Selected Fungal Natural Products with Antimicrobial Properties

Carbon-Dots-Mediated Improvement of Antimicrobial Activity of Natural Products

The development of new microbicidal compounds has become a top priority due to the emergence and spread of drug-resistant pathogenic microbes. In this study, blue-emitting and positively charged carbon dots (CDs), called Du-CDs, were fabricated for the first time utilizing the natural product extract of endophyte Diaporthe unshiuensis YSP3 as raw material through a one-step solvothermal method, which possessed varied functional groups including amino, carboxyl, hydroxyl, and sulfite groups. Interestingly, Du-CDs exhibited notably enhanced antimicrobial activities toward both bacteria and fungi as compared to the natural product extract of YSP3, with low minimum inhibitory concentrations. Moreover, Du-CDs significantly inhibited the formation of biofilms. Du-CDs bound with the microbial cell surface via electronic interaction or hydrophobic interaction entered the microbial cells and were distributed fully inside the cells. Du-CDs caused cell membrane damage and/or cell division cycle interruption, resulting in microbial cell death. Moreover, Du-CDs exhibited an improved antimicrobial effect and accelerated wound healing ability with good biocompatibility in the mouse model. Overall, we demonstrate that the formation of CDs from fungal natural products presents a promising and potential means to develop novel antimicrobial agents with great fluorescence, improved microbiocidal effect and wound healing capacity, and good biosafety for combating microbial infections.

Unveiling Drimenol: A Phytochemical with Multifaceted Bioactivities

Drimenol, a phytochemical with a distinct odor is found in edible aromatic plants, such as Polygonum minus (known as kesum in Malaysia) and Drimys winteri. Recently, drimenol has received increasing attention owing to its diverse biological activities. This review offers the first extensive overview of drimenol, covering its sources, bioactivities, and derivatives. Notably, drimenol possesses a wide spectrum of biological activities, including antifungal, antibacterial, anti-insect, antiparasitic, cytotoxic, anticancer, and antioxidant effects. Moreover, some mechanisms of its activities, such as its antifungal effects against human mycoses and anticancer activities, have been investigated. However, there are still several crucial issues in the research on drimenol, such as the lack of experimental understanding of its pharmacokinetics, bioavailability, and toxicity. By synthesizing current research findings, this review aims to present a holistic understanding of drimenol, paving the way for future studies and its potential utilization in diverse fields.

Wild Mushrooms as a Source of Bioactive Compounds and Their Antioxidant Properties-Preliminary Studies

The aim of this study was to preliminarily determine the content of bioactive components in the fruiting bodies of four previously unstudied mushroom species: Aleuria aurantia, Phallus hadriani, Phanus conchatus, Geastrum pectinatum, their antioxidant activity and the content of polyphenols, minerals and heavy metals.

METHODS

Determination of active compounds by gas chromatography-mass spectrometry was carried out in addition to thermogravimetric determinations, quantitative determination of total polyphenols by spectrophotometry using Folin-Ciocalteu reagent, determination of antioxidant activity using 2,2-diphenyl-1-picryl hydrazyl radical (DPPH) and 2,2'-azino-di-[3-ethylbentiazoline sulphonated] (ATBS). In addition, spectrometric analysis of selected minerals and heavy metals was performed by inductively coupled plasma optical emission spectroscopy (ICP-OES).

RESULTS

The mushrooms analysed varied in terms of their bioactive constituents. They contained components with varying effects on human health, including fatty acids, oleamide, 1,2-dipalmitoylglycerol, (2-phenyl-1,3-dioxolan-4-yl)-methyl ester of oleic acid, deoxyspergualin, 2-methylenocholestan-3-ol, hexadecanoamide, isoallochan, 2,6-diaminopurine, and adenine. All contained polyphenols and varying amounts of minerals (calcium, magnesium, iron, zinc, potassium, phosphorus, sodium, copper, silicon and manganese) and exhibited antioxidant properties of varying potency. No exceedances of the permissible concentration of lead and cadmium were observed in any of them.

CONCLUSIONS

All of the mushrooms studied can provide material for the extraction of various bioactive compounds with physiological effects. In addition, the presence of polyphenols and minerals, as well as antioxidant properties and the absence of exceeding the permissible concentration of heavy metals, indicate that these species could be interesting material in the design of foods with health-promoting properties, nutraceuticals or dietary supplements. However, the use of the fruiting bodies of these mushrooms requires mandatory toxicological and clinical studies.

Diversity of endophytic bacteria with antimicrobial potential isolated from marine macroalgae from Yacila and Cangrejos beaches, Piura-Peru

Endophytic bacteria found in marine macroalgae have been studied for their potential antimicrobial activity, consequently, they could serve as a valuable source of bioactive compounds to control pathogenic bacteria, yeasts, and fungi. Algae endophytic bacteria were isolated from Caulerpa sp., Ulva sp., Ahnfeltiopsis sp., and Chondracantus chamissoi from Yacila and Cangrejo Beaches (Piura, Peru). Antimicrobial assays against pathogenic bacteria were evaluated using cross-culture, over-plate, and volatile organic compound tests. Afterward, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of selected crude extracts were determined, also ITS molecular analysis, antifungal activity, and PCR of iturin, fengycin, and surfactin genes were performed for bacteria strains exhibiting better activity. Forty-six algae endophytic bacteria were isolated from algae. Ten strains inhibited gram-positive pathogenic bacteria (Enterococcus faecalis, Staphylococcus epidermidis, S. aureus, and Listeria monocytogenes), and 12 inhibited gram-negative bacteria (Escherichia coli and Salmonella enteric sv typhimurium). Bacteria with better activity belong to Bacillus sp., Kluyvera ascorbata, Pantoea agglomerans, Leclercia adecarboxylata, and Enterobacter sp., which only four showed antifungal activities against Candida albicans, C. tropicalis, Colletotrichium sp., Fusarium sp., Fusarium oxysporum, and Alternaria sp. Furthermore, K. ascorbata YAFE21 and Bacillus sp. YCFE4 exhibited iturin and fengycin genes. The results indicate that the algae endophytic bacteria found in this study, particularly K. ascorbata YAFE21, Bacillus sp. YCFR6, L. adecarboxylata CUFE2, Bacillus sp. YUFE8, Enterobacter sp. YAFL1, and P. agglomerans YAFL6, could be investigated as potential producers of antimicrobial compounds due to their broad activity against various microorganisms.

