Identification and biological evaluation of secondary metabolites from the endolichenic fungus Aspergillus versicolor

New bisabolane-type sesquiterpenoid from Aspergillus sydowii BTBU20213012

A new bisabolane-type sesquiterpenoid, named (+)-8-dehydroxylaustrosene (1), along with ten known compounds, penicibisabolanes E (2) and G (3), (+)-austrosene (4), (S)-(+)-11-dehydrosydonic acid (5), sydonic acid (6), (7S,11S)-(+)-12-hydroxysydonic acid (7), (-)-(R)-hydroxysydonic acid (8), pseudaboydin A (9), (-)-(7 R,10R)-iso-10-hydroxysydowic acid (10), lumichrome (11), were identified from the fungus Aspergillus sydowii BTBU20213012 isolated from a marine sediment sample from the Western Pacific. The structures of the compounds were identified by HRESIMS and NMR data analysis. Compound 11 showed weak antimicrobial activity against Staphylococcus aureus with MIC value of 200 μg/mL.

Two new types of structures from soft coral-associated epiphytic fungus Aspergillus versicolor CGF9-1-2

Global Natural Products Social (GNPS) molecular networking platform was applied to discovery the undescribed compounds from the common marine fungi Aspergillus versicolor CGF9-1-2, ultimately resulting in isolation of four new polyketides, decumbenone E (1), decumbenone F (2), 2'-epi-8-O-methylnidurufin (6), (-)-phomoindene A (7), one new nucleoside, 3-methyl-9-(2-methylbutene)-xanthine (8), and five known analogues. Their structures were elucidated based on 1D/2D NMR spectroscopic and HRESIMS data analyses, meanwhile, the absolute configurations of new compounds were established based on the X-ray crystallographic experiments, as well as the electronic circular dichroism (ECD) analysis. All compounds were predicted pharmaceutical chemistry with ten commonly disease-related proteins by molecular docking. In addition, all compounds against TDP1 were performed in vitro, which was consistent with the docking result, and compound 6 shown a weak inhibitory activity.

In vitro Antibacterial Activity and Secondary Metabolite Profiling of Endolichenic Fungi Isolated from Genus Parmotrema

The endolichenic fungi are an unexplored group of organisms for the production of bioactive secondary metabolites. The aim of the present study is to determine the antibacterial potential of endolichenic fungi isolated from genus Parmotrema. The study is continuation of our previous work, wherein a total of 73 endolichenic fungi were isolated from the lichenized fungi, which resulted in 47 species under 23 genera. All the isolated endolichenic fungi were screened for preliminary antibacterial activity. Five endolichenic fungi-Daldinia eschscholtzii, Nemania diffusa, Preussia sp., Trichoderma sp. and Xylaria feejeensis, were selected for further antibacterial activity by disc diffusion method. The zone of inhibition ranged from 14.3 ± 0.1 to 23.2 ± 0.1. The chemical composition of the selected endolichenic fungi was analysed through GC-MS, which yielded a total of 108 compounds from all the selected five endolichenic fungi. Diethyl phthalate, 1-hexadecanol, dibutyl phthalate, n-tetracosanol-1, 1-nonadecene, pyrrol[1,2-a] pyrazine-1,4-dione, hexahydro-3-(2-methyl) and tetratetracontane were found to be common compounds among one or the other endolichenic fungi, which possibly were responsible for antibacterial activity. GC-MS data were further analysed through Principal Component Analysis which showed D. eschscholtzii to be with unique pattern of expression of metabolites. Compound confirmation test revealed coumaric acid to be responsible for antibacterial activity in D. eschscholtzii. So, the study proves that endolichenic fungi that inhabit lichenized fungal thalli could be a source of potential antibacterial compounds.

Dibenzofurans from nature: Biosynthesis, structural diversity, sources, and bioactivities

Dibenzofurans are a small class of natural products with versatile biological activities that used to be thought to come mainly from lichens and ascomycetes. In fact, they are also distributed widely in higher plants, especially in the families Rosaceae and Myrtaceae. Dibenzofurans and derivatives from lichens and ascomycetes have been well reviewed, but dibenzofurans from all biological sources in nature have not been reviewed. In this review, dibenzofurans from all natural sources have been comprehensively reviewed, and a total of 211 dibenzofurans isolated and identified from organisms between 1843 and March 2023 are categorized and discussed, including their biosynthesis, structural diversity, sources, and bioactivities.

Three new metabolites from the endophyte Fusarium proliferatum T2-10

One new cyclopeptide, cyclo-(L-Trp-L-Phe-L-Phe) (1), one new 2-pyridone derivative, fusarone A (3), and one new natural indole derivative, ethyl 3-indoleacetate (4), along with six known compounds were isolated from the endophytic fungus Fusarium proliferatum T2-10. The planar structures of three new compounds were identified by spectral methods including 1D and 2D NMR techniques, and the absolute configuration of compound 1 was elucidated by Marfey-MS method. In addition, all compounds were evaluated for their cytotoxic and antibacterial activities in vitro. Compound 2 showed remarkable cytotoxic activities against two human hepatoma cell lines SMMC7721 and HepG2 with IC50 values of 5.89 ± 0.74 and 6.16 ± 0.52 μM, and showed moderate antibacterial activities against Staphylococcus aureus and Enterococcus faecalis with MIC values of 7.81 and 15.62 μg/mL, respectively.

Structure Revisions of Phenolic Bisabolane Sesquiterpenes and a Ferroptosis Inhibitor from the Marine-Derived Fungus Aspergillus versicolor YPH93

Seven new phenolic bisabolane sesquiterpenoids (1-7), along with 10 biogenetically related analogues (8-17), were obtained from the deep-sea-derived fungus Aspergillus versicolor YPH93. The structures were elucidated based on extensive analyses of the spectroscopic data. Compounds 1-3 are the first examples of phenolic bisabolanes that contain two hydroxy groups attached to the pyran ring. The structures of sydowic acid derivatives (1-6 and 8-10) were carefully studied, leading to the structure revisions of six known analogues, including a revision of the absolute configuration for sydowic acid (10). All metabolites were evaluated for their effects on ferroptosis. Compound 7 exerted inhibition on erastin/RSL3-induced ferroptosis with EC50 values ranging from 2 to 4 μM, while it exhibited no effects on TNFα-induced necroptosis or H2O2-induced cell necrosis.

