Antimicrobial properties of unusual eremophilanes from the endophytic Diaporthe sp. BCC69512.

Six undescribed infrequent eremophilane derivatives including diaportheremopholins A - F and its previously undescribed side chain (E)-2-methyloct-2-enoic acid, together with three known compounds (testacein, xestodecalactones B and C), were isolated from the endophytic fungus Diaporthe sp. BCC69512. The chemical structures were determined based on NMR spectroscopic information in conjunction with the evidence from NOESY spectrum, Mosher's application, and chemical reactions for corroborating the absolute configurations. The isolated compounds were evaluated for biological properties such as antimalarial, anti-TB, anti-phytopathogenic fungal, antibacterial activities and for cytotoxicity against malignant (MCF-7 and NCI-H187) and non-malignant (Vero) cells. Diaportheremopholins B (2) and E (5) possessed broad antimicrobial activity against Mycobacterium tuberculosis, Bacillus cereus, Alternaria brassicicola and Colletotrichum acutatum with MICs in a range of 25.0-50.0 µg/mL. Testacein (7) exhibited strong anti-A. brassicicola and anti-C. acutatum activities with equal MIC values of 3.13 µg/mL. Moreover, diaportheremopholin F (6) and compound 8 displayed antitubercular activity with equal MIC values of 50.0 µg/mL. All tested compounds were non-cytotoxic against MCF-7, NCI-H187, and Vero cells, except those compounds 2 and 5-7 exhibited weak cytotoxicity against both malignant and non-malignant cells with IC50 values in a range of 15.5-115.5 µM.

A theoretical study on radical scavenging activity of phenolic derivatives naturally found within Alternaria alternata extract.

The increasing oxidative stress demands potential chemical compounds derived from natural resources with good antioxidant activity to overcome adverse health issues. In this context, we investigated the antioxidant properties of four dibenzopyrone phenolic compounds obtained from the endophytic fungus Alternaria alternata: altenusin, altenusin B, alterlactone, and dehydroaltenusin using DFT calculations. Our investigation focused on understanding the structure-antioxidant property relationship. It delved into probing the activity by modelling the antioxidant mechanisms. The computed transition states and thermochemical parameters, along with the structural attributes, indicate that altenusin B has good antioxidant efficacy among the four compounds, and it follows the HAT mechanism in an aqueous phase. Remarkably, our findings indicate that altenusin B exhibits potent HOO˙ radical scavenging properties, characterized by the computed high rate constant. The molecular docking studies of these compounds with the pro-oxidant enzyme xanthine oxidase (XO) gave insights into the binding modes of the compounds in the protein environment. Furthermore, molecular dynamics (MD) simulations were employed to study the interaction and stability of the compounds inside the XO enzyme. Our exploration sheds light on the radical scavenging potential of the -OH sites and the underlying antioxidant mechanisms that underpin the compounds' effective antioxidant potential.

Natural Occurrence of Alternaria Toxins in Citrus-Based Products Collected from China in 2021.

A total of 181 citrus-based products, including dried fruits, canned fruits, and fruit juices, collected from China and from abroad in 2021 were analyzed for the four Alternaria toxins (ALTs): alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), and tenuazonic acid (TeA) via ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS). Although the concentrations of the four ALTs varied by product and geographically, TeA was the predominant toxin followed by AOH, AME, and TEN. Products made in China showed higher levels of ALTs than those made abroad. Maximum levels of TeA, AOH, and AME in analyzed domestic samples were 4.9-fold, 1.3-fold, and 1.2-fold, respectively, higher than those in imported products. Furthermore, 83.4% (151/181) of the analyzed citrus-based products were contaminated with at least two or more ALTs. There were significant positive correlations between AOH and AME, AME and TeA, and TeA and TEN in all analyzed samples. More importantly, the solid and the condensed liquid products had higher concentrations of ALTs than the semi-solid product samples, as well as tangerines, pummelos, and grapefruits compared to the other kinds of citrus-based products. In conclusion, co-contamination with ALTs in commercially available Chinese citrus-based products was universal. Extensive and systematic surveillance of ALTs in citrus-based products, both domestic and imported, is required to obtain more scientific data for the determination of the maximum allowable concentrations of ALTs in China.