Mycoproteins and their health-promoting properties: Fusarium species and beyond

Filamentous fungal mycoproteins have gained increasing attention as sustainable alternatives to animal and plant-based proteins. This comprehensive review summarizes the nutritional characteristics, toxicological aspects, and health-promoting effects of mycoproteins, focusing on those derived from filamentous fungi, notably Fusarium venenatum. Mycoproteins are characterized by their high protein content, and they have a superior essential amino acid profile compared to soybeans indicating excellent protein quality and benefits for human nutrition. Additionally, mycoproteins offer enhanced digestibility, further highlighting their suitability as a protein source. Furthermore, mycoproteins are rich in dietary fibers, which have been associated with health benefits, including protection against metabolic diseases. Moreover, their fatty acids profile, with significant proportions of polyunsaturated fatty acids and absence of cholesterol, distinguishes them from animal-derived proteins. In conclusion, the future of mycoproteins as a health-promoting protein alternative and the development of functional foods relies on several key aspects. These include improving the acceptance of mycoproteins, conducting further research into their mechanisms of action, addressing consumer preferences and perceptions, and ensuring safety and regulatory compliance. To fully unlock the potential of mycoproteins and meet the evolving needs of a health-conscious society, continuous interdisciplinary research, collaboration among stakeholders, and proactive engagement with consumers will be vital.

Targeting Fks1 proteins for novel antifungal drug discovery

Fungal infections are a major threat to human health. The limited availability of antifungal drugs, the emergence of drug resistance, and a growing susceptible population highlight the critical need for novel antifungal agents. The enzymes involved in fungal cell wall synthesis offer potential targets for antifungal drug development. Recent studies have enhanced our focus on the enzyme Fks1, which synthesizes β-1,3-glucan, a critical component of the cell wall. These studies provide a deeper understanding of Fks1's function in cell wall biosynthesis, pathogenicity, structural biology, evolutionary conservation across fungi, and interaction with current antifungal drugs. Here, we discuss the role of Fks1 in the survival and adaptation of fungi, guided by insights from evolutionary and structural analyses. Furthermore, we delve into the dynamics of Fks1 modulation with novel antifungal strategies and assess its potential as an antifungal drug target.

A review on endophytic fungi: a potent reservoir of bioactive metabolites with special emphasis on blight disease management

Phytopathogenic microorganisms have caused blight diseases that present significant challenges to global agriculture. These diseases result in substantial crop losses and have a significant economic impact. Due to the limitations of conventional chemical treatments in effectively and sustainably managing these diseases, there is an increasing interest in exploring alternative and environmentally friendly approaches for disease control. Using endophytic fungi as biocontrol agents has become a promising strategy in recent years. Endophytic fungi live inside plant tissues, forming mutually beneficial relationships, and have been discovered to produce a wide range of bioactive metabolites. These metabolites demonstrate significant potential for fighting blight diseases and provide a plentiful source of new biopesticides. In this review, we delve into the potential of endophytic fungi as a means of biocontrol against blight diseases. We specifically highlight their significance as a source of biologically active compounds. The review explores different mechanisms used by endophytic fungi to suppress phytopathogens. These mechanisms include competing for nutrients, producing antifungal compounds, and triggering plant defense responses. Furthermore, this review discusses the challenges of using endophytic fungi as biocontrol agents in commercial applications. It emphasizes the importance of conducting thorough research to enhance their effectiveness and stability in real-world environments. Therefore, bioactive metabolites from endophytic fungi have considerable potential for sustainable and eco-friendly blight disease control. Additional research on endophytes and their metabolites will promote biotechnology solutions.

Comprehensive review of clean-label antimicrobials used in dairy products

Consumers expect safe, healthy, natural, and sustainable food. Within the food industry, ingredient use is changing due to these consumer demands. While no single agreed-upon definition of clean label exists, a "clean label" in the context of food refers to a product that has a simplified and transparent ingredient list, with easily recognizable and commonly understood components to the general public. Clean-label products necessitate and foster a heightened level of transparency between companies and consumers. Dairy products are vulnerable to being contaminated by both pathogens and spoilage microorganisms. These microorganisms can be effectively controlled by replacing conventional antimicrobials with clean-label ingredients such as protective cultures or bacterial/fungal fermentates. This review summarizes the perspectives of consumers and the food industry regarding the definition of "clean label," and the current and potential future use of clean-label antimicrobials in dairy products. A key goal of this review is to make the concept of clean-label antimicrobial agents better understood by both manufacturers and researchers.

Antifungal Activities of Natural Products and Their Hybrid Molecules

The increasing cases of drug resistance and high toxicity associated with the currently used antifungal agents are a worldwide public health concern. There is an urgent need to develop new antifungal drugs with unique target mechanisms. Plant-based compounds, such as carvacrol, eugenol, coumarin, cinnamaldehyde, curcumin, thymol, etc., have been explored for the development of promising antifungal agents due to their diverse biological activities, lack of toxicity, and availability. However, researchers around the world are unable to fully utilize the potential of natural products due to limitations, such as their poor bioavailability and aqueous solubility. The development of hybrid molecules containing natural products is a promising synthetic approach to overcome these limitations and control microbes' capability to develop resistance. Based on the potential advantages of hybrid compounds containing natural products to improve antifungal activity, there have been different reported synthesized hybrid compounds. This paper reviews different literature to report the potential antifungal activities of hybrid compounds containing natural products.

Natural Compounds of Fungal Origin with Antimicrobial Activity-Potential Cosmetics Applications

The phenomenon of drug resistance in micro-organisms necessitates the search for new compounds capable of combating them. Fungi emerge as a promising source of such compounds as they produce a wide range of secondary metabolites with bacteriostatic or fungistatic activity. These compounds can serve as alternatives for commonly used antibiotics. Furthermore, fungi also accumulate compounds with antiviral activity. This review focuses on filamentous fungi and macrofungi as sources of antimicrobial compounds. The article describes both individual isolated compounds and extracts that exhibit antibacterial, antifungal, and antiviral activity. These compounds are produced by the fruiting bodies and mycelium, as well as the biomass of mycelial cultures. Additionally, this review characterizes the chemical compounds extracted from mushrooms used in the realm of cosmetology; specifically, their antimicrobial activity.

