomic orbital (GIAO) NMR shift calculation followed by DP4+ analysis combined with calculated electronic circular dichroism (ECD). Antimicrobial activities for the new compounds (1-3) were evaluated against human- and aquatic-pathogenic bacteria as well as plant pathogenic fungi. Compound 1 exhibited potent antimicrobial activity against most of the pathogenic strains, especially for Escherichia coli and Pseudomonas aeruginosa, with MIC values of 1.0 and 2.0 μg ml-1, respectively.

Mangrove-associated endomycota: diversity and functional significance as a source of novel drug leads

Endophytic fungi are known for their unprecedented ability to produce novel lead compounds of clinical and pharmaceutical importance. This review focuses on the unexplored fungal diversity associated with mangroves, emphasizing their biodiversity, distribution, and methodological approaches targeting isolation, and identification. Also highlights the bioactive compounds reported from the mangrove fungal endophytes. The compounds are categorized according to their reported biological activities including antimicrobial, antioxidant and cytotoxic property. In addition, protein kinase, α-glucosidase, acetylcholinesterase, tyrosinase inhibition, antiangiogenic, DNA-binding affinity, and calcium/potassium channel blocking activity are also reported. Exploration of these endophytes as a source of pharmacologically important compounds will be highly promising in the wake of emerging antibiotic resistance among pathogens. Thus, the aim of this review is to present a detailed report of mangrove derived endophytic fungi and to open an avenue for researchers to discover the possibilities of exploring these hidden mycota in developing novel drug leads.

Citriquinolinones A and B: Rare Isoquinolinone-Embedded Citrinin Analogues and Related Metabolites from the Deep-Sea-Derived Aspergillus versicolor 170217

A systematic chemical investigation of the deep-sea-derived fungus Aspergillus versicolor 170217 resulted in the isolation of six new (1-6) and 45 known (7-51) compounds. The structures of the new compounds were established on the basis of exhaustive analysis of their spectroscopic data and theoretical-statistical approaches including GIAO-NMR, TDDFT-ECD/ORD calculations, DP4+ probability analysis, and biogenetic consideration. Citriquinolinones A (1) and B (2) feature a unique isoquinolinone-embedded citrinin scaffold, representing the first exemplars of a citrinin-isoquinolinone hybrid. Dicitrinones K-L (3-4) are two new dimeric citrinin analogues with a rare CH-CH3 bridge. Biologically, frangula-emodin (32) and diorcinol (17) displayed remarkable anti-food allergic activity with IC50 values of 7.9 ± 3.0 μM and 13.4 ± 1.2 μM, respectively, while diorcinol (17) and penicitrinol A (20) exhibited weak inhibitory activity against Vibrio parahemolyticus, with MIC values ranging from 128 to 256 μM.

Aspergillus nidulans—Natural Metabolites Powerhouse: Structures, Biosynthesis, Bioactivities, and Biotechnological Potential

Nowadays, finding out new natural scaffolds of microbial origin increases at a higher rate than in the past decades and represents an auspicious route for reinvigorating the pool of compounds entering pharmaceutical industries. Fungi serve as a depository of fascinating, structurally unique metabolites with considerable therapeutic significance. Aspergillus genus represents one of the most prolific genera of filamentous fungi. Aspergillus nidulans Winter G. is a well-known and plentiful source of bioactive metabolites with abundant structural diversity, including terpenoids, benzophenones, sterols, alkaloids, xanthones, and polyketides, many of which display various bioactivities, such as cytotoxicity, antioxidant, anti-inflammatory, antiviral, and antimicrobial activities. The current work is targeted to survey the reported literature on A. nidulans, particularly its metabolites, biosynthesis, and bioactivities, in addition to recent reports on its biotechnological potential. From 1953 till November 2022, relying on the stated data, 206 metabolites were listed, with more than 100 references.

