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.

Comparison of Antioxidant Properties and Metabolite Profiling of Acer pseudoplatanus Leaves of Different Colors.

Acer pseudoplatanus (maple) is a widely grown ornamental plant. In addition to its ornamental and ecological value, it also has potentially high economic value. It is a rich source of polyphenols and exhibits antioxidant activity. However, the relationship between polyphenol content and antioxidant activity in maple leaves of different colors (green, yellow, and red) has not yet been investigated. In this study, the total polyphenol (TP), total flavonoid (TFlav), tannin (TET), chlorophyll a and b (Chl a and b), total anthocyanin (TAN), and total carotene (TAC) contents in maple leaves of different colors were evaluated. Their antioxidant activities were determined based on the inhibition of lipid oxidation, DPPH scavenging, ferric ion-reducing antioxidant power, and iron-chelating abilities. The concentrations of TP, TET, TFlav, TAN, and TAC in red maple leaves were higher than those in green and yellow maple leaves. In addition, red maple leaves showed a higher antioxidant effect than the leaves of the other two colors. We observed that antioxidant activity was positively correlated with TP, TFlav, and TAN and negatively correlated with Chl a and b. Finally, we analyzed the metabolites of the different colored (i.e., green, yellow, and red) maple leaves using gas chromatography/mass spectrometry (GC/MS) and found that the metabolite profile significantly varied between the different colors. These results suggest that red leaves are a good source of polyphenols and antioxidants and have potential use in the development of functional foods and medicinal applications.

Diterpenes with bicyclo[2.2.2]octane moieties from the fungicolous fungus Xylaria longipes HFG1018.

Xylarilongipins A (1) and B (2), two diterpenes each with an unusual cage-like bicyclo[2.2.2]octane moiety, along with their biosynthetic precursor hymatoxin L (3), were isolated from the culture broth of the fungicolous fungus Xylaria longipes HFG1018 inhabiting in the medicinal fungus Fomitopsis betulinus. The structures and absolute configurations of the three compounds were established by extensive spectroscopic analysis and single-crystal X-ray diffraction analysis. Xylarilongipin A (1) displayed moderate inhibitory activity against the cell proliferation of concanavalin A-induced T lymphocytes and lipopolysaccharide-induced B lymphocytes with IC50 values of 13.6 and 22.4 µM, respectively. Additionally, the biosynthetic pathways for compounds 1-3 are discussed. This work not only corroborates the structure of the 9,16-cyclo-(18-nor-)isopimarane skeleton by single-crystal X-ray diffraction analysis for the first time, but also provides new insights into the biosynthetic origin of the unusual diterpene skeletons.