Ferroptosis Inhibitory Compounds from the Deep-Sea-Derived Fungus Penicillium sp. MCCC 3A00126

Two new xanthones (1 and 2) were isolated from the deep-sea-derived fungus Penicillium sp. MCCC 3A00126 along with 34 known compounds (3-36). The structures of the new compounds were established by spectroscopic data. The absolute configuration of 1 was validated by comparison of experimental and calculated ECD spectra. All isolated compounds were evaluated for cytotoxicity and ferroptosis inhibitory activities. Compounds 14 and 15 exerted potent cytotoxicity against CCRF-CEM cells, with IC₅₀ values of 5.5 and 3.5 μM, respectively, whereas 26, 28, 33, and 34 significantly inhibited RSL3-induced ferroptosis, with EC₅₀ values of 11.6, 7.2, 11.8, and 2.2 μM, respectively.

Sulfoxide-Containing Bisabolane Sesquiterpenoids with Antimicrobial and Nematicidal Activities from the Marine-Derived Fungus Aspergillus sydowii LW09

Phytopathogens, such as phytopathogenic bacteria, fungi, and nematodes, have caused great losses of crops every year, seriously threatening human health and agricultural production. Moreover, marine-derived fungi are abundant sources of structurally unique and bioactive secondary metabolites that could be potential candidates for anti-phytopathogenic drugs. One new sulfoxide-containing bisabolane sesquiterpenoid aspersydosulfoxide A (1) and nine known analogues (2–10) were isolated from the marine-derived A. sydowii LW09. The absolute configuration of the sulfur stereogenic center in 1 was determined by electronic circular dichroism (ECD) calculations. Compound 5 showed inhibition activity against Pseudomonas syringae, with a minimum inhibitory concentration (MIC) value of 32 μg/mL, whereas, compounds 2, 7, and 8 showed antibacterial activities toward Ralstonia solanacarum, with the same MIC value at 32 μg/mL. Meanwhile, compounds 3, 7, and 8 inhibited the fungal spore germination of Fusarium oxysporum, with the half maximal effective concentration (EC50) values of 54.55, 77.16, and 1.85 μg/mL, respectively, while compounds 2, 3, 7, and 8 inhibited the fungal spore germination of Alternaria alternata, which could be induced by vacuolization of germ tubes, with EC50 values of 34.04, 44.44, 26.02, and 46.15 μg/mL, respectively. In addition, compounds 3, 7, and 8 exhibited nematicidal activities against Meloidogyne incognita second-stage juveniles (J2s). In addition, compound 8 possessed the strongest nematicidal activity of nearly 80% mortality at 60 h with the half lethal concentration (LC50) values of 192.40 μg/mL. Furthermore, compounds 3, 7, and 8 could paralyze the nematodes and then impair their pathogenicity.

1'-O-methyl-averantin isolated from the endolichenic fungus Jackrogersella sp. EL001672 suppresses colorectal cancer stemness via sonic Hedgehog and Notch signaling

Endolichenic fungi are host organisms that live on lichens and produce a wide variety of secondary metabolites. Colorectal cancer stem cells are capable of self-renewal and differentiation into cancer cells, which makes cancers difficult to eradicate. New alternative therapeutics are needed to inhibit the growth of tumor stem cells. This study examined the ability of an extract of Jackrogersella sp. EL001672 (derived from the lichen Cetraria sp.) and the isolated compound 1'-O-methyl-averantin to inhibit development of cancer stemness. The endolichenic fungus Jackrogersella sp. EL001672 (KACC 83021BP), derived from Cetraria sp., was grown in culture medium. The culture broth was extracted with acetone to obtain a crude extract. Column chromatography and reverse-phase HPLC were used to isolate an active compound. The anticancer activity of the extract and the isolated compound was evaluated by qRT-PCR and western blotting, and in cell viability, spheroid formation, and reporter assays. The acetone extract of EL001672 did not affect cell viability. However, 1'-O-methyl-averantin showed cytotoxic effects against cancer cell lines at 50 μg/mL and 25 μg/mL. Both the crude extract and 1'-O-methyl-averantin suppressed spheroid formation in CRC cell lines, and downregulated expression of stemness markers ALDH1, CD44, CD133, Lgr-5, Msi-1, and EphB1. To further characterize the mechanism underlying anti-stemness activity, we examined sonic Hedgehog and Notch signaling. The results showed that the crude extract and the 1'-O-methyl-averantin inhibited Gli1, Gli2, SMO, Bmi-1, Notch-1, Hes-1, and the CSL complex. Consequently, an acetone extract and 1'-O-methyl-averantin isolated from EL001672 suppresses colorectal cancer stemness by regulating the sonic Hedgehog and Notch signaling pathways.

Microwave-Assisted Cu-Catalyzed Diaryletherification for Facile Synthesis of Bioactive Prenylated Diresorcinols

Prenylated diresorcinols exhibit various bioactivities, including cytotoxic, antibacterial, and antifungal activities. Therefore, establishing facile and efficient synthetic routes for prenylated diresorcinols facilitates their development as chemical probes or drugs with a novel mode of action. In this study, microwave-assisted copper catalysis was explored as a cost-effective and environmentally friendly method for the cross-coupling of sterically hindered ortho-prenylated phenols and aryl halides to produce bioactive prenylated diresorcinols, diorcinol I and leotiomycene B. Notable advantages of microwave-assisted catalysis include not only operational simplicity and rapid heating but also shorter reaction times and higher chemical yields. In addition, highly regioselective prenylation of phenol was achieved for the preparation of ortho-prenyl phenol via directed lithiation and subsequent alkylation. This study provides valuable insights for the preparation of other bioactive prenylated diresorcinols. Furthermore, considering that prenylated benzenoids are biosynthetic precursors of various polycyclic natural products, this synthetic route could be expanded to more complex bioactive compounds possessing diaryl ethers.

Thiazolo[5,4-b]pyridine Alkaloid and Seven ar-Bisabol Sesquiterpenes Produced by the Endophytic Fungus Penicillium janthinellum

We investigated the secondary metabolites present in Penicillium janthinellum MPT-25, an endophytic fungus isolated from Taxus wallichiana var. chinensis (Pilger) Florin. Chemical characterization of the solid cultured extract resulted in the isolation of 11 compounds, including eight previously undescribed metabolites: a thiazolo[5,4-b]pyridine alkaloid, janthinedine A (1), and seven ar-bisabol sesquiterpenes, janthinepenes A-G (2-8). Their structures were elucidated by a combination of extensive spectroscopic methods, including single-crystal X-ray diffraction and ECD spectra. The antimicrobial activities of these compounds were evaluated against seven agricultural pathogenic fungi and eight clinically drug-resistant bacteria.

