Antifeedant, Antifungal Cryptic Polyketides with Six Structural Frameworks from Tea Endophyte Daldinia eschscholtzii Propelled by the Antagonistic Coculture with Phytopathogen Colletotrichum pseudomajus and Different Culture Methods

The antagonistic coculture with tea phytopathogen Colletotrichum pseudomajus induces antifungal cryptic metabolites from isogenesis endophyte Daldinia eschscholtzii against tea phytopathogens. Sixteen new polyketides with six structural frameworks including ten cryptic ones, named coldaldols A-C (1-3), collediol (5), and daldinrins A-L (10-20 and 23), were found from the coculture of C. pseudomajus and D. eschscholtzii by different culture methods. The unique framework of compounds 11 and 12 featured a benzopyran-C7 polyketone hybrid, and compounds 13-16 were characterized by the novel benzopyran dimer. The structures were determined mainly by spectroscopic methods, including extensive one-dimensional (1D), two-dimensional (2D) NMR, high resolution electrospray ionisation mass spectroscopy (HRESIMS), ECD calculation, and single-crystal X-ray diffraction. The configuration of acyclic compounds 5 and 18 were determined by application of the universal NMR database. Most compounds showed significant antifungal activities against the tea pathogens C. pseudomajus and Alternaria sp. with MICs of 1-8 μg/mL. Compound 12 had stronger antifungal activity than that of positive drug nystatin. The ether bond at C-4 of the benzopyran derivative increased the antifungal activity. Compounds 4-9 and 11-23 showed antifeedant activities against silkworms with feeding deterrence indices of 15-100% at the concentration of 50 μg/cm2.

Diversified Polyketides With Anti-inflammatory Activities From Mangrove Endophytic Fungus Daldinia eschscholtzii KBJYZ-1

In total, five new polyketide derivatives: eschscholin B (2), dalditone A and B (3 and 4), (1R, 4R)-5-methoxy-1,2,3,4-tetrahydronaphthalene-1,4-dio (5), and daldilene A (6), together with 10 known as analogs (1, 7-15) were isolated from the mangrove endophytic fungus Daldinia eschscholtzii KBJYZ-1. Their structures and absolute configurations were established by extensive analysis of NMR and HRESIMS spectra data combined with ECD calculations and the reported literature. Compounds 2 and 6 showed significant cell-based anti-inflammatory activities with IC₅₀ values of 19.3 and 12.9 μM, respectively. In addition, western blot results suggested that compound 2 effectively inhibits the expression of iNOS and COX-2 in LPS-induced RAW264.7 cells. Further molecular biology work revealed the potential mechanism of 2 exerts anti-inflammatory function by inactivating the MAPK and NF-κB signaling pathways.

Mitochondrial damage produced by phytotoxic chromenone and chromanone derivatives from endophytic fungus Daldinia eschscholtzii strain GsE13

Bioassay-guided fractionation of the organic extracts of the endophyte Daldinia eschscholtzii strain GsE13 led to the isolation of several phytotoxic compounds, including two chromenone and two chromanone derivatives: 5-hydroxy-8-methoxy-2-methyl-4H-chromen-4-one, 1; 5-hydroxy-2-methyl-4H-chromen-4-one, 2; 5-methoxy-2-methyl-chroman-4-one, 3; and 5-methoxy-2-methyl-chroman-4-ol, 4; as well as other aromatic compounds: 4,8-dihydroxy-1-tetralone, 5; 1,8-dimethoxynaphthalene, 6; and 4,9-dihydroxy-1,2,11,12-tetrahydroperyl-ene-3,10-quinone, 7. Compounds 1, 4, and 7 were isolated for the first time from D. eschscholtzii. The phytotoxicity of all the compounds was determined on germination, root growth, and oxygen uptake in seedlings of a monocotyledonous (Panicum miliaceum) and three dicotyledonous plants (Medicago sativa, Trifolium pratense, and Amaranthus hypochondriacus). In general, root growth was the most affected process in all four weeds, and chromenones 1 and 2 were the most phytotoxic compounds. Phytotoxins 1-4 inhibited basal oxygen consumption rate in isolated mitochondria from M. sativa seedlings and also caused serious damage to their membrane potential (ΔΨm) in percentages greater than 50% at concentrations lower than 2 mM. Based on these results, compounds 1-4 of endophytic origin could be promising for the development of new herbicides potentially useful in agriculture or for the synthesis of promising new molecules. KEY POINTS: • Endophytic fungus Daldinia eschscholtzii produces phytotoxic compounds. • Phytotoxins inhibit basal oxygen consumption rate in isolated M. sativa mitochondria. • Phytotoxins altered the mitochondrial membrane potential.