Metabolite Analysis of Alternaria Mycotoxins by LC-MS/MS and Multiple Tools.

Alternaria fungi are widely distributed plant pathogens that invade crop products, causing significant economic damage. In addition, toxic secondary metabolites produced by the fungi can also endanger consumers. Many of these secondary metabolites are chemically characterized as mycotoxins. In this study, Q Exactive Orbitrap mass spectrometry was used for the non-targeted analysis of the metabolome of seven Alternaria isolates cultured on Potato Carrot Agar (PCA), Potato Dextrose Agar (PDA) and Potato Sucrose Agar (PSA) medium. Due to the difficulty of detecting modified toxins, an analytical strategy with multiple visual analysis tools was also used to determine the presence of sulfate conjugated toxins, as well as to visualize the molecular network of Alternaria toxins. The results show that PSA medium exhibits more advantageous properties for the culture of Alternaria, with more toxigenic species and quantities and more obvious metabolic pathways. Based on high-resolution tandem mass spectrometry (MS/MS) data, the mycotoxins and their metabolites were mainly clustered into four groups: alternariol (AOH)/alternariol monomethyl ether (AME)/altenusin (ALU)/altenuene (ALT)/dehydroaltenusin (DHA)/Desmethyldehydroaltenusin (DMDA) families, Altertoxin-I (ATX-I) family, tentoxin (TEN) family and tenuazonic acid (TeA) family. Moreover, the PSA medium is more suitable for the accumulation of AOH, AME, ALU, ALT, DHA and DMDA, while the PDA medium is more suitable for the accumulation of ATX-I, TEN and TeA. This research may provide theoretical support for the metabolomics study of Alternaria.

Root uptake and metabolization of Alternaria toxins by winter wheat plants using a hydroponic system.

Fungi of the genus Alternaria are ubiquitous in the environment. Their mycotoxins can leach out of contaminated plants or crop debris into the soil entering the plant via the roots. We aim to evaluate the importance of this entry pathway and its contribution to the overall content of Alternaria toxins (ATs) in wheat plants to better understand the soil-plant-phytopathogen system. A hydroponic cultivation system was established and wheat plants were cultivated for up to two weeks under optimal climate conditions. One half of the plants was treated with a nutrient solution spiked with alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA), whereas the other half of the plants was cultivated without mycotoxins. Plants were harvested after 1 and 2 weeks and analyzed using a QuEChERS-based extraction and an in-house validated LC-MS/MS method for quantification of the ATs in roots, crowns, and leaves separately. ATs were taken up by the roots and transported throughout the plant up to the leaves after 1 as well as 2 weeks of cultivation with the roots showing the highest ATs levels followed by the crowns and the leaves. In addition, numerous AOH and AME conjugates like glucosides, malonyl glucosides, sulfates, and di/trihexosides were detected in different plant compartments and identified by high-resolution mass spectrometry. This is the first study demonstrating the uptake of ATs in vivo using a hydroponic system and whole wheat plants examining both the distribution of ATs within the plant compartments and the modification of ATs by the wheat plants.

Development of a Novel LC-MS/MS Multi-Method for the Determination of Regulated and Emerging Food Contaminants Including Tenuazonic Acid, a Chromatographically Challenging Alternaria Toxin.