Production of secondary metabolites in stirred tank bioreactor co-cultures of Streptomyces noursei and Aspergillus terreus

The focus of the study was to characterize the bioprocess kinetics and secondary metabolites production in the novel microbial co-cultivation system involving Streptomyces noursei ATCC 11455 (the producer of an antifungal substance known as nystatin) and Aspergillus terreus ATCC 20542 (the source of lovastatin, a cholesterol-lowering drug). The investigated “A. terreus vs. S. noursei” stirred tank bioreactor co-cultures allowed for the concurrent development and observable biosynthetic activity of both species. In total, the production profiles of 50 secondary metabolites were monitored over the course of the study. The co-cultures were found to be effective in terms of enhancing the biosynthesis of several metabolic products, including mevinolinic acid, an acidic form of lovastatin. This work provided a methodological example of assessing the activity of a given strain in the co-culture by using the substrates which can be metabolized exclusively by this strain. Since S. noursei was shown to be incapable of lactose utilization, the observed changes in lactose levels were attributed to A. terreus and thus confirmed its viability. The study was complemented with the comparative microscopic observations of filamentous morphologies exhibited in the co-cultures and corresponding monocultures.

An acetonic extract and secondary metabolites from the endolichenic fungus Nemania sp. EL006872 exhibit immune checkpoint inhibitory activity in lung cancer cell

Background: Endolichenic fungi (ELF), which live the inside the lichen thallus, contain many secondary metabolites that show various biological activities. Recent studies show that lichen and ELF secondary metabolites have antioxidant, antibacterial, antifungal, cytotoxic, and anticancer activities.

Purpose: Here, the effects of an ELF extract and its bioactive compounds were investigated on the H1975 cell line focusing on immune checkpoint marker inhibition.

Methods: An ELF was isolated from the host lichen Bryoria fuscescens (Gyelnik) Brodo and D. Hawksw and identified the species as Nemania sp. EL006872. The fungus was cultured on agar medium and acetonic extracts were obtained. Secondary metabolites radianspenes C and D, and dahliane D, were isolated from the crude extract. The biological effects of both the crude extract and the isolated secondary metabolites were evaluated in cell viability, qRT-PCR assays, flow cytometry analysis and western blotting.

Results: The cell viability assay revealed that extracts from Nemania sp. EL006872 and the isolated secondary compounds had low cytotoxicity. The crude extract, radianspenes C and D, and dahliane D, suppressed expression of mRNA encoding PD-L1 and aromatic hydrocarbon receptor (AhR), and surface expression of PD-L1 protein by cells exposed to benzo[a] pyrene. Radianspenes C and D, and dahliane D, reduced expression of AhR, PD-L1, ICOSL, and GITRL proteins by H1975 lung cancer cells, as well as exerting anti-proliferative effects.

Conclusion: Radianspenes C and D, and dahliane D, bioactive compounds isolated from Nemania sp. EL006872 ELF, have the potential for use as immunotherapy and immunoncology treatments.

Interactions of fungi with non-isothiocyanate products of the plant glucosinolate pathway: A review on product formation, antifungal activity, mode of action and biotransformation

The glucosinolate pathway, which is present in the order Brassicales, is one of the most researched defensive natural product biosynthesis pathways. Its core molecules, the glucosinolates are broken down upon pathogen challenge or tissue damage to yield an array of natural products that may help plants defend against the stressor. Though the most widely known glucosinolate decomposition products are the antimicrobial isothiocyanates, there is a wide range of other volatile and non-volatile natural products that arise from this biosynthetic pathway. This review summarizes our current knowledge on the interaction of these much less examined, non-isothiocyanate products with fungi. It deals with compounds including (1) glucosinolates and their biosynthesis precursors; (2) glucosinolate-derived nitriles (e.g. derivatives of 1H-indole-3-acetonitrile), thiocyanates, epithionitriles and oxazolidine-2-thiones; (3) putative isothiocyanate downstream products such as raphanusamic acid, 1H-indole-3-methanol (= indole-3-carbinol) and its oligomers, 1H-indol-3-ylmethanamine and ascorbigen; (4) 1H-indole-3-acetonitrile downstream products such as 1H-indole-3-carbaldehyde (indole-3-carboxaldehyde), 1H-indole-3-carboxylic acid and their derivatives; and (5) indole phytoalexins including brassinin, cyclobrassinin and brassilexin. Herein, a literature review on the following aspects is provided: their direct antifungal activity and the proposed mechanisms of antifungal action, increased biosynthesis after fungal challenge, as well as data on their biotransformation/detoxification by fungi, including but not limited to fungal myrosinase activity.

Bisabolane Sesquiterpenes with Anti-Inflammatory Activities from the Endophytic Fungus Penicillium citrinum DF47

Seven new bisabolane-type sesquiterpenes (1-7), namely penicibisabolanes A-G, together with eight known analogs (8-15) were obtained from the AcOEt extract of the millet fermentation broth of the endophytic fungus Penicillium citrinum DF47, which was isolated from the fresh root of Codonopsis pilosula (Franch.) Nannf. The gross structures of new metabolites were determined on the basis of the spectroscopic data (HR-ESI-MS, 1D and 2D NMR spectra), while their absolute configurations were resolved by comparison of the experimental and calculated ECD spectra, in association with specific rotation data. Compound 1 is a rare seco-trinor-bisabolane sesquiterpene found in nature, while 3 is the first example of phenolic bisabolanes bearing a methoxy group at C-1. All the isolates were evaluated their inhibitory effects against NO production in lipopolysaccharides (LPS) stimulated RAW264.7 cells. Among them, compounds 7 and 13 showed moderately anti-inflammatory effects with the inhibitory rate more than 50 % at the concentration of 20 μM.