Chemical diversity, medicinal potentialities, biosynthesis, and pharmacokinetics of anthraquinones and their congeners derived from marine fungi: a comprehensive update

Marine fungi receive excessive attention as prolific producers of structurally unique secondary metabolites, offering promising potential as substitutes or conjugates for current therapeutics, whereas existing research has only scratched the surface in terms of secondary metabolite diversity and potential industrial applications as only a small share of bioactive natural products have been identified from marine-derived fungi thus far. Anthraquinones derived from filamentous fungi are a distinct large group of polyketides containing compounds which feature a common 9,10-dioxoanthracene core, while their derivatives are generated through enzymatic reactions such as methylation, oxidation, or dimerization to produce a large variety of anthraquinone derivatives. A considerable number of reported anthraquinones and their derivatives have shown significant biological activities as well as highly economical, commercial, and biomedical potentialities such as anticancer, antimicrobial, antioxidant, and anti-inflammatory activities. Accordingly, and in this context, this review comprehensively covers the state-of-art over 20 years of about 208 structurally diverse anthraquinones and their derivatives isolated from different species of marine-derived fungal genera along with their reported bioactivity wherever applicable. Also, in this manuscript, we will present in brief recent insights centred on their experimentally proved biosynthetic routes. Moreover, all reported compounds were extensively investigated for their in-silico drug-likeness and pharmacokinetics properties which intriguingly highlighted a list of 20 anthraquinone-containing compounds that could be considered as potential drug lead scaffolds.

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.

Biotechnological applications of mangrove plants and their isolated compounds in medicine-a mechanistic overview

Mangrove plants, also known as halophytes, are ecologically important plants that grow in various tropical and subtropical intertidal regions. Owing to the extreme abiotic and biotic stressful conditions they thrive in, these plants produce unique compounds with promising pharmacological propensities. Mangroves are inhabited by an astronomical number of fungal communities which produce a diverse array of extracellular degradative enzymes, namely: amylase, cellulase, xylanase, pectinase, cholesterol oxidase, etc. Such enzymes can be isolated from the mangrove fungi and harnessed for different biotechnological applications, for example, as replacements for chemical catalysts. Mangrove microbes attract considerable attention as they shelter the largest group of marine microorganisms that are resistant to extreme conditions and can produce novel biogenic substances. Vaccines developed from mangrove microbes may promise a safe future by developing effective immunization procedures with a minimum of economic burden. Interestingly, mangroves offer an exciting opportunity for synthesizing nanoparticles in a greener way as these plants are naturally rich in phytochemicals. Rhizophora mucronata Lam., Avicennia officinalis L. and Excoecaria agallocha L. are capable of synthesizing nanoparticles which have evolved recently as an alternative in various industries and are used for their biomedical application. Besides, the phytoconstituents isolated from mangrove plants, such as: gallic acid, galactose, lupeol, catechins, carotenoids, etc., were explored for various biological activities. These compounds are used in the pharmaceutical and nutraceutical industries to produce antimicrobial, antioxidant, anticancer, antidiabetic, and other therapeutic agents. The present review provides information on the biotechnological potentials of mangrove plants and their bioactive compounds as a new source of novel drugs, enzymes, nanoparticles and therapeutically important microbial pigments. Thus, this review forms a base of support and hasten the urgent research on biomedical applications of mangroves.

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.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.

Secondary metabolites from mangrove-associated fungi: source, chemistry and bioactivities

Covering 1989 to 2020The mangrove forests are a complex ecosystem occurring at tropical and subtropical intertidal estuarine zones and nourish a diverse group of microorganisms including fungi, actinomycetes, bacteria, cyanobacteria, algae, and protozoa. Among the mangrove microbial community, mangrove associated fungi, as the second-largest ecological group of the marine fungi, not only play an essential role in creating and maintaining this biosphere but also represent a rich source of structurally unique and diverse bioactive secondary metabolites, attracting significant attention of organic chemists and pharmacologists. This review summarizes the discovery relating to the source and characteristics of metabolic products isolated from mangrove-associated fungi over the past thirty years (1989-2020). Its emphasis included 1387 new metabolites from 451 papers, focusing on bioactivity and the unique chemical diversity of these natural products.

Bioactive Compounds from Mangrove Endophytic Fungus and Their Uses for Microorganism Control

Mangroves are ecosystems with unique characteristics due to the high salinity and amount of organic matter that house a rich biodiversity. Fungi have aroused much interest as they are an important natural source for the discovery of new bioactive compounds, with potential biotechnological and pharmacological interest. This review aims to highlight endophytic fungi isolated from mangrove plant species and the isolated bioactive compounds and their bioactivity against protozoa, bacteria and pathogenic viruses. Knowledge about this type of ecosystem is of great relevance for its preservation and as a source of new molecules for the control of pathogens that may be of importance for human, animal and environmental health.

Marine natural products

This review covers the literature published between January and December in 2018 for marine natural products (MNPs), with 717 citations (706 for the period January to December 2018) 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 (1554 in 469 papers for 2018), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. The proportion of MNPs assigned absolute configuration over the last decade is also surveyed.

