Chemical diversity and biological activities of specialized metabolites from the genus Chaetomium: 2013-2022

Unusual chaetoglobosins and a new type of ferroptosis inducer from an endophytic fungus Chaetomium sp. UJN-EF006

Seven unreported chaetoglobosin-type alkaloids, namely brachaetoglobosin A (1), chaetochalasins BF (2-6) and armochaeglobine C (7), together with the formerly described cytoglobosin C (8) and chaetoglobosin E (9), were obtained from an endophytic fungus Chaetomium sp. UJN-EF006 isolated from the leaves of Vaccinium bracteatum. Their structures were characterized through various spectral techniques including MS, NMR, X-ray crystallography and electronic circular dichroism. Also, this is only the second record of novel chaetochalasin and armochaeglobine skeletons of the cytochalasin super family, after 27 and 10 years of the first report, respectively. Compound 9 showed significant cytotoxic effect against two human tumor cell lines (MDA-MB231 and A549) and was identified as a new type of ferroptosis inducer (toward A549 cells) that could be used as a molecular tool in future related research.

Antifungal metabolites of biocontrol stain LB-1 and their inhibition mechanism against Botrytis cinerea

Introduction

Chaetomium subaffine LB-1 is a novel biocontrol strain that produces non-volatile metabolites that inhibit the growth of Botrytis cinerea. However, the specific metabolites and antimicrobial mechanism of the strain LB-1 remains unclear.

Methods

In this study, the antifungal substances produced by strain LB-1, as well as the underlying mechanism of its inhibitory effect against B. cinerea, were explored using metabolomic and transcriptomic analysis.

Results

The results found that 45 metabolites might be the key antifungal substances, such as ouabain, ferulic acid, chlorogenic acid, spermidine, stachydrine, and stearic acid. The transcriptomic analysis indicated that the inhibition effect of LB-1 on B. cinerea resulted in the upregulation of genes related to adenosine triphosphate (ATP)-binding cassette (ABC) transporters, peroxisome, ER stress, and multiple metabolic pathways, and in downregulation of many genes associated with the synthesis of cell walls/membranes, carbohydrate metabolism, cell cycle, meiosis, and DNA replication.

Discussion

These results suggested that the inhibitory effect of strain LB-1 against B. cinerea might be due to the destroyed cell wall and membrane integrity exerted by antimicrobial substances, which affect cell metabolism and inhibit cell proliferation.

Anti-inflammatory Polyketides from an Endophytic Fungus Chaetomium sp. UJN-EF006 of Vaccinium bracteatum

Seven new polyketides including three chromone derivatives (1-3) and four linear ones incorporating a tetrahydrofuran ring (4-7), along with three known compounds (8-10), were obtained from the fermentation of an endophytic fungus (Chaetomium sp. UJN-EF006) isolated from the leaves of Vaccinium bracteatum. The structures of these fungal metabolites have been elucidated by spectroscopic means including MS, NMR and electronic circular dichroism. A preliminary anti-inflammatory screening with the lipopolysaccharide (LPS) induced RAW264.7 cell model revealed moderate NO production inhibitory activity for compounds 1 and 4. In addition, the expression of three LPS-induced inflammatory factors IL-6, iNOS and COX-2 was also blocked by 1 and 4.

Changes in the soil fungal communities of steppe grasslands at varying degradation levels in North China

The grasslands in North China are rich in fungal resources. However, the knowledge of the structure and function of fungal communities and the role of microbial communities in vegetation restoration and succession are limited. Thus, we used an Illumina HiSeq PE250 high-throughput sequencing platform to study the changing characteristics of soil fungal communities in degraded grasslands, which were categorized as non-degraded (ND), lightly degraded, moderately degraded, and severely degraded (SD). Moreover, a correlation analysis between soil physical and chemical properties and fungal communities was completed. The results showed that the number of plant species, vegetation coverage, aboveground biomass, and diversity index decreased significantly with increasing degradation, and there were significant differences in the physical and chemical properties of the soil among the different degraded grasslands. The dominant fungal phyla in the degraded grassland were as follows: Ascomycota, 44.88%-65.03%; Basidiomycota, 12.68%-29.91%; and unclassified, 5.51%-16.91%. The dominant fungi were as follows: Mortierella, 6.50%-11.41%; Chaetomium, 6.71%-11.58%; others, 25.95%-36.14%; and unclassified, 25.56%-53.0%. There were significant differences in the microbial Shannon-Wiener and Chao1 indices between the ND and degraded meadows, and the composition and diversity of the soil fungal community differed significantly as the meadows continued to deteriorate. The results showed that pH was the most critical factor affecting soil microbial and fungal communities in SD grasslands, whereas soil microbial and fungal communities in ND grasslands were mainly affected by water content and other environmental factors.

Novel chlorinated and nitrogenated azaphilones with cytotoxic activities from the marine algal-derived fungus Chaetomium globosum 2020HZ23

Two novel chlorinated and nitrogenated azaphilones, namely N-butyl-2-aza-2-deoxychaetoviridin A (1) and N-hexyl-2-aza-2-deoxychaetoviridin A (2), along with a previously identified analogue, chaetoviridin A (3), were successfully obtained from Chaetomium globosum 2020HZ23, a marine algal-sourced endophytic fungus. The planar structures as well as the absolute configurations of these new metabolites were determined utilizing a synergistic approach that involved both spectroscopic techniques (1D/2D NMR and HRESIMS) and Density Functional Theory (DFT) calculations. Each compound was subject to in vitro cytotoxicity evaluation toward the A549 cancer cell line. Both compounds 1 and 2 demonstrated significant cytotoxicity, as evidenced by their respective IC50 values of 13.6 and 17.5 μM. Furthermore, 1 and 2 demonstrated potent cell migration inhibition, which elevated with increasing dose concentration. In contrast, compound 3 exhibited less cytotoxic activity relative to 1 and 2, suggesting that the cytotoxic potency escalates with N-substitution at the C-2 position and the introduction of a side chain. This finding could offer implications for future studies aimed at designing and refining lead compounds within this class.