The Cytotoxic Properties of Extreme Fungi's Bioactive Components-An Updated Metabolic and Omics Overview

Fungi are the most diverse living organisms on planet Earth, where their ubiquitous presence in various ecosystems offers vast potential for the research and discovery of new, naturally occurring medicinal products. Concerning human health, cancer remains one of the leading causes of mortality. While extensive research is being conducted on treatments and their efficacy in various stages of cancer, finding cytotoxic drugs that target tumor cells with no/less toxicity toward normal tissue is a significant challenge. In addition, traditional cancer treatments continue to suffer from chemical resistance. Fortunately, the cytotoxic properties of several natural products derived from various microorganisms, including fungi, are now well-established. The current review aims to extract and consolidate the findings of various scientific studies that identified fungi-derived bioactive metabolites with antitumor (anticancer) properties. The antitumor secondary metabolites identified from extremophilic and extremotolerant fungi are grouped according to their biological activity and type. It became evident that the significance of these compounds, with their medicinal properties and their potential application in cancer treatment, is tremendous. Furthermore, the utilization of omics tools, analysis, and genome mining technology to identify the novel metabolites for targeted treatments is discussed. Through this review, we tried to accentuate the invaluable importance of fungi grown in extreme environments and the necessity of innovative research in discovering naturally occurring bioactive compounds for the development of novel cancer treatments.

Phoma spp. an untapped treasure of cytotoxic compounds: current status and perspectives

The genus Phoma has been explored for a wide range of secondary metabolites signifying a huge range of bioactivities. Phoma sensu lato is a major group that secretes several secondary metabolites. The genus Phoma mainly includes Phoma macrostoma, P. multirostrata, P. exigua, P. herbarum, P. betae, P. bellidis, P. medicaginis, P. tropica, and many more species from the genus that are continuously being identified for their potential secondary metabolites. The metabolite spectrum includes bioactive compounds like phomenon, phomin, phomodione, cytochalasins, cercosporamide, phomazines, and phomapyrone reported from various Phoma spp. These secondary metabolites show a broad range of activities including antimicrobial, antiviral, antinematode, and anticancer. The present review is aimed to emphasize the importance of Phoma sensu lato fungi, as a natural source of biologically active secondary metabolites, and their cytotoxic activities. So far, cytotoxic activities of Phoma spp. have not been reviewed; hence, this review will be novel and useful for the readers to develop Phoma-derived anticancer agents. KEY POINTS: • Different Phoma spp. contain a wide variety of bioactive metabolites. • These Phoma spp. also secrete cytotoxic and antitumor compounds. • The secondary metabolites can be used for the development of anticancer agents.

Current Insights in Fungal Importance-A Comprehensive Review

Besides plants and animals, the Fungi kingdom describes several species characterized by various forms and applications. They can be found in all habitats and play an essential role in the excellent functioning of the ecosystem, for example, as decomposers of plant material for the cycling of carbon and nutrients or as symbionts of plants. Furthermore, fungi have been used in many sectors for centuries, from producing food, beverages, and medications. Recently, they have gained significant recognition for protecting the environment, agriculture, and several industrial applications. The current article intends to review the beneficial roles of fungi used for a vast range of applications, such as the production of several enzymes and pigments, applications regarding food and pharmaceutical industries, the environment, and research domains, as well as the negative impacts of fungi (secondary metabolites production, etiological agents of diseases in plants, animals, and humans, as well as deteriogenic agents).

LaeA-Regulated Fungal Traits Mediate Bacterial Community Assembly

Potent antimicrobial metabolites are produced by filamentous fungi in pure culture, but their ecological functions in nature are often unknown. Using an antibacterial Penicillium isolate and a cheese rind microbial community, we demonstrate that a fungal specialized metabolite can regulate the diversity of bacterial communities. Inactivation of the global regulator, LaeA, resulted in the loss of antibacterial activity in the Penicillium isolate. Cheese rind bacterial communities assembled with the laeA deletion strain had significantly higher bacterial abundances than the wild-type strain. RNA-sequencing and metabolite profiling demonstrated a striking reduction in the expression and production of the natural product pseurotin in the laeA deletion strain. Inactivation of a core gene in the pseurotin biosynthetic cluster restored bacterial community composition, confirming the role of pseurotins in mediating bacterial community assembly. Our discovery demonstrates how global regulators of fungal transcription can control the assembly of bacterial communities and highlights an ecological role for a widespread class of fungal specialized metabolites. IMPORTANCE Cheese rinds are economically important microbial communities where fungi can impact food quality and aesthetics. The specific mechanisms by which fungi can regulate bacterial community assembly in cheeses, other fermented foods, and microbiomes in general are largely unknown. Our study highlights how specialized metabolites secreted by a Penicillium species can mediate cheese rind development via differential inhibition of bacterial community members. Because LaeA regulates specialized metabolites and other ecologically relevant traits in a wide range of filamentous fungi, this global regulator may have similar impacts in other fungus-dominated microbiomes.

Discovery of a gene cluster for the biosynthesis of novel cyclic peptide compound, KK-1, in Curvularia clavata

KK-1, a cyclic depsipeptide with 10 residues produced by a filamentous fungus Curvularia clavata BAUA-2787, is a promising pesticide active compound with high activity against many plant pathogens, especially Botrytis cinerea. As a first step toward the future mass production of KK-1 through synthetic biological approaches, we aimed to identify the genes responsible for the KK-1 biosynthesis. To achieve this, we conducted whole genome sequencing and transcriptome analysis of C. clavata BAUA-2787 to predict the KK-1 biosynthetic gene cluster. We then generated the overexpression and deletion mutants for each cluster gene using our originally developed transformation system for this fungus, and analyzed the KK-1 production and the cluster gene expression levels to confirm their involvement in KK-1 biosynthesis. As a result of these, a region of approximately 71 kb was found, containing 10 open reading frames, which were co-induced during KK-1 production, as a biosynthetic gene cluster. These include kk1B, which encodes nonribosomal peptide synthetase with a domain structure that is consistent with the structural features of KK-1, and kk1F, which encodes a transcription factor. The overexpression of kk1F increased the expression of the entire cluster genes and, consequently, improved KK-1 production, whereas its deletion decreased the expression of the entire cluster genes and almost eliminated KK-1 production, demonstrating that the protein encoded by kk1F regulates the expressions of the other nine cluster genes cooperatively as the pathway-specific transcription factor. Furthermore, the deletion of each cluster gene caused a reduction in KK-1 productivity, indicating that each gene is involved in KK-1 production. The genes kk1A, kk1D, kk1H, and kk1I, which showed a significant decrease in KK-1 productivity due to deletion, were presumed to be directly involved in KK-1 structure formation, including the biosynthesis of the constituent residues. kk1C, kk1E, kk1G, and kk1J, which maintained a certain level of KK-1 productivity despite deletion, were possibly involved in promoting or assisting KK-1 production, such as extracellular transportation and the removal of aberrant units incorporated into the peptide chain.