The regulation of food contaminants in the European Union (EU) is comprehensive, and there are several compounds in the register or being added to the recommendation list. Recently, European standard methods for analysis have also been issued. The quick analysis of different groups of analytes in one sample requires a number of methods and the simultaneous use of various instruments. The aim of the present study was to develop a method that could analyze several groups of food contaminants: in this case, 266 pesticides, 12 mycotoxins, 14 alkaloid toxins, and 3 Alternaria toxins. The main advantage of the herein described approach over other methods is the simultaneous analysis of tenuazonic acid (TEA) and other relevant food contaminants. The developed method unites the newly published standard methods such as EN 15662:2018, EN 17194:2019, EN 17256:2019, EN 17425:2021, EN 17521:2021, which describes the analysis of both regulated and emerging contaminants. The developed method is based on a QuEChERS sample preparation, followed by LC-MS/MS analysis under alkaline mobile phase conditions. The pH of the aqueous eluent was set to 8.3, which resulted in baseline separation among ergot alkaloids and their corresponding epimers, a symmetric chromatographic peak shape for analyzing TEA and fit-for-purpose sensitivity for MS/MS detection in both positive and negative ionization modes. Those compounds, which possess the corresponding isotopically labeled internal standards (ISTD), allowed for direct quantification by the developed method and no further confirmation was necessary. This was proven by satisfactory analyses of a number of quality control (QC), proficiency test (PT), and validation samples.

Altersteroids A-D, 9,11-Secosteroid-Derived γ-Lactones from an Alternaria sp.

Altersteroids A-D (1-4), four new 9,11-secosteroid-derived γ-lactones, were isolated from cultures of the ascomycete fungus Alternaria sp. Their structures were elucidated primarily by NMR experiments. The absolute configuration of 1 was established by X-ray crystallographic analysis of its di-p-nitrobenzenesulfonate 1a using Cu Kα radiation, whereas those for 2-4 were assigned by quantum-chemical calculations. Compounds 1-4 incorporate a γ-lactone moiety fused to the steroid D ring at C-13/C-14. Compound 3 showed moderate cytotoxicity toward four tumor cell lines and induced an apoptotic process in A549 cells. Notably, compound 3 showed equipotent activity against the cisplatin-sensitive MB49 and -resistant MB49 CisR cells, with an IC50 value of 12.7 µM.

Degradation of Alternaria mycotoxins by UV-C irradiation: Effect of selected process and exposure to food components.

Alternariol (AOH) and alternariol monomethyl ether (AME) are two Alternaria mycotoxins with high occurrence rates in food systems. This study aimed to investigate the photodegradation of AOH and AME by ultraviolet-C (UV-C) irradiation. The effect of UV-C intensity, pH, treatment time, solvents and the exposure of food components were evaluated. After treated by UV-C irradiation at 3500 µW/cm2 for 90 min, AOH samples in methanol, aqueous solution and solid state were degraded by 89.1%, 72.9% and 53.2%, respectively, while the degradation percentages of AME were 86.6%, 50.1% and 11.1%, respectively. Increasing irradiation intensity and prolonging irradiation time could significantly facilitate the degradation of AOH and AME. An alkaline environment (pH = 11) was more conducive to the degradation of toxins. In addition, 2.5 mg mL-1 citric acid or malic acid increased the photodegradation of AOH and AME to 94.6% and 95.3%, 93.2% and 70.5%, respectively. However, protein, polyphenols and vitamin C exerted inhibitory effects on the degradation, while 10% glucose or sucrose reduced the photodegradation of AOH and AME to 65.9% and 40.3%. UV-C treatment could effectively reduce the content of AOH and AME, with the highest efficiency achieved in methanol and alkaline environment. By contrast, UV-C irradiation is more effective in degrading toxins in some liquid foods rich in organic acids but lacking in protein. The utilization of UV-C radiation appears to be a potentially useful approach for decreasing the underlying risk of Alternaria mycotoxin contamination in foods.

Alternarialone A, a new curvularin-type metabolite from the mangrove-derived fungus Alternaria longipes.