Antibiotics from Extremophilic Micromycetes

Extremophilic microorganisms, which are capable of functioning normally at extremely high or low temperatures, pressure, and in other environmental conditions, have been in the focus of microbiologists' attention for several decades due to the biotechnological potential of enzymes inherent in extremophiles. These enzymes (also called extremozymes) are used in the production of food and detergents and other industries. At the same time, the inhabitants of extreme econiches remained almost unexplored for a long time in terms of the chemistry of natural compounds. In recent years, the emergence of new antibiotic-resistant strains of pathogens, which affect humans and animals has become a global problem. The problem is compounded by a strong slowdown in the development of new antibiotics. In search of new active substances and scaffolds for medical chemistry, researchers turn to unexplored natural sources. In recent years, there has been a sharp increase in the number of studies on secondary metabolites produced by extremophiles. From the discovery of penicillin to the present day, micromycetes, along with actinobacteria, are one of the most productive sources of antibiotic compounds for medicine and agriculture. Many authors consider extremophilic micromycetes as a promising source of small molecules with an unusual mechanism of action or significant structural novelty. This review summarizes the latest (for 2018-2019) experimental data on antibiotic compounds, which are produced by extremophilic micromycetes with various types of adaptation. Active metabolites are classified by the type of structure and biosynthetic origin. The data on the biological activity of the isolated metabolites are summarized.

Mycotoxins as inhibitors of protein tyrosine phosphatases from the deep-sea-derived fungus Aspergillus puniceus SCSIO z021

Nine new xanthone-type and anthraquinone-type mycotoxins including austocystins J-N (1-5), 7-chloro versicolorin A (6), 3'-hydroxy-8-O-methyl versicolorin B (7), 8-O-methyl versiconol (8) and 2',3'-dihydroxy versiconol (9), together with 17 known analogues (10-26) were isolated from an extract of the deep-sea-derived fungus Aspergillus puniceus SCSIO z021. Their structures were elucidated by detailed analysis of spectroscopic data, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra or comparison of the experimental ECD spectra. Eleven hydrogenated austocystins were synthesized from 1-2, 10-15 and 17 by catalytic hydrogenation for bioactivities evaluation. Totally, 18 of the all 37 compounds showed strong toxicity against brine shrimps or Vero cell, and the toxicity of 8-O-methyldemethylsterigmatocystin (18) (LC₅₀ = 0.020 µM) against brine shrimps was higher than those of three positive controls. In addition, 22 of the isolated compounds also exhibited significant inhibitory activity against seven different protein tyrosine phosphatases (PTPs), among them austocystin H (15) and methyl-averantin (24) were the most potent inhibitors with IC₅₀ values of 0.20-3.0 µM. Their structure-bioactivity relationship was also discussed.

Recent progress of antibacterial natural products: Future antibiotics candidates

The discovery of novel antibacterial molecules plays a key role in solving the current antibiotic crisis issue. Natural products have long been an important source of drug discovery. Herein, we reviewed 256 natural products from 11 structural classes in the period of 2016-01/2020, which were selected by SciFinder with new compounds or new structures and MICs lower than 10 μg/mL or 10 μM as criterions. This review will provide some effective antibacterial lead compounds for medicinal chemists, which will promote the antibiotics research based on natural products to the next level.

Overview on antibacterial metabolites from terrestrial Aspergillus spp

Medicines developed from natural sources are a frequent target for the research and discovery of antimicrobial compounds. Discovering of penicillin in 1928 was a motive to explore of nature as a source of new antimicrobial agents. Fungi produce a diverse range of bioactive metabolites, making them rich source of different types of medicines. The purpose of this paper was to review studies on antibacterials from terrestrial Aspergillus published exclusively during 1942-2018, with emphasis on their antibacterial activities, structures, and mechanisms of action if present. According to the results from different studies in the world, large number of compounds and extracts showed different activities against different bacterial species, including Gram-positive and Gram-negative bacteria. The most prominent result was that of the compound CJ-17,665, isolated from A. ochraceus, showing good activity against multi-drug resistant Staphylococcus aureus, which is well-recognised to be one of the most important current public health problem. These findings may motivate scientists to undertake a project that may result in the development of novel antibacterial drugs from terrestrial-derived Aspergillus spp., although further toxicity assays (in vivo) must be performed before their application.