Deterministic Effect of pH on Shaping Soil Resistome Revealed by Metagenomic Analysis

Soil is recognized as the major reservoir of antibiotic resistance genes (ARGs), harboring the most diverse naturally evolved ARGs on the planet. Multidrug resistance genes are a class of ARGs, and their high prevalence in natural soil ecosystems has recently raised concerns. Since most of these genes express proton motive force (PMF) driven efflux pumps, studying whether soil pH is a determinant for the selection of multidrug efflux pump genes and thus shaping the soil resistome are of great interest. In this study, we collected 108 soils with pH values ranging from 4.37 to 9.69 from multiple ecosystems and profiled the composition of ARGs for metagenomes and metagenome-assembled genomes. We observed the multidrug efflux pump genes enriched in the acidic soil resistome, and their abundances have significant soil pH dependence. This reflects the benefits of high soil proton activity on the multidrug efflux pump genes, especially for the PMF-driven inner membrane transferase. In addition, we preliminary indicate the putative microbial participants in pH shaping the soil resistome by applying ecological analyzing tools such as stepwise regression and random forest model fitting. The decisive influence of proton activity on shaping the resistome is more impactful than any other examined factors, and as the consequence, we revisited the influence of edaphic factors on the soil resistome; i.e., the deterministic selection of resistance mechanisms by edaphic factors could lead to the bottom-up shaping of the ARG composition. Such natural developing mechanisms of the resistome are herein suggested to be considered in assessing human-driven ARG transmissions.

Small molecules containing chalcogen elements (S, Se, Te) as new warhead to fight neglected tropical diseases

Neglected tropical diseases (NTDs) encompass a group of infectious diseases with a protozoan etiology, high incidence, and prevalence in developing countries. As a result, economic factors constitute one of the main obstacles to their management. Endemic countries have high levels of poverty, deprivation and marginalization which affect patients and limit their access to proper medical care. As a matter of fact, statistics remain uncollected in some affected areas due to non-reporting cases. World Health Organization and other organizations proposed a plan for the eradication and control of the vector, although many of these plans were halted by the COVID-19 pandemic. Despite of the available drugs to treat these pathologies, it exists a lack of effectiveness against several parasite strains. Treatment protocols for diseases such as American trypanosomiasis (Chagas disease), leishmaniasis, and human African trypanosomiasis (HAT) have not achieved the desired results. Unfortunately, these drugs present limitations such as side effects, toxicity, teratogenicity, renal, and hepatic impairment, as well as high costs that have hindered the control and eradication of these diseases. This review focuses on the analysis of a collection of scientific shreds of evidence with the aim of identifying novel chalcogen-derived molecules with biological activity against Chagas disease, leishmaniasis and HAT. Compounds illustrated in each figure share the distinction of containing at least one chalcogen element. Sulfur (S), selenium (Se), and tellurium (Te) have been grouped and analyzed in accordance with their design strategy, chemical synthesis process and biological activity. After an exhaustive revision of the related literature on S, Se, and Te compounds, 183 compounds presenting excellent biological performance were gathered against the different causative agents of CD, leishmaniasis and HAT.

Screening of Antimicrobial Properties and Bioactive Compounds of Pleurotus Ostreatus Extracts against Staphylococcus Aureus, Escherichia coli, and Neisseria Gonorrhoeae

In recent years, the potential of pathogenic bacteria to acquire resistance to a variety of antimicrobial drugs has developed significantly due to the indiscriminate exposure of a number of antibiotic compounds. The purpose of this study is to determine the antibacterial capabilities and activities of crude Pleurotus ostreatus extracts against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Neisseria gonorrhoeae (ATCC 49926), and nine multidrug-resistant clinical isolates of Neisseria gonorrhoeae. All of these isolates exhibited sensitivity to azithromycin and ceftriaxone, while the majority of antibiotic resistance was seen against penicillin G, sulphonamide, and ciprofloxacin. Fifty percent of the isolates exhibited absolute resistance to both sulphonamide and ciprofloxacin, whereas 40% of the isolates displayed absolute resistance to penicillin G. The antibacterial activity of P. ostreatus extracts examined in this investigation varied within the same species of microorganisms. Extract B and D, extracted in the presence of 20% wheat bran bagasse and 20% maize flour bagasse, respectively, had exceptional antibacterial activity against all target isolates examined. We observed the lowest concentration of antibacterial agent required to inhibit the target bacteria to be between 1 × 10^-3 mg/ml and 1 × 10^-6 mg/ml with an estimated probability of 0.30769, a lower 95% confidence interval (CI) of 0.126807, an upper 95% CI of 0.576307, an estimated probability of 0.15385, a lower 95% CI of 0.043258, and an upper 95% CI, respectively. The MBC of 1 × 10^-3 mg/ml was seen to eliminate 31% of the target bacteria. This dose was the most inhibitive. The antibacterial activity of all the extracts examined in the current study exhibited some degree of efficacy against both clinical isolates and standard strains. However, the majority of clinically isolated bacteria exhibited greater resistance to the extracts.

Innovative Strategies to Overcome Antimicrobial Resistance and Tolerance

Antimicrobial resistance and tolerance are natural phenomena that arose due to evolutionary adaptation of microorganisms against various xenobiotic agents. These adaptation mechanisms make the current treatment options challenging as it is increasingly difficult to treat a broad range of infections, associated biofilm formation, intracellular and host adapted microbes, as well as persister cells and microbes in protected niches. Therefore, novel strategies are needed to identify the most promising drug targets to overcome the existing hurdles in the treatment of infectious diseases. Furthermore, discovery of novel drug candidates is also much needed, as few novel antimicrobial drugs have been introduced in the last two decades. In this review, we focus on the strategies that may help in the development of innovative small molecules which can interfere with microbial resistance mechanisms. We also highlight the recent advances in optimization of growth media which mimic host conditions and genome scale molecular analyses of microbial response against antimicrobial agents. Furthermore, we discuss the identification of antibiofilm molecules and their mechanisms of action in the light of the distinct physiology and metabolism of biofilm cells. This review thus provides the most recent advances in host mimicking growth media for effective drug discovery and development of antimicrobial and antibiofilm agents.

