Triterpenes with unusual modifications from the fruiting bodies of the medicinal fungus Irpex lacteus

Two New Compounds from the Fungus Xylaria nigripes

In the process of discovering more neural-system-related bioactive compounds from Xylaria nigripes, xylariamino acid A (1), a new amino acid derivative, and a new isovaleric acid phenethyl ester (2) were isolated and identified. Their structures and absolute configurations were determined by analyses of IR, HRESIMS, NMR spectroscopic data, and gauge-independent atomic orbital (GIAO) NMR calculation, as well as electronic circular dichroism (ECD) calculation. The isolated compounds were evaluated for their neuroprotective effects against damage to PC12 cells by oxygen and glucose deprivation (OGD). Compounds 1 and 2 can increase the viability of OGD-induced PC12 cells at all tested concentrations. Moreover, compound 2 (1 μmol L^-1) can significantly reduce the percentage of apoptotic cells.

Ganoaustralins A and B, Unusual Aromatic Triterpenes from the Mushroom Ganoderma australe

Two triterpenes, ganoaustralins A (1) and B (2), featuring unprecedented 6/6/6/5/6 scaffolds were isolated from the fruiting bodies of the mushroom Ganoderma australe. The structures were determined by extensive NMR and HRESIMS spectroscopic analysis. The absolute configuration of the C-25 in ganoaustralin A was assigned by the phenylglycine methyl ester (PGME) method. The relative and absolute configurations of the polycyclic backbones were determined by NMR and ECD calculations, respectively. The plausible biosynthetic pathways of ganoaustralins A and B were proposed. Ganoaustralin B showed weak inhibition against β-secretase 1.

Cordycepin production by a novel endophytic fungus Irpex lacteus CHG05 isolated from Cordyceps hawkesii Gray

Cordycepin is an essential nucleoside antibiotic with a broad spectrum of physiological functions, which is currently produced by the fermentation of Cordyceps militaris. Even though numerous efforts were made to enhance cordycepin production, the cordycepin yield is still limited. High-cordycepin-yielding strains are still a prerequisite for industrial cordycepin production in large amounts. Screening high-cordycepin-yielding strains from other sources may break new grounds for cordycepin. In this study, Cordyceps hawkesii Gray, with high homology to C. militaris, was selected as the source to screen the cordycepin manufacturing endophytic fungi. Four isolates capable of cordycepin production were successfully obtained among all isolated endophytic fungi. One of the four with better cordycepin yield was identified as Irpex lacteus CHG05, which belongs to the Phlebia species. The response surface methodology was applied to optimize the culture conditions for cordycepin fermentation. 162.05 mg/L of cordycepin with a 53.1% improvement was achieved compared to the original conditions. This study indicates that the endophytic fungi from C. hawkesii Gray could produce cordycepin and served as the first report for cordycepin by the white-rot fungus of I. lacteus. Even though the yield is low compared to C. militaris, this strain provided another choice for enhanced cordycepin in the future.

Sesquiterpenes with diverse skeletons from histone deacetylase inhibitor modified cultures of the basidiomycete Cyathus stercoreus (Schwein.) De Toni HFG134

Epigenetic modifiers are proved to be effective specialized products-mining tools by rationally regulating the gene expression of fungal biosynthetic pathways. Chemical investigation on the histone deacetylase inhibitor (HDI) vorinostat (also known as SAHA)-modified cultures of the basidiomycete Cyathus stercoreus (Schwein.) De Toni (Nidulariaceae) led to the isolation of nine previously undescribed sesquiterpenes, and four previously described ones. The structures of the nine undescribed compounds were determined by extensive NMR spectroscopic analysis, HRESIMS analysis, as well as ECD and NMR calculations. Notably, the isolated sesquiterpenes are exclusive or overproduced from the epigenetic modified cultures compared to the negative control cultures. Additionally, the skeleton types of the isolated sesquiterpenes include protoilludalane, illudalane, 1,11-seco-protoilludalane, 10,11-seco-illudalane, and 14(11→10)abeo-illudalane. It is noteworthy that the 14(11→10)abeo-illudalane skeleton is reported for the first time. Cystercorodiol A, 4-O-acetylcybrodol, cystercorotone, and cybrodol showed weak inhibitory activity against the bacterium Escherichia coli ATCC25922 with the inhibitory rates 34.7%, 33.0%, 32.3%, and 29.6% at the concentration 200 μM, respectively. This study suggested that epigenetic modifiers are also an effective tool for specialized metabolite-mining in basidiomycetes.

Sesquiterpenoids and furan derivatives from the Orychophragmus violaceus (L.) O.E. Schulz endophytic fungus Irpex lacteus OV38

Nine undescribed compounds, including six tremulane-type sesquiterpenoids, irpexolaceus A-F, one phenolic bisabolane-type sesquiterpenoid, irpexolaceus G, and two furan derivatives, irpexonjust A-B, as well as eight known analogs, were isolated from an endophytic fungus (Irpex lacteus OV38) of Orychophragmus violaceus (L.) O.E. Schulz, a Chinese medicinal and edible plant. The structures of these natural compounds were elucidated based on NMR, HRESIMS, single-crystal X-ray diffraction, and ECD spectroscopic data. Among the tested isolates (50 μg/mL), the inhibitory effects of irpexolaceus A, C, D, F, and G, irpexonjust B, and irpexlacte B against NO release from LPS-induced RAW 264.7 cells were higher than 45%, while irpexlacte C (42.6%), irpexolaceus B (39.6%), irpexonjust A (43.7%), and irpexolaceus E (33.6%) exhibited weaker inhibitory effects on the release of NO.

Two new pyridine derivatives and two new furan derivatives from Irpex lacteus

Two undescribed disubstituted pyridine derivatives irpexidines A and B (1 and 2) and two undescribed alkylfuran derivatives irpexins K and L (3 and 4) were isolated from fermentation broth of Irpex lacteus. Their structures were established by extensive spectroscopic methods. The pyridine derivatives from this fungus were reported for the first time. The new compounds were evaluated for their cytotoxicity against Hela cancer cell and inhibitory activity on NO production.

Two new compounds from cultures of the basidiomycete Daedaleopsis tricolor

Two new compounds, daedatrin K (1) and 2-hydroxy-1-(5-(hydroxymethyl)furan-2-yl)propan-1-one (2), were isolated from cultures of the basidiomycetes Daedaleopsis tricolor. The new structures were elucidated on the basis of extensive spectroscopic methods. At the same time, two compounds were tested for their cytotoxicities against five human cancer cell lines. [Formula: see text].

Biotransformation of Huperzine A by Irpex lacteus-A fungal endophyte of Huperzia serrata

The biotransformation of huperzine A (hupA), one of the characteristic bioactive constituents of the medicinal plant Huperzia serrata, by a fungal endophyte of the host plant was studied. Two previously undescribed compounds 1-2, along with a known analog 8α,15α-epoxyhuperzine A (3), were isolated and identified. The structures of all the isolates were established by spectroscopic methods including NMR, MS, IR, and UV spectra. In particular, the absolute configurations of 1 and 2 were elucidated by CD spectra comparison and theoretic NOE strength calculation. In the LPS-induced neuro-inflammation injury assay, 1-3 exhibited moderate neuroprotective activity by increasing the viability of U251 cell lines with EC₅₀ values of 35.3 ± 0.9, 32.1 ± 0.9, and 50.3 ± 0.8 nM, respectively.