Alternarialone A (1), one new curvularin derivative, and two known compounds (2 and 3) were isolated from the crude extract of the mangrove-derived fungus Alternaria longipes. Their structures were elucidated by comprehensive spectroscopic analyses, including MS and NMR spectroscopic data. The absolute configuration of 1 was assigned by 13C NMR calculations and a comparison of electronic circular dichroism (ECD) spectra. All compounds were evaluated for their antibacterial activities against Helicobacter pylori. Compounds 2 and 3 showed antibacterial activities against H. pylori G27 with MIC values of 8 and 16 µg/ml, respectively, while compound 3 also displayed antibacterial activity against H. pylori BHKS159 with the MIC value of 16 µg/ml.

New Dibenzo-α-pyrone Derivatives with α-Glucosidase Inhibitory Activities from the Marine-Derived Fungus Alternaria alternata.

Three new dibenzo-α-pyrone derivatives, alternolides A-C (1-3), and seven known congeners (4-10) were isolated from the marine-derived fungus of Alternaria alternata LW37 assisted by the one strain-many compounds (OSMAC) strategy. The structures of 1-3 were established by extensive spectroscopic analyses, and their absolute configurations were determined by modified Snatzke's method and electronic circular dichroism (ECD) calculations. Compounds 6 and 7 showed good 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant scavenging activities with IC50 values of 83.94 ± 4.14 and 23.60 ± 1.23 µM, respectively. Additionally, 2, 3 and 7 exhibited inhibitory effects against α-glucosidase with IC50 values of 725.85 ± 4.75, 451.25 ± 6.95 and 6.27 ± 0.68 µM, respectively. The enzyme kinetics study indicated 2 and 3 were mixed-type inhibitors of α-glucosidase with Ki values of 347.0 and 108.5 µM, respectively. Furthermore, the interactions of 2, 3 and 7 with α-glucosidase were investigated by molecular docking.

Natural Occurrence of Alternaria Toxins in Agricultural Products and Processed Foods Marketed in South Korea by LC-MS/MS.

Alternaria mycotoxins including alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), altertoxin-I (ATX-I), tentoxin (TEN), and tenuazonic acid (TeA), are ubiquitous contaminants in agricultural products. A method for the simultaneous determination of these six toxins by ultrahigh performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) with solid phase extraction (SPE) was validated in rice, sesame, tomato, and apple juice matrices. The performance of the method was evaluated in terms of linearity (R2 > 0.999), the limit of detection (0.04-1.67 µg/kg), the limit of quantification (0.12-5.06 µg/kg), recovery (80.0-114.7%), and precision (<17.7%). The validated method was applied to monitor 152 marketed food samples in South Korea, as well as to investigate the co-occurrence and correlation between Alternaria toxins. The mean occurrence levels were 2.77 µg/kg for AOH, 4.36 µg/kg for AME, 0.14 µg/kg for ALT, 0.11 µg/kg for ATX-I, 0.43 µg/kg for TEN, and 104.56 µg/kg for TeA. Mean and extreme (95th percentile) daily dietary exposures of South Koreans to Alternaria toxins were estimated to be 22.93 ng/kg b.w./day and 86.07 ng/kg b.w./day, respectively.

The Potential of Alternaria Toxins Production by A. alternata in Processing Tomatoes.

As a filamentous and spoilage fungus, Alternaria spp. can not only infect processing tomatoes, but also produce a variety of mycotoxins which harm the health of human beings. To explore the production of Alternaria toxins in processing tomatoes during growth and storage, four main Alternaria toxins and four conjugated toxins were detected by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and ultra-performance liquid chromatography-ion mobility quadrupole time-of-flight mass spectrometry (UPLC-IMS QToF MS) in processing tomatoes on different days after being inoculated with A. alternata. The results show that the content of Alternaria toxins in an in vivo assay is higher than that under field conditions. Tenuazonic acid (TeA) is the predominant toxin detected in the field (205.86~41,389.19 µg/kg) and in vivo (7.64~526,986.37 µg/kg) experiments, and the second-most abundant toxin is alternariol (AOH). In addition, a small quantity of conjugated toxins, AOH-9-glucoside (AOH-9-Glc) and alternariol monomethyl ether-3-glucoside (AME-3-Glc), were screened in the in vivo experiment. This is the first time the potential of Alternaria toxins produced in tomatoes during the harvest period has been studied in order to provide data for the prevention and control of Alternaria toxins.