The vital role of animal, marine, and microbial natural products against COVID-19

CONTEXT

Since the outbreak of SARS-CoV-2, researchers have been working on finding ways to prevent viral entry and pathogenesis. Drug development from naturally-sourced pharmacological constituents may be a fruitful approach to COVID-19 therapy.

OBJECTIVE

Most of the published literature has focussed on medicinal plants, while less attention has been given to biodiverse sources such as animal, marine, and microbial products. This review focuses on highlighting natural products and their derivatives that have been evaluated for antiviral, anti-inflammatory, and immunomodulatory properties.

METHODS

We searched electronic databases such as PubMed, Scopus, Science Direct and Springer Link to gather raw data from publications up to March 2021, using terms such as 'natural products', marine, micro-organism, and animal, COVID-19. We extracted a number of documented clinical trials of products that were tested in silico, in vitro, and in vivo which paid specific attention to chemical profiles and mechanisms of action.

RESULTS

Various classes of flavonoids, 2 polyphenols, peptides and tannins were found, which exhibit inhibitory properties against viral and host proteins, including 3CLpro, PLpro, S, hACE2, and NF-κB, many of which are in different phases of clinical trials.

DISCUSSION AND CONCLUSIONS

The synergistic effects of logical combinations with different mechanisms of action emphasizes their value in COVID19 management, such as iota carrageenan nasal spray, ermectin oral drops, omega-3 supplementation, and a quadruple treatment of zinc, quercetin, bromelain, and vitamin C. Though in vivo efficacy of these compounds has yet to be established, these bioproducts are potentially useful in counteracting the effects of SARS-CoV-2.

Antiviral Potential of Natural Resources against Influenza Virus Infections

Influenza is a severe contagious disease caused by influenza A and B viruses. The WHO estimates that annual outbreaks lead to 3-5 million severe infections of which approximately 10% lead to the death of the patient. While vaccination is the cornerstone of prevention, antiviral drugs represent the most important treatment option of acute infections. Only two classes of drugs are currently approved for the treatment of influenza in numerous countries: M2 channel blockers and neuraminidase inhibitors. In some countries, additional compounds such as the recently developed cap-dependent endonuclease inhibitor baloxavir marboxil or the polymerase inhibitor favipiravir are available. However, many of these compounds suffer from poor efficacy, if not applied early after infection. Furthermore, many influenza strains have developed resistances and lost susceptibility to these compounds. As a result, there is an urgent need to develop new anti-influenza drugs against a broad spectrum of subtypes. Natural products have made an important contribution to the development of new lead structures, particularly in the field of infectious diseases. Therefore, this article aims to review the research on the identification of novel lead structures isolated from natural resources suitable to treat influenza infections.

Fluorinated derivatives of tetrahydroaltersolanol molecule on COVID-19, HIV, and HTLV protease by DFT and molecular docking approaches

Structural, optoelectronic, and biological properties of tetrahydroaltersolanol (C₁₆H₂₀O₇) and fluorinated derivatives are calculated using density functional theory (DFT) and molecular docking approaches. It is shown that the pure C₁₆H₂₀O₇ molecule has a direct HOMO-LUMO energy gap about 3.1 eV. The substitution of F atom at A category decreases the electronic energy gap, while it is constant at B category. In A category, the behavior of the pure molecule changed from insulator to semiconductor with various substitution of F atom. The electronic properties were depended on the F sites in the pure molecule. The molecular electrical transport properties and charge-transfer possibilities increase with decreasing energy gap. The pure C₁₆H₂₀O₇ molecule with high energy gap has low chemical reactivity and substitution of F atom at considered molecule increases chemical reactivity. Obtained results show that F-O bonds in trifurcation bonds of C₁₆H₁₉O₇(F14), C₁₆H₁₉O₇(F16), and C₁₆H₁₉O₇(F17) molecules play a key role in confronting with COVID-19, HIV, and HTLV proteases, respectively. Optical spectra, such as the dielectric functions, electron energy-loss spectroscopy, refractive index, extinction coefficient, and reflection spectra show that fluorinated derivatives of C₁₆H₂₀O₇ at B category can be used in the new drugs.

Microbial cooperation promotes humification to reduce antibiotic resistance genes abundance in food waste composting

Antibiotic resistance genes (ARGs) fate in a full-scale Food waste (FW) facility was investigated. Results showed that with the changes in ARGs, microbial networks could be naturally divided into two clusters, named as the ARGs increasing group (AI group) and the ARGs decreasing group (AD group). The significant difference between two groups (i.e. stronger microbial competition in the AI group and stronger microbial cooperation in the AD group) implied that the variation in ARGs over time were caused by a switch between competition and cooperation. These results indicated that microbial competition might increase ARGs abundance, while cooperation might reduce it. Meanwhile, structural-equation-model (SEM model) showed that humification indexes (e.g. GI value) was an indicator for characterizing microbial interactions and ARGs. The results of the linear model further confirmed that mature compost (GI values > 92.6 %) could reduce the risk of ARGs.

Engineering plant family TPS into cyanobacterial host for terpenoids production

Terpenoids are synthesized naturally by plants as secondary metabolites, and are diverse and complex in structure with multiple applications in bioenergy, food, cosmetics, and medicine. This makes the production of terpenoids such as isoprene, β-phellandrene, farnesene, amorphadiene, and squalene valuable, owing to which their industrial demand cannot be fulfilled exclusively by plant sources. They are synthesized via the Methylerythritol phosphate pathway (MEP) and the Mevalonate pathway (MVA), both existing in plants. The advent of genetic engineering and the latest accomplishments in synthetic biology and metabolic engineering allow microbial synthesis of terpenoids. Cyanobacteria manifest to be the promising hosts for this, utilizing sunlight and CO2. Cyanobacteria possess MEP pathway to generate precursors for terpenoid synthesis. The terpenoid synthesis can be amplified by overexpressing the MEP pathway and engineering MVA pathway genes. According to the desired terpenoid, terpene synthases unique to the plant kingdom must be incorporated in cyanobacteria. Engineering an organism to be used as a cell factory comes with drawbacks such as hampered cell growth and disturbance in metabolic flux. This review set forth a comparison between MEP and MVA pathways, strategies to overexpress these pathways with their challenges.