Bioactive Secondary Metabolites from the Culture of the Mangrove-Derived Fungus Daldinia eschscholtzii HJ004

Two new polyketides, 8-O-methylnodulisporin F (1) and nodulisporin H (2), two new naphthoquinones, 5-hydroxy-2-methoxy-6,7-dimethyl-1,4-naphthoquinone (3) and 5-hydroxy-2-methoxynaphtho[9–c]furan-1,4-dione (4), and a new naphthofuran 1,3,8-trimethoxynaphtho[9–c]furan (5), along with five known compounds 4-O-methyl eleutherol (6), 2-acetyl-7-methoxybenzofuran (7), (-)-orthosporin (8), diaporthin (9), and 6-hydroxymellein (10), were obtained from the EtOAc extract of the mangrove-derived fungus Daldinia eschscholtzii HJ004. The structures of the isolated compounds were elucidated by extensive NMR and MS analyses, while the absolute configurations of the stereogenic carbons were established based on experimental and calculated electronic circular dichroism spectra. Compounds 4 and 7 displayed a potent inhibitory activity against α-glucosidase with the IC₅₀ values of 5.7 and 1.1 μg/mL, respectively. Compounds 1 and 2 showed a moderate antibacterial activity against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA) and Bacillus cereus, with minimum inhibitory concentration (MIC) values ranging from 6.25 to 12.5 μg/mL. Compound 3 exhibited antibacterial activity against B. cereus with the MIC value of 12.5 μg/mL.

A new chromone and a new aliphatic ester isolated from Daldinia eschscholtzii

A new chromone and a new aliphatic ester were isolated from the EtOAc extract of myceliums of Daldinia eschscholtzii. Their structures were elucidated as (R)-5-hydroxy-8-methoxy-2-methylchroman-4-one (1) and (E)-6-(non-3-en-1-yl) -2H-pyran-2-one (2) by interpretation of the spectroscopic evidence.

One new cytochalasin metabolite isolated from a mangrove-derived fungus Daldinia eschscholtzii HJ001

One new cytochalasin metabolite [11]-cytochalasa-5(6),13-diene-1,21-dione-7,18-dihydroxy-16,18-dimethyl-10-phenyl-(7S*,13E,16S*,18R*) (1), together with three known compounds (2-4) were obtained from the EtOAc extract of the endophytic fungus Daldinia eschscholtzii HJ001 isolated from the mangrove Brguiera sexangula var. rhynchopetala collected in the South China Sea. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. Compounds 1 and 2 were evaluated for their antibacterial and cytotoxic activities.

Identification and characterization of Daldinia eschscholtzii isolated from skin scrapings, nails, and blood

BACKGROUND

Daldinia eschscholtzii is a filamentous wood-inhabiting endophyte commonly found in woody plants. Here, we report the identification and characterization of nine D. eschscholtzii isolates from skin scrapings, nail clippings, and blood.

METHODS

The nine isolates were identified based on colony morphology, light microscopy, and internal transcribed spacer (ITS)-based phylogeny. In vitro antifungal susceptibility of the fungal isolates was evaluated by the Etest to determine the minimum inhibitory concentration (MIC).

RESULTS

The nine isolates examined were confirmed as D. eschscholtzii. They exhibited typical features of Daldinia sp. on Sabouraud Dextrose Agar, with white felty colonies and black-gray coloration on the reverse side. Septate hyphae, branching conidiophore with conidiogenous cells budding from its terminus, and nodulisporium-like conidiophores were observed under the microscope. Phylogenetic analysis revealed that the nine isolates were clustered within the D. eschscholtzii species complex. All the isolates exhibited low MICs against azole agents (voriconazole, posaconazole, itraconazole, and ketoconazole), as well as amphotericin B, with MIC of less than 1 µg/ml.

DISCUSSION

Early and definitive identification of D. eschscholtzii is vital to reducing misuse of antimicrobial agents. Detailed morphological and molecular characterization as well as antifungal profiling of D. eschscholtzii provide the basis for future studies on its biology, pathogenicity, and medicinal potential.

A new hydronaphthalenone from the mangrove-derived Daldinia eschscholtzii PSU-STD57

One new hydronaphthalenone derivative (1) was isolated from the broth extract of the endophytic fungus Daldinia eschscholtzii PSU-STD57 together with five known compounds, isosclerone (2), 8-methoxy-1-naphthol, 1,8-dimethoxynaphthalene, 2,6-dihydroxyphenyl-1-butan-1-one and tyrosol. The structures were assigned by spectroscopic methods. All the compounds were tested for antimicrobial activity against Staphylococcus aureus, methicillin-resistant S. aureus and Microsporum gypseum.