Molecular Insight into Gene Response of Diorcinol- and Rubrolide-Treated Biofilms of the Emerging Pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a multidrug-resistant human opportunistic pathogen. S. maltophilia contributes to disease progression in cystic fibrosis patients and is found in wounds and infected tissues and on catheter surfaces. Due to its well-known multidrug resistance, it is difficult to treat S. maltophilia infections. Strain-specific susceptibility to antimicrobials has also been reported in several studies. Recently, three fungal diorcinols and 14 rubrolides were shown to reduce S. maltophilia K279a biofilm formation. Based on these initial findings, we were interested to extend this approach by testing a larger number of diorcinols and rubrolides and to understand the molecular mechanisms behind the observed antibiofilm effects. Of 52 tested compounds, 30 were able to significantly reduce the biofilm thickness by up to 85% ± 15% and had strong effects on mature biofilms. All compounds with antibiofilm activity also significantly affected the biofilm architecture. Additional RNA-sequencing data of diorcinol- and rubrolide-treated biofilm cells of two clinical isolates (454 and K279) identified a small set of shared genes that were affected by these potent antibiofilm compounds. Among these, genes for iron transport, general metabolism, and membrane biosynthesis were most strongly and differentially regulated. A further hierarchical clustering and detailed structural inspection of the diorcinols and rubrolides implied that a prenyl group as side chain of one of the phenyl groups of the diorcinols and an increasing degree of bromination of chlorinated rubrolides were possibly the cause of the strong antibiofilm effects. This study gives a deep insight into the effects of rubrolides and diorcinols on biofilms formed by the important global pathogen S. maltophilia.

IMPORTANCE Combating Stenotrophomonasmaltophilia biofilms in clinical and industrial settings has proven to be challenging. S. maltophilia is multidrug resistant, and occurrence of resistance to commonly used drugs as well as to antibiotic combinations, such as trimethoprim-sulfamethoxazole, is now frequently reported. It is therefore now necessary to look beyond conventional and already existing antimicrobial drugs when battling S. maltophilia biofilms. Our study contains comprehensive and detailed data sets for diorcinol and rubrolide-treated S. maltophilia biofilms. The study defines genes and pathways affected by treatment with these different compounds. These results, together with the identified structural elements that may be crucial for their antibiofilm activity, build a strong backbone for further research on diorcinols and rubrolides as novel and potent antibiofilm compounds.

Endolichenic Fungal Community Analysis by Pure Culture Isolation and Metabarcoding: A Case Study of Parmotrema tinctorum

Lichen is a symbiotic mutualism of mycobiont and photobiont that harbors diverse organisms including endolichenic fungi (ELF). Despite the taxonomic and ecological significance of ELF, no comparative investigation of an ELF community involving isolation of a pure culture and high-throughput sequencing has been conducted. Thus, we analyzed the ELF community in Parmotrema tinctorum by culture and metabarcoding. Alpha diversity of the ELF community was notably greater in metabarcoding than in culture-based analysis. Taxonomic proportions of the ELF community estimated by metabarcoding and by culture analyses showed remarkable differences: Sordariomycetes was the most dominant fungal class in culture-based analysis, while Dothideomycetes was the most abundant in metabarcoding analysis. Thirty-seven operational taxonomic units (OTUs) were commonly observed by culture- and metabarcoding-based analyses but relative abundances differed: most of common OTUs were underrepresented in metabarcoding. The ELF community differed in lichen segments and thalli in metabarcoding analysis. Dissimilarity of ELF community intra lichen thallus increased with thallus segment distance; inter-thallus ELF community dissimilarity was significantly greater than intra-thallus ELF community dissimilarity. Finally, we tested how many fungal sequence reads would be needed to ELF diversity with relationship assays between numbers of lichen segments and saturation patterns of OTU richness and sample coverage. At least 6000 sequence reads per lichen thallus were sufficient for prediction of overall ELF community diversity and 50,000 reads per thallus were enough to observe rare taxa of ELF.

Recent studies on terpenoids in Aspergillus fungi: Chemical diversity, biosynthesis, and bioactivity

Metabolites from fungi are a major source of natural small molecule drugs in addition to plants, while fungal derived terpenoids have been confirmed to have great potentials in many diseases. Aspergillus fungi are distributed in every corner of the earth, and their terpenoid metabolites exhibit promising diversity in term of both their chemistry and bioactivity. This review attempted to provide timely and comprehensive coverage of chemical, biosynthesis, and biological studies on terpenoids discovered from the genus Aspergillus, including mono-, sesqui-, di-, sester-, tri-, and meroterpenoids, in the last decade. The structural characteristics, biosynthesis, and pharmacological activities of 288 terpenoids were introduced.

Bisabolane-type sesquiterpenoids: Structural diversity and biological activity

Bisabolane-type sesquiterpenoids, a class of monocyclic sesquiterpenoids, are widely distributed in nature and have a variety of biological activities. To provide a reference for the further research and development of these compounds, the phytochemical and biological properties of natural bisabolane-type sesquiterpenoids (356 compounds in total) isolated between 1985 and 2020 from 24 families, primarily Compositae, Zingiberaceae, Aspergillaceae, Halichondriidae, and Aplysiidae were reviewed. In vitro and in vivo studies have indicated that antibacterial, anti-inflammatory, and cytotoxic effects are the most commonly reported pharmacological properties of bisabolane-type sesquiterpenoids. Owing to their extensive significant effects, a lot of traditional medicines containing this type of compounds have been used for a long history. Thus, bisabolane-type sesquiterpenoids are a rich source of important natural products, which show great potential for the development of new drugs.

Antifungal Activity of an Endophytic Fungus Aspergillus versicolor DYSJ3 from Aphanamixis grandifolia Blume against Colletotrichum musae

An endophytic fungus strain DYSJ3 was isolated from a stem of Aphanamixis grandifolia Blume, which was identified as Aspergillus versicolor based on the morphological characteristics, internal transcribed spacer (ITS) and calmodulin gene sequences analyses. A. versicolor DYSJ3 exhibited strong antagonistic activity against Colletotrichum musae, C. gloeosporioides and Fusarium oxysporum f. sp. cubense with the inhibition rates of 61.9, 51.2 and 55.3% respectively. The antifungal metabolites mainly existed in the mycelium of A. versicolor DYSJ3, and its mycelial crude extract (CE) had broad-spectrum antifungal activities against plant pathogenic fungi. The CE had a good thermal stability, and the inhibition rate of 100 µg/mL CE against C. musae was above 70.0% after disposing at 120 °C for 1 h. Five secondary metabolites were isolated from the CE and identified as averufanin, ergosterol peroxide, versicolorin B, averythrin and sterigmatocystin. Activity evaluation showed versicolorin B exhibited inhibitory effects on the mycelial growth and conidial germination of C. musae, and sterigmatocystin had a weak inhibitory effect on the mycelial growth of C. musae.