Microbial Metabolites Beneficial to Plant Hosts Across Ecosystems

Plants are intimately connected with their associated microorganisms. Chemical interactions via natural products between plants and their microbial symbionts form an important aspect in host health and development, both in aquatic and terrestrial ecosystems. These interactions range from negative to beneficial for microbial symbionts as well as their hosts. Symbiotic microbes synchronize their metabolism with their hosts, thus suggesting a possible coevolution among them. Metabolites, synthesized from plants and microbes due to their association and coaction, supplement the already present metabolites, thus promoting plant growth, maintaining physiological status, and countering various biotic and abiotic stress factors. However, environmental changes, such as pollution and temperature variations, as well as anthropogenic-induced monoculture settings, have a significant influence on plant-associated microbial community and its interaction with the host. In this review, we put the prominent microbial metabolites participating in plant-microbe interactions in the natural terrestrial and aquatic ecosystems in a single perspective and have discussed commonalities and differences in these interactions for adaptation to surrounding environment and how environmental changes can alter the same. We also present the status and further possibilities of employing chemical interactions for environment remediation. Our review thus underlines the importance of ecosystem-driven functional adaptations of plant-microbe interactions in natural and anthropogenically influenced ecosystems and their possible applications.

Investigation of Morchella esculenta and Morchella conica for their antibacterial potential against methicillin-susceptible Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Streptococcus pyogenes

Antimicrobial resistance is an alarming problem, especially due to emergence of methicillin-resistance Staphylococcus aureus (MRSA). World Health Organization (WHO) has already listed MRSA as a top priority pathogen for the development of novel antibacterial agents. Presently, different therapeutic approaches against bacterial infections are in practice which includes targeting bacterial virulence factors, bacteriophage therapy, and manipulation of the microbiome. Natural products have been efficiently used for centuries to combat bacterial infections. Morchella is a natural fungal product which has been reported to possess broad-spectrum biological activities against bacterial infections. Hence, this study was aimed to evaluate the antibacterial efficacy of two macro-fungi against S. aureus, MRSA, and Streptococcus pyogenes (S. pyogenes). The antibacterial potential of both fungal extracts (Morchella esculenta and Morchella conica) was evaluated using disk diffusion and standard broth microdilution methods. The chemical compounds of both fungi were investigated using ultra-performance liquid chromatography mass spectroscopy (UPLC-MS) analysis. All fungal extracts inhibited growth of tested bacteria with inhibitory zone ranging from 10.66 ± 0.3 to 21.00 ± 1.5 mm. The minimum inhibitory concentration (MIC) of tested bacterial growth ranged from 03.33 to 16.0 mg/ml. It was noteworthy that Morchella extracts prevented S. aureus growth in a bactericidal manner with minimal bactericidal concentration (MBC) of 8-16 mg/ml. The extracts were also more effective against MRSA than currently available antibiotics. In conclusion, the growth inhibition of tested bacteria by fungal extracts revealed their potential as antibacterial agents and their compounds may be used as drug candidates.

Molecular docking analysis of long-chain alkanes with the β-lactamase BEL-1 from P. aeruginosa

Pseudomonas aeruginosa is a gram-negative opportunistic bacterium that is a concern worldwide due to its innate antibiotic resistance properties. This warrants the development of non-antibiotic compounds that can potentially address the growing concern. Therefore, it is of interest to document the molecular docking analysis data of three long-chain alkanes, namely, eicosane, triacontane, and nonadecane with β-lactamase BEL-1. Data shows that nonadecane have good binding features and drug-likeness when compared to triacontane and nonadecane. It is well known that nonadecane is a compound that is abundantly available from natural resources for further consideration.

Fungal-derived compounds and mycogenic nanoparticles with antimycobacterial activity: a review

Tuberculosis (TB) is a persistent lung infection caused by Mycobacterium tuberculosis. The disease is characterized by high mortality rates of over 1 million per year. Unfortunately, the potency and effectiveness of currently used anti-TB drugs is gradually decreasing due to the constant development of persistence and resistance by M. tuberculosis. The adverse side effects associated with current anti-TB drugs, along with anti-TB drug resistance, present an opportunity to bio-prospect novel potent anti-TB drugs from unique sources. Fundamentally, fungi are a rich source of bioactive secondary metabolites with valuable therapeutic potential. Enhancing the potency and effectiveness of fungal-based anti-TB drug leads by chemical synthesis and/or modification with nanomaterials, may result in the discovery of novel anti-TB drugs. In this review, the antimycobacterial activity of fungal-derived compounds and mycogenic nanoparticles are summarized. Numerous fungal-derived compounds as well as some mycogenic nanoparticles that exhibit strong antimycobacterial activity that is comparable to that of approved drugs, were found. If fully explored, fungi holds the promise to become key drivers in the generation of lead compounds in TB-drug discovery initiatives.

Biosynthesis of Rubellins in Ramularia collo-cygni-Genetic Basis and Pathway Proposition

The important disease Ramularia leaf spot of barley is caused by the fungus Ramularia collo-cygni. The disease causes yield and quality losses as a result of a decrease in photosynthesis efficiency due to the appearance of necrotic spots on the leaf surface. The development of these typical Ramularia leaf spot symptoms is thought to be linked with the release of phytotoxic secondary metabolites called rubellins in the host. However, to date, neither the biosynthetic pathways leading to the production of these metabolites nor their exact role in disease development are known. Using a combined in silico genetic and biochemistry approach, we interrogated the genome of R. collo-cygni to identify a putative rubellin biosynthetic gene cluster. Here we report the identification of a gene cluster containing homologues of genes involved in the biosynthesis of related anthraquinone metabolites in closely related fungi. A putative pathway to rubellin biosynthesis involving the genes located on the candidate cluster is also proposed.

Fungal Endophytes: A Potential Source of Antibacterial Compounds

Antibiotic resistance is becoming a burning issue due to the frequent use of antibiotics for curing common bacterial infections, indicating that we are running out of effective antibiotics. This has been more obvious during recent corona pandemics. Similarly, enhancement of antimicrobial resistance (AMR) is strengthening the pathogenicity and virulence of infectious microbes. Endophytes have shown expression of various new many bioactive compounds with significant biological activities. Specifically, in endophytic fungi, bioactive metabolites with unique skeletons have been identified which could be helpful in the prevention of increasing antimicrobial resistance. The major classes of metabolites reported include anthraquinone, sesquiterpenoid, chromone, xanthone, phenols, quinones, quinolone, piperazine, coumarins and cyclic peptides. In the present review, we reported 451 bioactive metabolites isolated from various groups of endophytic fungi from January 2015 to April 2021 along with their antibacterial profiling, chemical structures and mode of action. In addition, we also discussed various methods including epigenetic modifications, co-culture, and OSMAC to induce silent gene clusters for the production of noble bioactive compounds in endophytic fungi.