Anti-Epstein-Barr Viral Agents from the Medicinal Herb-Derived Fungus Alternaria alstroemeriae Km2286.

Chromatographic separation on the liquid-state fermented products produced by the fungal strain Alternaria alstroemeriae Km2286 isolated from the littoral medicinal herb Atriplex maximowicziana Makino resulted in the isolation of compounds 1-9. Structures were determined by spectroscopic analysis as four undescribed perylenequinones, altertromins A-D (1-4), along with altertoxin IV (5), altertoxin VIII (6), stemphyperylenol (7), tenuazonic acid (8), and allo-tenuazonic acid (9). Compounds 1-6 exhibited antiviral activities against Epstein-Barr virus (EBV) with EC50 values ranging from 0.17 ± 0.07 to 3.13 ± 0.31 µM and selectivity indices higher than 10. In an anti-neuroinflammatory assay, compounds 1-4, 6, and 7 showed inhibitory activity of nitric oxide production in lipopolysaccharide-induced microglial BV-2 cells, with IC50 values ranging from 0.33 ± 0.04 to 4.08 ± 0.53 µM without significant cytotoxicity. This is the first report to describe perylenequinone-type compounds with potent anti-EBV and anti-neuroinflammatory activities.

Removal of Alternaria mycotoxins exposed to different food components by cold plasma.

Alternariol (AOH) and alternariol monomethyl ether (AME), the two Alternaria mycotoxins with the highest outbreak rates in food systems, could be effectively reduced by cold plasma. This research evaluated the impact of food components on the plasma removal of AOH and AME. The results showed that 6% whey protein or ovalbumin almost completely inhibited the reduction of AOH or AME. Polyphenols inhibited the removal of AOH and AME by up to 90.8% and 83.4%, respectively. Organic acids and Vc reduced AME removal by up to 43.4% and 31.9%, respectively, but had little effect on AOH removal. Sugars and amino acids could decrease both toxin removal by less than 10%. Proteins exhibited the most inhibitory effect on plasma removal of AOH and AME, followed by polyphenols, while the effect of other components was relatively small. AOH and AME removal by cold plasma was highly related to H2O2 produced during plasma discharge.

Alternaria alternata Mycotoxins Activate the Aryl Hydrocarbon Receptor and Nrf2-ARE Pathway to Alter the Structure and Immune Response of Colon Epithelial Cells.

After ingestion of food commodities, the gastrointestinal tract (GIT) poses the first barrier against xenobiotics and pathogens. Therefore, it is regularly confronted with external stressors potentially affecting the inflammatory response and the epithelial barrier. Alternaria mycotoxins such as alternariol (AOH) and altertoxin II (ATX-II) are frequently occurring food and feed contaminants that are described for their immunomodulatory capacities. Hence, this study aimed at exploring the effect of AOH and ATX-II as single compounds or binary mixtures on the immune response and epithelial homeostasis in noncancerous colon epithelial cells HCEC-1CT. Both toxins suppressed mRNA levels of proinflammatory mediators interleukin-8 (IL-8), tumor necrosis factor α (TNF-α), and secretion of IL-8, as well as mRNA levels of the matrix metallopeptidase 2 (MMP-2). Binary combinations of AOH and ATX-II reduced the response of the single toxins. Additionally, AOH and ATX-II modified immunolocalization of transmembrane proteins such as integrin ß1, zona occludens 1 (ZO-1), claudin 4 (Cldn 4), and occludin (Ocln), which support colonic tissue homeostasis and intestinal barrier function. Moreover, the cellular distribution of ZO-1 was affected by ATX-II. Mechanistically, these effects could be traced back to the involvement of several transcription factors. AOH activated the nuclear translocation of the aryl hydrocarbon receptor (AhR) and the nuclear factor erythroid 2-related factor 2 (Nrf2), governing cell metabolic competence and structural integrity. This was accompanied by altered distribution of the NF-κB p65 protein, an important regulator of inflammatory response. ATX-II also induced AhR and Nrf2 translocation, albeit failing to substantiate the effect of AOH on the colonic epithelium. Hence, both toxins coherently repress the intestinal immune response on the cytokine transcriptional and protein levels. Furthermore, both mycotoxins affected the colonic epithelial integrity by altering the cell architecture.