An Updated Review of Secondary Metabolites from Marine Fungi

Marine fungi are valuable and richest sources of novel natural products for medicinal and pharmaceutical industries. Nutrient depletion, competition or any other type of metabolic stress which limits marine fungal growth promotes the formation and secretion of secondary metabolites. Generally secondary metabolites can be produced by many different metabolic pathways and include antibiotics, cytotoxic and cyto-stimulatory compounds. Marine fungi produce many different types of secondary metabolites that are of commercial importance. This review paper deals with around 187 novel compounds and 212 other known compounds with anticancer and antibacterial activities with a special focus on the period from 2011-2019. Furthermore, this review highlights the sources of organisms, chemical classes and biological activities (anticancer and antibacterial) of metabolites, that were isolated and structurally elucidated from marine fungi to throw a helping hand for novel drug development.

Antimicrobial Compounds Isolated from Endolichenic Fungi: A Review

A lichen is a symbiotic relationship between a fungus and a photosynthetic organism, which is algae or cyanobacteria. Endolichenic fungi are a group of microfungi that resides asymptomatically within the thalli of lichens. Endolichenic fungi can be recognized as luxuriant metabolic artists that produce propitious bioactive secondary metabolites. More than any other time, there is a worldwide search for new antibiotics due to the alarming increase in microbial resistance against the currently available therapeutics. Even though a few antimicrobial compounds have been isolated from endolichenic fungi, most of them have moderate activities, implying the need for further structural optimizations. Recognizing this timely need and the significance of endolichenic fungi as a promising source of antimicrobial compounds, the activity, sources and the structures of 31 antibacterial compounds, 58 antifungal compounds, two antiviral compounds and one antiplasmodial (antimalarial) compound are summarized in this review. In addition, an overview of the common scaffolds and structural features leading to the corresponding antimicrobial properties is provided as an aid for future studies. The current challenges and major drawbacks of research related to endolichenic fungi and the remedies for them have been suggested.

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.

Specialized metabolites of the United States lichen Niebla homalea and their antiproliferative activities

Three undescribed stictanes, nieblastictanes A-C, two flavicanes, nieblaflavicanes A and B, together with three already reported stictanes, along with the known compounds (+)-usnic acid, sekikaic acid, divaricatic acid, and divaricatinic acid methyl ester were isolated from an ethyl acetate extract of the western North American lichen Niebla homalea. The structures of the new and known compounds were established by spectroscopic methods including nuclear magnetic resonance spectroscopy, mass spectrometry and electronic circular dichroism. Among the compounds isolated, usnic acid exhibited moderately potent antiproliferative activities against the A2780 ovarian (IC₅₀ 3.8 μM) and MCF-7 breast cancer (IC₅₀ 6.8 μM) cell lines. A plausible mode of formation of the chlorine-containing compound nieblastictane C is provided and the contribution of the isolated compounds to the chemotaxonomy of United States lichen species of the genus Niebla is also discussed.

Assigning the Origin of Microbial Natural Products by Chemical Space Map and Machine Learning

Microbial natural products (NPs) are an important source of drugs, however, their structural diversity remains poorly understood. Here we used our recently reported MinHashed Atom Pair fingerprint with diameter of four bonds (MAP4), a fingerprint suitable for molecules across very different sizes, to analyze the Natural Products Atlas (NPAtlas), a database of 25,523 NPs of bacterial or fungal origin. To visualize NPAtlas by MAP4 similarity, we used the dimensionality reduction method tree map (TMAP). The resulting interactive map organizes molecules by physico-chemical properties and compound families such as peptides and glycosides. Remarkably, the map separates bacterial and fungal NPs from one another, revealing that these two compound families are intrinsically different despite their related biosynthetic pathways. We used these differences to train a machine learning model capable of distinguishing between NPs of bacterial or fungal origin.

Total Synthesis of Anti-MRSA Active Diorcinols and Analogues

Diorcinols and related prenylated diaryl ethers were reported to exhibit activity against methicillin-resistant clinical isolates of Staphylococcus aureus (MRSA). Within these lines, we report the first total synthesis of diorcinol D, I, J, the proposed structure of verticilatin and recently isolated antibacterial diaryl ether by using an efficient and highly divergent synthetic strategy. These total syntheses furnish the diaryl ethers in only five to seven steps employing a Pd-catalyzed diaryl ether coupling as the key step. The total synthesis led to the structural revision of the natural product verticilatin, which has been isolated from a plant pathogenic fungus. Furthermore, these structures were tested in order to determine their antibacterial activities against different MRSA strains as well as further Gram-positive and -negative bacteria.

Classification of Aspergillus, Penicillium, Talaromyces and related genera (Eurotiales): An overview of families, genera, subgenera, sections, series and species