Synthetic and Naturally Occurring Heterocyclic Anticancer Compounds with Multiple Biological Targets

Cancer is a complex group of diseases initiated by abnormal cell division with the potential of spreading to other parts of the body. The advancement in the discoveries of omics and bio- and cheminformatics has led to the identification of drugs inhibiting putative targets including vascular endothelial growth factor (VEGF) family receptors, fibroblast growth factors (FGF), platelet derived growth factors (PDGF), epidermal growth factor (EGF), thymidine phosphorylase (TP), and neuropeptide Y4 (NY4), amongst others. Drug resistance, systemic toxicity, and drug ineffectiveness for various cancer chemo-treatments are widespread. Due to this, efficient therapeutic agents targeting two or more of the putative targets in different cancer cells are proposed as cutting edge treatments. Heterocyclic compounds, both synthetic and natural products, have, however, contributed immensely to chemotherapeutics for treatments of various diseases, but little is known about such compounds and their multimodal anticancer properties. A compendium of heterocyclic synthetic and natural product multitarget anticancer compounds, their IC50, and biological targets of inhibition are therefore presented in this review.

Evolutionary genomics and biosynthetic potential of novel environmental Actinobacteria

Actinobacteria embroil Gram-positive microbes with high guanine and cytosine contents in their DNA. They are the source of most antimicrobials of bacterial origin utilized in medicine today. Their genomes are among the richest in novel secondary metabolites with high biotechnological potential. Actinobacteria reveal complex patterns of evolution, responses, and adaptations to their environment, which are not yet well understood. We analyzed three novel plant isolates and explored their habitat adaptation, evolutionary patterns, and potential secondary metabolite production. The phylogenomically characterized isolates belonged to Actinoplanes sp. TFC3, Streptomyces sp. L06, and Embleya sp. NF3. Positively selected genes, relevant in strain evolution, encoded enzymes for stress resistance in all strains, including porphyrin, chlorophyll, and ubiquinone biosynthesis in Embleya sp. NF3. Streptomyces sp. L06 encoded for pantothenate and proteins for CoA biosynthesis with evidence of positive selection; furthermore, Actinoplanes sp. TFC3 encoded for a c-di-GMP synthetase, with adaptive mutations. Notably, the genomes harbored many genes involved in the biosynthesis of at least ten novel secondary metabolites, with many avenues for future new bioactive compound characterization-specifically, Streptomyces sp. L06 could make new ribosomally synthesized and post-translationally modified peptides, while Embleya sp. NF3 could produce new non-ribosomal peptide synthetases and ribosomally synthesized and post-translationally modified peptides. At the same time, TFC3 has particularly enriched in terpene and polyketide synthases. All the strains harbored conserved genes in response to diverse environmental stresses, plant growth promotion factors, and degradation of various carbohydrates, which supported their endophytic lifestyle and showed their capacity to colonize other niches. This study aims to provide a comprehensive estimation of the genomic features of novel Actinobacteria. It sets the groundwork for future research into experimental tests with new bioactive metabolites with potential application in medicine, biofertilizers, and plant biomass residue utilization, with potential application in medicine, as biofertilizers and in plant biomass residues utilization. KEY POINTS: • Potential of novel environmental bacteria for secondary metabolites production • Exploring the genomes of three novel endophytes isolated from a medicinal tree • Pan-genome analysis of Actinobacteria genera.

Fungal Depsides-Naturally Inspiring Molecules: Biosynthesis, Structural Characterization, and Biological Activities

Fungi represent a huge reservoir of structurally diverse bio-metabolites. Although there has been a marked increase in the number of isolated fungal metabolites over the past years, many hidden metabolites still need to be discovered. Depsides are a group of polyketides consisting of two or more ester-linked hydroxybenzoic acid moieties. They possess valuable bioactive properties, such as anticancer, antidiabetic, antibacterial, antiviral, anti-inflammatory, antifungal, antifouling, and antioxidant qualities, as well as various human enzyme-inhibitory activities. This review provides an overview of the reported data on fungal depsides, including their sources, biosynthesis, physical and spectral data, and bioactivities in the period from 1975 to 2020. Overall, 110 metabolites and more than 122 references are confirmed. This is the first review of these multi-faceted metabolites from fungi.

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.

Further Biochemical Profiling of Hypholoma fasciculare Metabolome Reveals Its Chemogenetic Diversity

Natural products with novel chemistry are urgently needed to battle the continued increase in microbial drug resistance. Mushroom-forming fungi are underutilized as a source of novel antibiotics in the literature due to their challenging culture preparation and genetic intractability. However, modern fungal molecular and synthetic biology tools have renewed interest in exploring mushroom fungi for novel therapeutic agents. The aims of this study were to investigate the secondary metabolites of nine basidiomycetes, screen their biological and chemical properties, and then investigate the genetic pathways associated with their production. Of the nine fungi selected, Hypholoma fasciculare was revealed to be a highly active antagonistic species, with antimicrobial activity against three different microorganisms: Bacillus subtilis, Escherichia coli, and Saccharomyces cerevisiae. Genomic comparisons and chromatographic studies were employed to characterize more than 15 biosynthetic gene clusters and resulted in the identification of 3,5-dichloromethoxy benzoic acid as a potential antibacterial compound. The biosynthetic gene cluster for this product is also predicted. This study reinforces the potential of mushroom-forming fungi as an underexplored reservoir of bioactive natural products. Access to genomic data, and chemical-based frameworks, will assist the development and application of novel molecules with applications in both the pharmaceutical and agrochemical industries.

