Xylaropyrones B and C, new γ-pyrones from the endophytic fungus Xylaria sp. SC1440

Six Unprecedented Cytochalasin Derivatives from the Potato Endophytic Fungus Xylaria curta E10 and Their Cytotoxicity

Six previously undescribed cytochalasins, Curtachalasins X1-X6 (1-6), together with six known compounds (7-12) were isolated from the endophytic fungus Xylaria curta E10 harbored in the plant Solanum tuberosum. The structures were elucidated by the interpretation of HRESIMS, UV, and NMR data. The absolute configurations of Curtachalasins X1-X6 were determined by comparison of their experimental and calculated electronic circular dichroism (ECD) spectra. In bioassays, Curtachalasin X1 (1) and X5 (5) showed cytotoxic activity against the MCF-7 cell line with IC50 values of 2.03 μM and 0.85 μM, respectively.

Antioxidant Activity and Cytotoxicity against Cancer Cell Lines of the Extracts from Novel Xylaria Species Associated with Termite Nests and LC-MS Analysis

Xylaria species associated with termite nests or soil have been considered rare species in nature and the few which have been reported upon have been found to act as a rich source of bioactive metabolites. This study evaluated 10 ethyl acetate extracts of five new Xylaria species associated with termite nests or soil for their antioxidant activity, and cytotoxicity against different cancer and normal cell lines. DPPH and ABTS radical scavenging activities of the extracts demonstrated strong capacity with low IC₅₀ values. The highest observed activities belonged to X. vinacea SWUF18-2.3 having IC₅₀ values of 0.194 ± 0.031 mg/mL for DPPH assay and 0.020 ± 0.004 mg/mL for ABTS assay. Total phenolic content ranged from 0.826 ± 0.123 to 3.629 ± 0.381 g GAE/g crude extract which correlated with antioxidant activities. The high total phenolic content could contribute to the high antioxidant activities. Cytotoxicity was recorded against A549, HepG2, HeLa and PNT2 and resulted in broad spectrum to specific activity depending on the cell lines. The highest activities were observed with X. subintraflava SWUF16-11.1 which resulted in 11.15 ± 0.32 to 13.17 ± 2.37% cell viability at a concentration of 100 µg/mL. Moreover, LC-MS fingerprints indicated over 61 peaks from all isolates. There were 18 identified and 43 unidentified compounds compared to mass databases. The identified compounds were from various groups of diterpenoids, diterpenes, cytochalasin, flavones, flavonoids, polyphenols, steroids and derivatives, triterpenoids and tropones. These results indicate that Xylaria spp. has abundant secondary metabolites that could be further explored for their therapeutic properties.

Diversity of fungal isolates from fungus-growing termite Macrotermes barneyi and characterization of bioactive compound from Xylaria escharoidea

Owing to their potential applications, as well as their structural diversity, the discovery of novel secondary metabolites from insect-associated fungi has been of interest to researchers in recent years. The aim of this study was therefore to estimate the diversity of fungi associated with fungus-growing termites and bioprospecting these for potential secondary metabolites. In total, 18 fungal species were isolated and described from the gut and comb of Macrotermes barneyi based on 18S ribosomal DNA gene sequence analysis. Antimicrobial activity assays were carried out on all the known fungi, and nine isolates were recorded as active against pathogenic fungi. Xylaria escharoidea, the best performing isolate, was grown at laboratory scale and 4,8-dihydroxy-3,4-dihydronaphthalen-1(2H) was isolated and characterized. The minimum inhibitory concentration of this isolated compound against tested pathogenic organisms was found to be 6.25 μg. In addition, molecular docking studies have revealed that 4,8-dihydroxy-3,4-dihydronaphthalen-1(2H) is a prominent antibacterial agent with a marked interaction with key residues on protein A (agrA_C ) that regulates the accessory gene. The findings of this study support the drug discovery of antimicrobial properties in insect-associated fungi, which may lead to novel secondary metabolites.

Recent progress in biodiversity research on the Xylariales and their secondary metabolism

The families Xylariaceae and Hypoxylaceae (Xylariales, Ascomycota) represent one of the most prolific lineages of secondary metabolite producers. Like many other fungal taxa, they exhibit their highest diversity in the tropics. The stromata as well as the mycelial cultures of these fungi (the latter of which are frequently being isolated as endophytes of seed plants) have given rise to the discovery of many unprecedented secondary metabolites. Some of those served as lead compounds for development of pharmaceuticals and agrochemicals. Recently, the endophytic Xylariales have also come in the focus of biological control, since some of their species show strong antagonistic effects against fungal and other pathogens. New compounds, including volatiles as well as nonvolatiles, are steadily being discovered from these ascomycetes, and polythetic taxonomy now allows for elucidation of the life cycle of the endophytes for the first time. Moreover, recently high-quality genome sequences of some strains have become available, which facilitates phylogenomic studies as well as the elucidation of the biosynthetic gene clusters (BGC) as a starting point for synthetic biotechnology approaches. In this review, we summarize recent findings, focusing on the publications of the past 3 years.

A new alkynol compound from Platycodins folium and its cytotoxicity

A new alkynol, platycodynol (1), identified as 2, 3, 9, 13, 14-pentahydroxy-4, 6-tetradecadiyne, along with six known compounds (2-7) were obtained from Platycodins folium for the first time. Their structures were elucidated with infrared (IR), ultraviolet (UV), 1D and 2D nuclear magnetic resonance (NMR) spectroscopic analysis as well as by high resolution electrospray ionization mass spectroscopy (HRESIMS). Platycodynol showed cytotoxicity against S180, A549 and SPC-A-1 cancer cells but no cytotoxicity against normal cells NCTC1469 and HL-7702 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method.

A new cytochalasin derivative from the mangrove-derived endophytic fungus Xylaria sp. HNWSW-2

A new cytochalasin derivative xylarisin B (1), together with four known compounds astropyrone (2), guaidiol (3), xylaropyrone B (4), and xylaropyrone C (5), were isolated from the fermentation broth of Xylaria sp. HNWSW-2. Their structures were elucidated by spectroscopic data. Among them, compounds 2 and 3 at a concentration of 50 μg/ml showed weak inhibitory activity against AChE with inhibition rates of 10.4 and 12.9%, respectively. In addition, compound 2 also exhibited inhibitory activity against α-glycosidase with inhibition rate of 77.0% at a concentration of 0.25 mg/ml.

Chemical constituents and cytotoxic activity from the wood-decaying fungus Xylaria sp. SWUF08-37

A new cyclic pentapeptide, pentaminolarin (1), and a new cytochalasin, xylochalasin (2), along with thirteen known compounds (3-15) were isolated from the wood-decaying fungus Xylaria sp. SWUF08-37. The absolute configurations of 1 were determined by a combination of Marfey's method and TDDFT ECD calculation and the absolute configurations of 2 were established by TDDFT ECD calculation. Compound 12 showed moderate cytotoxicity against HeLa (IC₅₀ = 19.60 µg/mL), HT29 (IC₅₀ = 17.31 µg/mL), HCT116 (IC₅₀ = 14.28 µg/mL), MCF-7 (IC₅₀ = 15.38 µg/mL), and Vero (IC₅₀ = 24.97 µg/mL) cell lines by MTT assay. Compounds 1 and 2 showed slight cytotoxicity against all tested cancer cell lines.