The Eurotiales is a relatively large order of Ascomycetes with members frequently having positive and negative impact on human activities. Species within this order gain attention from various research fields such as food, indoor and medical mycology and biotechnology. In this article we give an overview of families and genera present in the Eurotiales and introduce an updated subgeneric, sectional and series classification for Aspergillus and Penicillium. Finally, a comprehensive list of accepted species in the Eurotiales is given. The classification of the Eurotiales at family and genus level is traditionally based on phenotypic characters, and this classification has since been challenged using sequence-based approaches. Here, we re-evaluated the relationships between families and genera of the Eurotiales using a nine-gene sequence dataset. Based on this analysis, the new family Penicillaginaceae is introduced and four known families are accepted: Aspergillaceae, Elaphomycetaceae, Thermoascaceae and Trichocomaceae. The Eurotiales includes 28 genera: 15 genera are accommodated in the Aspergillaceae (Aspergillago, Aspergillus, Evansstolkia, Hamigera, Leiothecium, Monascus, Penicilliopsis, Penicillium, Phialomyces, Pseudohamigera, Pseudopenicillium, Sclerocleista, Warcupiella, Xerochrysium and Xeromyces), eight in the Trichocomaceae (Acidotalaromyces, Ascospirella, Dendrosphaera, Rasamsonia, Sagenomella, Talaromyces, Thermomyces, Trichocoma), two in the Thermoascaceae (Paecilomyces, Thermoascus) and one in the Penicillaginaceae (Penicillago). The classification of the Elaphomycetaceae was not part of this study, but according to literature two genera are present in this family (Elaphomyces and Pseudotulostoma). The use of an infrageneric classification system has a long tradition in Aspergillus and Penicillium. Most recent taxonomic studies focused on the sectional level, resulting in a well-established sectional classification in these genera. In contrast, a series classification in Aspergillus and Penicillium is often outdated or lacking, but is still relevant, e.g., the allocation of a species to a series can be highly predictive in what functional characters the species might have and might be useful when using a phenotype-based identification. The majority of the series in Aspergillus and Penicillium are invalidly described and here we introduce a new series classification. Using a phylogenetic approach, often supported by phenotypic, physiologic and/or extrolite data, Aspergillus is subdivided in six subgenera, 27 sections (five new) and 75 series (73 new, one new combination), and Penicillium in two subgenera, 32 sections (seven new) and 89 series (57 new, six new combinations). Correct identification of species belonging to the Eurotiales is difficult, but crucial, as the species name is the linking pin to information. Lists of accepted species are a helpful aid for researchers to obtain a correct identification using the current taxonomic schemes. In the most recent list from 2014, 339 Aspergillus, 354 Penicillium and 88 Talaromyces species were accepted. These numbers increased significantly, and the current list includes 446 Aspergillus (32 % increase), 483 Penicillium (36 % increase) and 171 Talaromyces (94 % increase) species, showing the large diversity and high interest in these genera. We expanded this list with all genera and species belonging to the Eurotiales (except those belonging to Elaphomycetaceae). The list includes 1 187 species, distributed over 27 genera, and contains MycoBank numbers, collection numbers of type and ex-type cultures, subgenus, section and series classification data, information on the mode of reproduction, and GenBank accession numbers of ITS, beta-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) gene sequences.

Antimicrobial Sesquiterpenoid Derivatives and Monoterpenoids from the Deep-Sea Sediment-Derived Fungus Aspergillus versicolor SD-330

Two new antimicrobial bisabolane-type sesquiterpenoid derivatives, ent-aspergoterpenin C (compound 1) and 7-O-methylhydroxysydonic acid (2), and two new butyrolactone-type monoterpenoids, pestalotiolactones C (3) and D (4), along with a known monoterpenoid pestalotiolactone A (5) and four known bisabolane sesquiterpenoids (6-9), were isolated and identified from the deep-sea sediment-derived fungus Aspergillus versicolor SD-330. The structures of these compounds were elucidated on the basis of spectroscopic analysis, and the absolute configurations of the new compounds 1-4 were determined by the combination of NOESY and TDDFT-ECD calculations and X-ray crystallographic analysis. Additionally, we first determined and reported the absolute configuration of the known monoterpenoid pestalotiolactone A (5) through the X-ray crystallographic experiment. All of these isolated compounds were evaluated for antimicrobial activities against human and aquatic pathogenic bacteria. Compounds 1, 2, 6 and 9 exhibited selective inhibitory activities against zoonotic pathogenic bacteria such as Escherichia coli, Edwardsiella tarda, Vibrio anguillarum and V. harveyi, with MIC values ranging from 1.0 to 8.0 μg/mL.

Extracts of Flavoparmelia sp. Inhibit Receptor Activator of Nuclear Factor-κB Ligand-Mediated Osteoclast Differentiation

Background

Osteoporosis is a geriatric disease with diminished bone density. The increase in the number of patients and medical expenses due to a global aging society are recognized as problems. Bone loss is the most common symptom of bone disease, not only osteoporosis but Paget's disease, rheumatoid arthritis, multiple myeloma, and other diseases. The main cause of this symptoms is excessive increase in the number and activity of osteoclasts. Osteoclasts are multinucleated giant cells that can resorb bone. They are differentiated and activation from monocytes/macrophages in the presence of macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand (RANKL).

Methods

The effect of extract of Flavoparmelia sp. (EFV), a genus of lichenized fungi within the Parmeliaceae, on the differentiation of bone marrow-derived macrophages (BMMs) into osteoclasts was examined by phenotype assay and the cell cytotoxicity was evaluated by cell counting kit-8. The osteoclast differentiation-related genes and proteins were investigated by real-time polymerase chain reaction and immunoblotting. The functional activity of osteoclast in response to EFV treatment was evaluated by an Osteo Assay plate.

Results

In this study, we found that EFV, a genus of lichenized fungi within the Parmeliaceae, inhibited osteoclast formation. And we investigated its inhibitory mechanism. EFV reduced RANKL-mediated osteoclast formation and activation by inhibiting expression of nuclear factor of activated T cells 1, a key factor of osteoclastogenesis.

Conclusions

Taken together, our results show that EFV is a promising candidate for health functional foods or therapeutic agents that can help treat bone diseases such as osteoporosis.

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.

Diphenyl Ethers from a Marine-Derived Aspergillus sydowii

Six new diphenyl ethers (1⁻6) along with eleven known analogs were isolated from the ethyl acetate extract of a marine-derived Aspergillus sydowii guided by LC-UV-MS. Their structures were unambiguously characterized by HRESIMS, NMR, as well as chemical derivatization. Compounds 1 and 2 are rare diphenyl ether glycosides containing d-ribose. The absolute configuration of the sugar moieties in compounds 1⁻3 was determined by a LC-MS method. All the compounds were evaluated for their cytotoxicities against eight cancer cell lines, including 4T1, U937, PC3, HL-60, HT-29, A549, NCI-H460, and K562, and compounds 1, 5, 6, and 8⁻11 were found to exhibit selective cytotoxicity against different cancer cell lines.

Effect of Usnic Acid on Osteoclastogenic Activity

Osteoclasts are the only cells that can resorb bone and they are produced from monocytes/macrophages in the presence of M-CSF and RANKL and are activated in vivo by an immune response. Usnic acid is a secondary metabolite of lichen and has a unique dibenzofuran skeleton. It has been used for years in cosmetics, fragrances, and traditional medicines. It has a wide range of bioactivities, including anti-inflammatory, anti-bacterial, anti-cancer, anti-viral, and so on. However, the anti-osteoclastogenic activity of usnic acid has not been reported yet. In this study, we investigated whether usnic acid could affect RANKL-mediated osteoclastogenesis. Usnic acid significantly inhibited RANKL-mediated osteoclast formation and function by reducing the transcriptional and translational expression of NFATc1, a master regulator of osteoclastogenesis. In addition, it prevented lipopolysaccharides (LPS)-induced bone erosion in mice. Taken together, our results suggest that usnic acid might be a potential candidate for the treatment of osteoporosis.

