Xylaridines C and D, Unusual Thiopyranodipyridine Alkaloids from the Fungus Xylaria longipes

Two new quinoline alkaloid with neuroprotective activities from Xylaria longipes

Two new quinoline alkaloids with an α, β-unsaturated amide side chain, xylarinines A and B (1 and 2), were isolated from the ethyl acetate extracts of Xylaria longipes solid fermentation. The structures of these were primarily determined though NMR and HRESIMS data analysis. The absolute configuration of compound 1 was assigned using experimental and calculated ECD data. The neuroprotective effects of compounds 1 and 2 against glutamate-induced damage in PC12 cells were evaluated in vitro bioassay. The results demonstrated that both compounds significantly improved cell viability, inhibited apoptosis, decreased malondialdehyde (MDA) levels, increased superoxide dismutase (SOD) and glutathione (GSH) levels, and reduced intracellular reactive oxygen species (ROS) accumulation. These findings suggested that these mechanisms contribute to the neuroprotective effects of the compounds.

Neuroprotective methylsuccinic acid and enoic acid derivatives from the fungus Xylaria longipes

Three undescribed methylsuccinic acid derivatives, xylaril acids A-C, and two undescribed enoic acid derivatives, xylaril acids D-E, were isolated from the fungus Xylaria longipes. The structures of the undescribed compounds were deduced by spectroscopic means, including HRESIMS and 1D/2D NMR spectroscopy, as well as ECD calculations. The absolute configuration of xylaril acids A was further determined by single-crystal X-ray diffraction experiments. All the isolated compounds displayed neuroprotective activities against oxygen-glucose deprivation/reperfusion injury in PC12 cells by enhancing cell viability and inhibiting cell apoptosis.

Sulfur-Containing Metabolites from Marine and Terrestrial Fungal Sources: Origin, Structures, and Bioactivities

Organosulfur natural products (NPs) refer to the different kinds of small molecular-containing sulfur (S) elements. Sulfur-containing NPs tightly link to the biochemical processes and play an important role in the pharmaceutical industry. The majority of S-containing NPs are generally isolated from Alliaceae plants or bacteria, and those from fungi are still relatively rare. In recent years, an increasing number of S-containing metabolites have been discovered in marine and terrestrial fungi, but there is no comprehensive and targeted review to summarize the studies. In order to make it more straightforward to better grasp the fungal-derived S-containing NPs and understand the particularity of marine S-containing NPs compared to those from terrestrial fungi, we summarized the chemical structures and biological activities of 89 new fungal-derived S-containing metabolites from 1929 when the penicillin was discovered to the present in this current review. The structural and bioactive diversity of these S-containing metabolites were concluded in detail, and the preliminary mechanism for C-S bond formation in fungi was also discussed briefly.

Secondary Metabolites from Fungi-In Honor of Prof. Dr. Ji-Kai Liu's 60th Birthday

It is our pleasure and privilege to serve as Guest Editors for this Special Issue of the Journal of Fungi in honor of Professor Ji-Kai Liu's 60th birthday [...].

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world’s most successful pharmaceuticals and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage “If you don’t seek, you don’t find”. Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.

Xylarinaps A-E, five pairs of naphthalenone derivatives with neuroprotective activities from Xylaria nigripes

Five pairs of undescribed naphthalenone derivative enantiomers, xylarinaps A-E, including one pair of indole naphthalenones and four pairs of naphthalene-naphthalenone dimers, were isolated from the ethyl acetate extracts of the solid fermentation of Xylaria nigripes, which has been used as a traditional Chinese medicinal fungus for the treatment of insomnia, trauma, and depression. The structures of these enantiomers were elucidated based on comprehensive spectroscopic analysis, including NMR and HRESIMS. Their absolute configurations were assigned by the experimental and calculated ECD data. The neuroprotective effects of all the compounds against damage to PC12 cells by oxygen and glucose deprivation (OGD) were evaluated by an in vitro bioassay. The results revealed that xylarinaps A, B, D, and E significantly enhanced cell viability, decreased the levels of malondialdehyde (MDA), increased the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), as well as further markedly inhibiting apoptosis, which indicated that these results could be the mode of action of their neuroprotective effect.

Four new resorcinol derivatives with neuroprotective activities from Xylaria nigripes

Four new resorcinol derivatives, namely (-)/(+)-xylarinig A (1), as well as xylarinigs B (2) and C (3), were isolated from the ethyl acetate extracts of the solid fermentation of Xylaria nigripes. Their structures were established by comprehensive spectroscopic analysis combined with electronic circular dichroism (ECD) calculations. Compound 1 is an optical mixture, and was resoluted into optical pure enatiomers (+)-1 and (-)-1 by chiral HPLC. The neuroprotective effects of 1-3 against the damage of PC12 cells induced by oxygen and glucose deprivation (OGD) were evaluated.

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.

Survey of natural products reported by Asian research groups in 2019

The new natural products reported in 2019 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2019 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Dipleosporalones A and B, Dimeric Azaphilones from a Marine-Derived Pleosporales sp. Fungus

Dipleosporalones A and B (1 and 2), two new [2 + 2] azaphilone dimers, were obtained from a marine-derived Pleosporales sp. fungus. The absolute configurations of 1 and 2 were elucidated by calculations of their ECD spectra. Dipleosporalone A (1) possessed an unprecedented skeleton with an uncommon 6/4/6 ring system. Compounds 1 and 2 showed cytotoxicity about 30-90-fold more potent than that of their monomer pinophilin B.

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

Xylarilongipins A and B, along with their biosynthetic precursor hymatoxin L, were isolated from the culture broth of the fungicolous fungus Xylaria longipes HFG1018 inhabiting in the medicinal fungus Fomitopsis betulinus.

Hot off the press

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as phlegmadine A from Phlegmariurus phlegmaria.