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

Structural diversity of microbial secondary metabolites based on chemical epigenetic manipulation

Fungi are microorganisms with biosynthetic potential that are capable of producing a wide range of chemically diverse and biologically interesting small molecules. Chemical epigenetic manipulation has been increasingly explored as a simple and powerful tool to induce the production of additional microbial secondary metabolites in fungi. This review focuses on chemical epigenetic manipulation in fungi and summarizes 379 epigenetic manipulation products discovered from 2008 to 2022 to promote the discovery of their medicinal value.

Pestalotiopols E-J, Six New Polyketide Derivatives from a Marine Derived Fungus Pestalotiopsis sp. SWMU-WZ04-1

Chemical epigenetic cultivation of the sponge-derived fungus Pestalotiopsis sp. SWMU-WZ04-1 contributed to the identification of twelve polyketide derivatives, including six new pestalotiopols E-J (1-6) and six known analogues (7-12). Their gross structures were deduced from 1D/2D NMR and HRESIMS spectroscopic data, and their absolute configurations were further established by circular dichroism (CD) Cotton effects and the modified Mosher's method. In the bioassay, the cytotoxic and antibacterial activities of all compounds were evaluated. Chlorinated benzophenone derivatives 7 and 8 exhibited inhibitory effects on Staphylococcus aureus and Bacillus subtilis, with MIC values varying from 3.0 to 50 μg/mL. In addition, these two compounds were cytotoxic to four types of human cancer cells, with IC50 values of 16.2~83.6 μM. The result showed that compound 7 had the probability of being developed into a lead drug with antibacterial ability.

Secondary Metabolites of Bird's Nest Fungi: Chemical Structures and Biological Activities

Bird's nest fungi, a general term for species in the family Nidulariaceae, are named for their fruiting bodies that resemble bird's nests. Two of their members, Cyathus stercoreus (Schw.) de Toni. and Cyathus striatus Will. ex Pers., are known as medicinal fungi in Chinese medicine. Bird's nest fungi produce a variety of secondary metabolites that provide natural materials for screening and developing medicinal compounds. This review presents a systematic summary of the literature on the secondary metabolites of bird's nest fungi up to January 2023, including 185 compounds, mainly cyathane diterpenoids, with prominently characterized antimicrobial and antineurodegenerative activities. Our work aims to advance our understanding of bird's nest fungi and support studies on their natural product chemistry, pharmacology, and biosynthesis of secondary metabolites.

Recent Advances in Search of Bioactive Secondary Metabolites from Fungi Triggered by Chemical Epigenetic Modifiers

Genomic analysis has demonstrated that many fungi possess essential gene clusters for the production of previously unobserved secondary metabolites; however, these genes are normally reduced or silenced under most conditions. These cryptic biosynthetic gene clusters have become treasures of new bioactive secondary metabolites. The induction of these biosynthetic gene clusters under stress or special conditions can improve the titers of known compounds or the production of novel compounds. Among the inducing strategies, chemical-epigenetic regulation is considered a powerful approach, and it uses small-molecule epigenetic modifiers, which mainly act as the inhibitors of DNA methyltransferase, histone deacetylase, and histone acetyltransferase, to promote changes in the structure of DNA, histones, and proteasomes and to further activate cryptic biosynthetic gene clusters for the production of a wide variety of bioactive secondary metabolites. These epigenetic modifiers mainly include 5-azacytidine, suberoylanilide hydroxamic acid, suberoyl bishydroxamic acid, sodium butyrate, and nicotinamide. This review gives an overview on the method of chemical epigenetic modifiers to trigger silent or low-expressed biosynthetic pathways to yield bioactive natural products through external cues of fungi, mainly based on the research progress in the period from 2007 to 2022. The production of about 540 fungal secondary metabolites was found to be induced or enhanced by chemical epigenetic modifiers. Some of them exhibited significant biological activities such as cytotoxic, antimicrobial, anti-inflammatory, and antioxidant activity.

How to Completely Squeeze a Fungus-Advanced Genome Mining Tools for Novel Bioactive Substances

Fungal species have the capability of producing an overwhelming diversity of bioactive substances that can have beneficial but also detrimental effects on human health. These so-called secondary metabolites naturally serve as antimicrobial "weapon systems", signaling molecules or developmental effectors for fungi and hence are produced only under very specific environmental conditions or stages in their life cycle. However, as these complex conditions are difficult or even impossible to mimic in laboratory settings, only a small fraction of the true chemical diversity of fungi is known so far. This also implies that a large space for potentially new pharmaceuticals remains unexplored. We here present an overview on current developments in advanced methods that can be used to explore this chemical space. We focus on genetic and genomic methods, how to detect genes that harbor the blueprints for the production of these compounds (i.e., biosynthetic gene clusters, BGCs), and ways to activate these silent chromosomal regions. We provide an in-depth view of the chromatin-level regulation of BGCs and of the potential to use the CRISPR/Cas technology as an activation tool.

Feature-based molecular networking-guided discovery of siderophores from a marine mesophotic zone Axinellida sponge-associated actinomycete Streptomyces diastaticus NBU2966

Ten siderophore-related compounds were isolated by MS/MS-based molecular networking from a mesophotic sponge-associated Streptomyces diastaticus NBU2966. Among them, there were three kinds of siderophores including three undescribed phenol/thiazoline-type compounds, thiazostatin C, methyl thiazostatin B, and pulicatin J, one undescribed phenol/oxazoline-type compound, spoxazomicin E, and one undescribed phenol/oxazoline/thiazoline-type compound, streptochelin A, as well as five known compounds. Pulicatin J and spoxazomicin E were both isolated as a pair of inseparable epimers. The planar structures of all these compounds were determined based on the detailed NMR and HRESIMS spectroscopic analysis, and the absolute configurations of them were assigned by ECD and NMR quantum chemical calculations. Additionally, in vitro antibacterial activities, inhibition of MRSA biofilm formation, and neuroprotective activity for these compounds were tested.