Aspergoterpenins A⁻D: Four New Antimicrobial Bisabolane Sesquiterpenoid Derivatives from an Endophytic Fungus Aspergillus versicolor

Aspergoterpenins A⁻D (1⁻4), four new bisabolane sesquiterpenoid derivatives, were obtained from the endophytic fungus, Aspergillus versicolor, together with eight known compounds (5⁻12), and their structures were elucidated by a comprehensive analysis of their NMR (Nuclear Magnetic Resonance), MS (Mass Spectrum) and CD (Circular Dichroism) spectra. Aspergoterpenin A (1) was the first example with a characteristic ketal bridged-ring part in the degraded natural bisabolane-type sesquiterpene structures. The compounds 1⁻12 displayed no significant activities against four cancer cell lines (A549, Caski, HepG2 and MCF-7). Further, the antimicrobial activities to Erwinia carotovora sub sp. Carotovora were evaluated, and the results showed that compounds 1⁻12 displayed antimicrobial activities with MIC values ranging from 15.2 to 85.2 μg/mL.

Secondary metabolism in the lichen symbiosis

Lichens, which are defined by a core symbiosis between a mycobiont (fungal partner) and a photobiont (photoautotrophic partner), are in fact complex assemblages of microorganisms that constitute a largely untapped source of bioactive secondary metabolites. Historically, compounds isolated from lichens have predominantly been those produced by the dominant fungal partner, and these continue to be of great interest for their unique chemistry and biotechnological potential. In recent years it has become apparent that many photobionts and lichen-associated bacteria also produce a range of potentially valuable molecules. There is evidence to suggest that the unique nature of the symbiosis has played a substantial role in shaping many aspects of lichen chemistry, for example driving bacteria to produce metabolites that do not bring them direct benefit but are useful to the lichen as a whole. This is most evident in studies of cyanobacterial photobionts, which produce compounds that differ from free living cyanobacteria and are unique to symbiotic organisms. The roles that these and other lichen-derived molecules may play in communication and maintaining the symbiosis are poorly understood at present. Nonetheless, advances in genomics, mass spectrometry and other analytical technologies are continuing to illuminate the wealth of biological and chemical diversity present within the lichen holobiome. Implementation of novel biodiscovery strategies such as metagenomic screening, coupled with synthetic biology approaches to reconstitute, re-engineer and heterologously express lichen-derived biosynthetic gene clusters in a cultivable host, offer a promising means for tapping into this hitherto inaccessible wealth of natural products.

Acetonic extracts of the endolichenic fungus EL002332 isolated from Endocarpon pusillum exhibits anticancer activity in human gastric cancer cells

BACKGROUND

Endolichenic fungi are microbes that inhabit the thalli of lichens and produce various unique chemicals that can be used for pharmaceutical purposes.

PURPOSE

This study screened a library of endolichenic fungal extracts to identify novel anticancer agents capable of suppressing the tumorigenicity of human cancer cells.

METHODS

Active compounds were isolated from extracts of endolichenic fungi by column chromatography and reverse-phase HPLC. The anticancer effects of the extracts on cell viability was assessed with the use of MTT assay, Western blotting, fluorescence labeling of apoptotic cell, and flow cytometric analysis; and cell motility with the use of migration, invasion and soft agar colony-formation assay in vitro; and on skin and intraperitoneal mouse xenograft tumors in vivo were investigated. The therapeutic effects of the extract alone or in combination with the conventional chemoreagent docetaxel were analyzed by sulforhodamine B assay.

RESULTS

Acetone extracts of EL002332, isolated from Endocarpon pusillum collected in the China desert in 2010, showed selective cytotoxicity against AGS human gastric cancer cells and CT26 mouse colon cancer cells. An active pure compound named myC was isolated from mycelium acetone extracts in a liquid culture system and showed more potent cytotoxicity than crude extracts in the AGS cell line. Especially, myC greatly increased the apoptotic cell population at the IC₅₀ concentration and activated apoptotic signaling by regulating Bcl2 family protein expression and caspase pathway activity. EL002332 crude extracts and myC decreased AGS cell motility at sub-lethal concentrations. In vivo skin and intraperitoneal xenograft tumor experiments showed that the size of tumors and the tumor score were significantly smaller in EL002332 crude extract-treated groups than in control groups. EL002332 crude extracts showed synergistic effects with docetaxel on the AGS and TMK1 cell lines.

CONCLUSION

The endolichenic fungus EL002332 has potential anticancer activity in gastric cancer and peritoneal carcinomatosis.

Aspernolides L and M, new butyrolactones from the endophytic fungus Aspergillus versicolor

During the systematic search of active compounds from endophytic fungi, two new butyrolactones, namely aspernolides L (2) and M (4), together with four known compounds: 1-O-acetylglycerol (1), butyrolactone I (3), butyrolactone VI (5), and (+) alantrypinone (6) were characterized from the EtOAc extract of the endophytic fungus Aspergillus versicolor isolated from the roots of Pulicaria crispa (Asteraceae). Extensive spectroscopic analysis, including 1D, 2D NMR, and HRESIMS, was used to elucidate their structures. Compounds 1, 5, and 6 are reported for the first time from this fungus.

Diphenyl ethers from a marine-derived isolate of Aspergillus sp. CUGB-F046

One new diphenyl ether, diorcinol K (1), along with three known compounds, diorcinols D (2), F (3) and I (4) were isolated from the fermentation media of a marine-derived fungus Aspergillus sp. CUGB-F046 which was isolated from a sediment sample collected from the Bohai Sea, China. Their structures were elucidated by detailed spectroscopic methods. Compounds 1, 2 and 4 displayed significant antibacterial activities against Staphylococcus aureus and methicillin-resistant S. aureus with MIC values of 3.125, 6.25 and 6.25 μg/mL, respectively.