Effect of Non-natural Hydrophobic Amino Acids on the Efficacy and Properties of the Antimicrobial Peptide C18G

Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules through evolution. The peptides are known to selectively bind to bacterial cell surfaces through electrostatic interactions, and subsequently, the peptides insert into the cell membrane and cause local disruptions of membrane integrity leading to cell death. Previous experiments showed that replacing the Leu residues in the AMP C18G with other naturally occurring hydrophobic residues resulted in side-chain-dependent activities. This work extends the investigation to non-natural hydrophobic amino acids and the effect on peptide activity. Minimal inhibitory concentration (MIC) results demonstrated that amino acid substitutions containing long flexible carbon chains maintained or increased antimicrobial activity compared to natural analogues. In solution, the peptide showed aggregation only with the most hydrophobic non-natural amino acid substitutions. Binding assays using Trp fluorescence confirm a binding preference for anionic lipids while quenching experiments demonstrated that the more hydrophobic peptides are more deeply buried in the anionic lipid bilayers compared to the zwitterionic bilayers. The most effective peptides at killing bacteria were also those which showed some level of disruption of bacterial membranes; however, one peptide sequence exhibited very strong activity and very low levels of red blood cell hemolysis, yielding a promising target for future development.

Risk of wild fungi treatment failure: Phallus impudicus-induced telomere damage triggers p21/p53 and p16-dependent cell cycle arrest and may contribute to male fertility reduction in vitro

The multifunctional characteristics of Phallus impudicus extract encourage to conduct research for its potential use in medical applications. Well, science is constantly seeking new evidence for the biological activity of extracts of natural origin. Drugs of natural origin should not cause any side effects on the physiological functions of the human body; however, this is not always successful. In this study, we used in vitro approach to evaluate the toxicity of alcohol Phallus impudicus extract on spermatogenic cells. We show, for the first time, cytotoxic properties of Phallus impudicus treatment associated with a decrease in cellular metabolic activity, dysregulation of redox homeostasis and impairment of selected antioxidant cell protection systems. As a consequence, p53/p21- and p16-mediated cell cycle arrest followed by p27 activation is initiated. The observed changes were associated with telomere shortening and numerous DNA damage at the chromosome ends (altered expression pattern of TRF1 and TRF2 proteins), as well as upregulation of cleaved caspase-3 with a decrease in Bcl-2 expression, suggesting induction of apoptotic death. Therefore, these results provide molecular evidence for mechanistic pathways and novel adverse outcomes linked to the Phallus impudicus treatment towards men's health and fertility reduction.

Metabolites from Wild Potato Inhibit Virulence Factors of the Soft Rot and Blackleg Pathogen Pectobacterium brasiliense

Potato (Solanum tuberosum L.) is the primary vegetable crop consumed worldwide and is largely affected by bacterial pathogens that can cause soft rot and blackleg disease. Recently, resistance to these diseases has been identified in the wild potato S. chacoense, and the mechanism of resistance is unknown. Here, it was hypothesized that S. chacoense stems or tubers have unique chemistry that confers resistance to the pathogen Pectobacterium brasiliense through bactericidal, bacteriostatic, or antivirulence activity. Stem and tuber metabolite extracts were collected from S. chacoense and tested for effects on Pectobacterium bacterial multiplication rates, and activity and expression of known exoenzymes and virulence genes using S. tuberosum extracts as a comparative control. Comparatively, the S. chacoense extracts did not affect bacterial multiplication rate; however, they did reduce pectinase, cellulase, and protease activities. The chemical extracts were profiled using a bioassay-guided fractionation, and a nontargeted metabolomics comparison of S. chacoense and S. tuberosum stems and tubers was performed. The data showed that selected alkaloids, phenolic amines, phenols, amines, and peptides are integrative chemical sources of resistance against the bacteria.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Endophytic Fungi: From Symbiosis to Secondary Metabolite Communications or Vice Versa?

Endophytic fungi (EF) are a group of fascinating host-associated fungal communities that colonize the intercellular or intracellular spaces of host tissues, providing beneficial effects to their hosts while gaining advantages. In recent decades, accumulated research on endophytic fungi has revealed their biodiversity, wide-ranging ecological distribution, and multidimensional interactions with host plants and other microbiomes in the symbiotic continuum. In this review, we highlight the role of secondary metabolites (SMs) as effectors in these multidimensional interactions, and the biosynthesis of SMs in symbiosis via complex gene expression regulation mechanisms in the symbiotic continuum and via the mimicry or alteration of phytochemical production in host plants. Alternative biological applications of SMs in modern medicine, agriculture, and industry and their major classes are also discussed. This review recapitulates an introduction to the research background, progress, and prospects of endophytic biology, and discusses problems and substantive challenges that need further study.

Natural Ergot Alkaloids in Ocular Pharmacotherapy: Known Molecules for Novel Nanoparticle-Based Delivery Systems

Several pharmacological properties are attributed to ergot alkaloids as a result of their antibacterial, antiproliferative, and antioxidant effects. Although known for their biomedical applications (e.g., for the treatment of glaucoma), most ergot alkaloids exhibit high toxicological risk and may even be lethal to humans and animals. Their pharmacological profile results from the structural similarity between lysergic acid-derived compounds and noradrenalin, dopamine, and serotonin neurotransmitters. To reduce their toxicological risk, while increasing their bioavailability, improved delivery systems were proposed. This review discusses the safety aspects of using ergot alkaloids in ocular pharmacology and proposes the development of lipid and polymeric nanoparticles for the topical administration of these drugs to enhance their therapeutic efficacy for the treatment of glaucoma.

Novel Antimicrobial Compounds as Ophiobolin-Type Sesterterpenes and Pimarane-Type Diterpene From Bipolaris Species TJ403-B1

Six previously undescribed ophiobolin-type sesterterpenes, namely, bipolatoxins A–F (1–6); and one previously undescribed pimarane-type diterpene, namely, 1β-hydroxy momilactone A (7); together with three known compounds, namely, 25-hydroxyophiobolin I (8), ophiobolin I (9), and ophiobolin A lactone (10); were isolated and identified from the endophytic fungus Bipolaris species TJ403-B1. Their structures with absolute configurations were elucidated on the basis of extensive spectroscopic analyses (including 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy data), single-crystal X-ray diffraction analyses, and comparison of experimental circular dichroism data. All compounds (except for 5) were evaluated for antimicrobial potential, which indicated that bipolatoxin D (4) showed significant inhibitory activity against Enterococcus faecalis with a minimum inhibitory concentration (MIC) value of 8 μg/mL, and ophiobolin A lactone (10) showed significant inhibitory activity against Acinetobacter baumannii and E. faecalis with MIC values of 8 and 8 μg/mL, respectively.