Development of analytical methods to study the effect of malting on levels of free and modified forms of Alternaria mycotoxins in barley.

A liquid chromatography tandem mass spectrometry (LC-MS/MS) multi-mycotoxin method was developed for the analysis of the Alternaria toxins alternariol (AOH), alternariol monomethyl ether (AME), tentoxin (TEN), altertoxin I (ATX I), altertoxin II (ATX II), alterperylenol (ALTP), and altenuene (ALT), as well as the modified toxins AOH-3-glucoside (AOH-3-G), AOH-9-glucoside (AOH-9-G), AME-3-glucoside (AME-3-G), AOH-3-sulfate (AOH-3-S), and AME-3-sulfate (AME-3-S) in barley and malt. The toxin tenuazonic acid (TeA) was analyzed separately as it could not be included into the multi-mycotoxin method. Quantitation was conducted by using a combination of stable isotope dilution analysis (SIDA) for AOH, AME, and TeA, and matrix-matched calibration for all other toxins. Limits of detection were between 0.05 µg/kg (AME) and 2.45 µg/kg (ALT), whereas limits of quantitation ranged from 0.16 µg/kg (AME) to 8.75 µg/kg (ALT). Recoveries between 96 and 107% were obtained for the analytes when SIDA was applied, while recoveries between 84 and 112% were found for analytes quantified by matrix-matched calibration. The method was applied for the analysis of 50 barley samples and their respective malts from the harvest years 2016-2020 for their mycotoxin content, showing the overall potential of toxin formation during the malting process. The toxins ALTP and ATX I were mainly found in the malt samples, but not in barley.

Alternatones A and B, two polyketides possessing novel skeletons from entophyte Alternaria alternate L-10.

On our ongoing searching for bioactive natural products derived from entophytes, two polyketides possessing novel skeletons, alternatones A-B (1-2), were identified from the culture of Alternaria alternate L-10. Their structures were established by a combination of spectroscopic and single-crystal X-ray diffraction with Cu Ka radiation. Alternatone A (1) exhibited cytotoxic activity against human hepatoma carcinoma HepG-2 cell line. The putative biosynthetic pathways for compounds 1-2 were also proposed.

UPLC-Q-TOF-MS/MS analysis of the guaiane sesquiterpenoids oxytropiols A-J and detection of undescribed analogues from the locoweed endophytic fungus Alternaria oxytropis (Pleosporaceae).

INTRODUCTION: In addition to the mycotoxin swainsonine, the locoweed endophytic fungus Alternaria oxytropis (Pleosporaceae) also produces a series of rarely reported, highly oxygenated bicyclic guaiane sesquiterpenoids. Few investigations on the electrospray tandem mass fragmentation pattern of this sesquiterpenoid have been reported. OBJECTIVES: We aimed to analyze and detect new guaiane sesquiterpenoid analogues from crude extracts of the locoweed endophytic fungus A. oxytropis by UPLC-Q-TOF-MS/MS experiments. MATERIALS AND METHODS: Oxytropiols A-J (1-10) and the extract of the locoweed endophytic fungus A. oxytropis were analyzed by UPLC-Q-TOF-MS/MS in positive mode. RESULTS: Typical neutral losses, McLafferty rearrangement, 1,2-rearrangement, and 1,3-rearrangement were considered to be the main fragmentation patterns for the [M + H]+ /[M + Na]+ ions of 1-10 by UPLC-Q-TOF-MS/MS experiments, and possible fragmentation pathways of 1-10 were suggested. A unique and undescribed analogue named oxytropiol K (11) was found in the extract based on UPLC-Q-TOF-MS/MS analysis. Compound 11 was isolated and elucidated by NMR spectrometry, and its UPLC-Q-TOF-MS/MS analysis was consistent with the fragmentation pathways of 1-10. CONCLUSION: The results further support that UPLC-Q-TOF-MS/MS is a powerful and sensitive tool for the characterization of known compounds (dereplication) and the detection of new analogues from crude extracts and imply that the locoweed endophytic fungus A. oxytropis, with few chemical investigations, is an important resource for undescribed metabolites.