Species diversity of Aspergillus section Versicolores in clinical samples and antifungal susceptibility

Aspergillus section Versicolores includes species of clinical relevance and many others that have been poorly studied but are occasionally found in clinical samples. The aim of this study was to investigate, using a multilocus phylogenetic approach, the spectrum of species of the section Versicolores and to determine their in vitro antifungal susceptibility. The study was based on a set of 77 clinical isolates from different USA medical centres, which had been previously identified as belonging to this section. The genetic markers used were internal transcribed spacer (ITS), β-tubulin (BenA), calmodulin (CaM), and RNA polymerase II second largest subunit (RPB2), and the drugs tested, following the CLSI guidelines, were amphotericin B (AMB), itraconazole, posaconazole, voriconazole, anidulafungin, caspofungin, micafungin, terbinafine (TBF), and flucytosine (5FC). The most frequent species were Aspergillus sydowii (26 %), Aspergillus creber (22 %), and Aspergillus amoenus (18.2 %), followed by Aspergillus protuberus (13 %), Aspergillus jensenii (10.4 %), and Aspergillus tabacinus (5.2 %); while Aspergillus cvjetkovicii, Aspergillus fructus, Aspergillus puulaauensis, and Aspergillus versicolor were represented by only one isolate each (1.3 %). This is the first time that A. jensenii and A. puulaauensis have been reported from clinical samples. Considering the high number of isolates identified as belonging to this fungal group in this study, its clinical relevance should not be overlooked. Aspergillus versicolor, traditionally considered one of the most common species in this section in a clinical setting, was only rarely recovered in our study. The in vitro antifungal results showed that echinocandins and TBF were the most potent drugs, the azoles showed variable results, AMB was poorly active, and 5FC was the less active.

Symbiosis-inspired approaches to antibiotic discovery

Covering: 2010 up to 2017Life on Earth is characterized by a remarkable abundance of symbiotic and highly refined relationships among life forms. Defined as any kind of close, long-term association between two organisms, symbioses can be mutualistic, commensalistic or parasitic. Historically speaking, selective pressures have shaped symbioses in which one organism (typically a bacterium or fungus) generates bioactive small molecules that impact the host (and possibly other symbionts); the symbiosis is driven fundamentally by the genetic machineries available to the small molecule producer. The human microbiome is now integral to the most recent chapter in animal-microbe symbiosis studies and plant-microbe symbioses have significantly advanced our understanding of natural products biosynthesis; this also is the case for studies of fungal-microbe symbioses. However, much less is known about microbe-microbe systems involving interspecies interactions. Microbe-derived small molecules (i.e. antibiotics and quorum sensing molecules, etc.) have been shown to regulate transcription in microbes within the same environmental niche, suggesting interspecies interactions whereas, intraspecies interactions, such as those that exploit autoinducing small molecules, also modulate gene expression based on environmental cues. We, and others, contend that symbioses provide almost unlimited opportunities for the discovery of new bioactive compounds whose activities and applications have been evolutionarily optimized. Particularly intriguing is the possibility that environmental effectors can guide laboratory expression of secondary metabolites from "orphan", or silent, biosynthetic gene clusters (BGCs). Notably, many of the studies summarized here result from advances in "omics" technologies and highlight how symbioses have given rise to new anti-bacterial and antifungal natural products now being discovered.

Polyketide-Terpene Hybrid Metabolites from an Endolichenic Fungus Pestalotiopsis sp

Five new polyketide-terpene hybrid metabolites (1–5) with highly functionalized groups, together with six known derivatives (6–11), were isolated from the endolichenic fungus Pestalotiopsis sp. Their structures were elucidated by extensive NMR experiments including ¹H, ¹³C, HMQC, COSY, and HMBC. The relative configurations of the new compounds were determined by analysis of coupling constants and ROESY correlations. The absolute configurations especially the secondary alcohol at C-15 in 1 and secondary alcohol at C-14 in 5 were established via the CD experiments of the in situ formed [Rh₂(OCOCF₃)₄] complex with the acetonide derivatives. These compounds were tested for their inhibition activity against six plant pathogens. Compounds 1 and 5 exhibited pronounced efficiency against Fusarium oxysporum, and compounds 5 and 6 potently inhibited Fusarium gramineum with MIC value of 8 µg/mL, which revealed the plausible ecological role of endolichenic fungus in providing chemical protection for its host lichen in the fungus-plant relationship. The biosynthetic pathway of compounds 1–11 was postulated for the first time, which paved the way for its further biosynthesis research.

Endolichenic Fungi: A Hidden Reservoir of Next Generation Biopharmaceuticals

Endolichenic fungi (ELF) offer an opportunity to discover emerging natural drugs. ELF are promising bioresources given their ability to produce bioactive metabolites that represent unique and diverse structural classes. Here, we assess the potential of recent technologies to provide insight into the chemical diversity of ELF for biopharmaceutical development.

p-Terphenyl Derivatives from the Endolichenic Fungus Floricola striata

Ten new p-terphenyl derivatives, floricolins A-J (1-10), together with six known compounds (11-16), were isolated from the extract of the endolichenic fungus Floricola striata. Chemical structures of these compounds were elucidated using spectroscopic data (HRESIMS and NMR). Among them, 9 and 10 were enantiomeric mixtures, and their configurations were established by single-crystal X-ray diffraction analysis using Cu Kα radiation. Evaluation of the isolated compounds against Candida albicans revealed that the most active compound, 3 (MIC 8 μg/mL), exerted fungicidal action by destruction of the cell membrane.

Heptaketides from an Endolichenic Fungus Biatriospora sp. and Their Antifungal Activity

Twelve new heptaketides, biatriosporins A-L (1-12), biatriosporin M (13) (a ramulosin derivative), and 19 known compounds (14-32) were isolated from the endolichenic fungus Biatriospora sp. (8331C). The structures of these compounds were determined by analyzing MS and NMR data. The absolute configurations of compounds 1, 2, 7, and 9 were determined by single-crystal X-ray diffraction analysis, whereas compound 10 was deduced with Mosher's method. Four of the compounds were active in an antifungal assay. The most potent compound, compound 4, also sensitized clinically derived azole-resistant Candida albicans strains to fluconazole (FLC). A mechanistic investigation revealed that 4 inhibited the function of efflux pumps and reduced the transcriptional expression of the efflux-pump-related genes CDR1 and CDR2.