Identification and Toxicological Characterization of Alternaria japonica Strains.

Fungi of the genus Alternaria are producers of biologically active compounds. Alternaria japonica is pathogenic to small radish and certain other crucifers, but has not been studied in sufficient detail. Discrepant data on its toxic metabolites are available in the literature, possibly because a limited set of nutritive substrates was used in culturing or species identification of the strains was incorrect. The objectives of this study were to accurately identify the Russian A. japonica strains and to assess the A. japonica toxigenic potential. Four Russian A. japonica strains were identified using a multifaceted approach, which included analyses of morphological characters (the diameter and morphology of colonies grown on the diagnostic media potato carrot agar (PCA) and yeast extract-glucose (YES) agar for one week), the conidial size, and the presence of chlamydospores), the nucleotide sequences of DNA markers (ITS and EF1α regions), and chemotaxonomic data (mycotoxin production). Biomass and extractive substance yields of A. japonica cultures were found to significantly depend on the composition of the liquid medium. Minor differences between the A. japonica strains were detected via metabolite profiling by HPLC/MS-UV. Extracts of A. japonica cultures exerted phytotoxic activity toward small radish leaves and cytotoxicity toward Paramecium caudatum to a level comparable with that of A. tenuissima extracts. Brassicicolin A, dihydrobrassicicolin A, and phomenins A and B, which are known for several species of the genus Alternaria, were identified in A. japonica extracts. Mycotoxins (alternariol, its methyl ether, tentoxin, tenuazonic acid, and altenuene), which are characteristic of the cosmopolitan species A. tenuissima, were not detected in cultures of the A. japonica strains. Extract toxicity and the yield of extractive substances were studied in the A. japonica strains, and strain MFP244011 proved promising as a producer of known and, presumably, new toxins upon culture on the M1D synthetic medium or semisynthetic liquid media (e.g., the Sabouraud medium).

Antibacterial and antioxidant activities of endophytic fungi and nettle (Urtica dioica L.) leaves as their host.

Nettle (Urtica dioica L), as a plant rich in biologically active compounds, is one of the most important plants used in herbal medicine. Studies have shown that this plant has antioxidant, antiplatelet, hypoglycemic and hypocholesterolemia effects. In this study, we characterized three Alternaria endophytic fungi isolated from their host U. dioica. We hypothesized that these endophytic fungi can produce new bioactive metabolites, which may possess the bioactive property with potential application in the medical and pharmaceutical industries. The antibacterial activity was evaluated against reference and isolated strains, including Methicillin-Resistant Staphylococcus aureus. A wide range of antimicrobial activities similar to those measured in nettle leaves was detected especially for Alternaria sorghi. Furthermore, the highest antioxidant activity detected with DPPH free radical scavenging was measured for A. sorghi and nettle leaves ethyl acetate extracts. In addition, whereas catalase activity was similar in the three isolated fungi and nettle leaves, total thiol content and superoxide dismutase activity were significantly higher in leaves. A. sorghi showed the best activities compared to other isolated fungi. The characterization and further production of bioactive compounds produced by this endophyte should be investigated to fight bacteria and especially those that develop drug multi-resistance.