Development of an enzyme linked immunosorbent assay for detection of cyathane diterpenoids

Natural and engineered xylosyl products from microbial source

Glycosylation is a prevalent post-modification found in natural products and has a significant impact on the structural diversity and activity variation of natural products. Glucosylation is the most common type of glycosylation, whereas xylosylation is relatively rare. Despite their unique chemical structures and beneficial activities, xylosylated natural products from microorganisms have received little attention. This review provides, for the first time, a comprehensive summary of 126 microbial-derived xylosylated natural products, including xylosyl-cyathane diterpenes, xylosylated triterpenes, xylosyl aromatic compounds, and others. Among these compounds, xylosyl-cyathane diterpenes represent the highest number of derivatives, followed by xylosylated triterpenes. Xylosyl compounds from bacterial sources have less defined structural profiles compared to those from fungi. The characterization of xylosyltransferase EriJ from Basidiomycota extended the structural diversity of xylosyl cyathane diterpenes. This work provides a valuable reference for the research and use of xylosyltransferase for drug discovery and synthetic chemistry. Further work is needed to explore the potential applications of microbial derived xylosyl compounds and to develop novel xylosyl transferases. With the deepening of genomic sequencing of medicinal fungi, more biosynthesis of bioactive xylosyl compounds is expected to be elucidated in the future.

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.

Erinacine A and related cyathane diterpenoids: Molecular diversity and mechanisms underlying their neuroprotection and anticancer activities

The presence of a fused 5/6/7 tricyclic core characterizes the group of cyathane diterpene natural products, that include more than 170 compounds, isolated from fungi such as Cyathus africanus and Hericium erinaceus. These compounds have a common biosynthetic precursor (cyatha-3,12-diene) and can be produced bio- or hemi-synthetically, or via total syntheses. Cyathane diterpenes display a range of pharmacological properties, including anti-inflammatory (possibly through binding to the iNOS protein) and neuroprotective effects. Many cyathanes like cyahookerin C, cyathin Q and cyafranines B and G can stimulate neurite outgrowth in cells, whereas conversely a few molecules (such as scabronine M) inhibit NGF-stimulated neurite outgrowth. The main anticancer cyathanes are erinacine A and cyathins Q and R, with a capacity to trigger cancer cell death dependent on the production of reactive oxygen species (ROS). These compounds, active both in vitro and in vivo, activate different signaling pathways in tumor cells to induce apoptosis (and autophagy) and to upregulate the expression of several proteins implicated in the organization and functioning of the actin cytoskeleton. An analysis of the functional analogy between erinacine A and other natural products known to interfere with the actin network in a ROS-dependent manner (notably cucurbitacin B) further supports the idea that erinacine A functions as a perturbator of the cytoskeleton organization. Collectively, we provide an overview of the molecular diversity of cyathane diterpenes and the main mechanisms of action of the lead compounds, with the objective to encourage further research with these fungal products. The anticancer potential of erinacine A deserves further attention but it will be necessary to better characterize the implicated targets and signaling pathways.

Proteome analysis provides insight into the regulation of bioactive metabolites in Hericium erinaceus

BACKGROUND

Hericium erinaceus, a famous edible mushroom, is also a well-known traditional medicinal fungus. To date, a large number of bioactive metabolites with antitumor, antibacterial, and immune-boosting effects were isolated from the free-living mycelium and fruiting body of H. erinaceus.

OBJECTIVE

Here we used the proteomic approach to explore proteins involved in the regulation of bioactive metabolites, including terpenoid, polyketide, sterol and etc. RESULTS: Using mass spectrometry, a total of 2543 unique proteins were identified using H. erinaceus genome, of which 2449, 1855, 1533 and 690 proteins were successfully annotated in Nr, KOG, KEGG and GO databases. Among them, 722 proteins were differentially expressed (528 up- and 194 down-regulated) in fruiting body compared with mycelium. Most of differentially expressed proteins were putatively involved in energy metabolism, molecular signaling, and secondary metabolism. Additionally, numerous proteins involved in terpenoid, polyketide, and sterol biosynthesis were identified. Our data revealed that proteins involved in polyketide biosynthesis were up-regulated in the fruiting body, while some proteins in mevalonate (MEP) pathway from terpenoid biosynthesis were generally up-regulated in mycelium.

CONCLUSIONS

The present study suggested that the differential regulation of biosynthesis genes could produce various bioactive metabolites with pharmacological effects in H. erinaceus.

Quality control of antibodies for assay development

Antibodies are used as powerful tools in basic research, for example, in biomarker identification, and in various forms for diagnostics, for example, identification of allergies or autoimmune diseases. Due to their robustness and ease of handling, immunoassays are favourite methods for investigation of various biological or medical questions. Nevertheless in many cases, additional analyses such as mass spectrometry are used to validate or confirm the results of immunoassays. To minimize the workload and to increase confidence in immunoassays, there are urgent needs for antibodies which are both highly specific and well validated. Unfortunately many commercially available antibodies are neither well characterized nor fully tested for cross-reactivities. Adequate quality control and validation of an antibody is time-consuming and can be frustrating. Such validation needs to be performed for every assay/application. However, where an antibody validation is successful, a highly specific and stable reagent will be on hand. This article describes the validation processes of antibodies, including some often neglected factors, as well as unspecific binding to other sample compounds in a multiparameter diagnostic assay. The validation consists of different immunological methods, with important assay controls, and is performed in relation to the development of a diagnostic test.

Production of cyathane type secondary metabolites by submerged cultures of Hericium erinaceus and evaluation of their antibacterial activity by direct bioautography

Background

Fungi of the phylum Basidiomycota are well-known to form a broad spectrum of biologically active secondary metabolites, especially low molecular weight compounds such as terpenoids. Hericium erinaceus produces various cyathane type diterpenoids including erinacines. However, no quantitative data and production kinetics have been reported on the biosynthesis of the erinacines C and P in submerged cultures. In the present study, the production of erinacine C was optimized, and the product formation kinetics as well as the antimicrobial activity were studied by high-performance liquid chromatography (HPLC), high-performance thin-layer chromatography (HPTLC) and direct bioautography.

Results

Oatmeal and Edamin^® K were identified to be crucial media components for an efficient production of erinacine C. The highest concentrations of erinacine C were obtained in the optimized culture medium on the 9^th culture day (approximately 260 mg L⁻¹). The production of erinacine P was strongly time dependent. The maximum concentration of erinacine P of 184 mg L⁻¹ was observed on the third culture day. Afterwards, the concentrations of erinacine P decreased while the concentrations of erinacine C steadily increased. Comparable results were obtained by HPTLC with UV detection and HPLC with diode-array detection (DAD) analyses. Direct bioautography allowed for an additional analysis of the antimicrobial activity of the secondary metabolites.

Conclusions

The C and N sources oatmeal and Edamin^® K induced the formation of erinacine C. Detailed product formation kinetics of the erinacines C and P have been reported for the first time. HPTLC combined with the Aliivibrio fischeri bioassay allowed for an instant detection of cyathane diterpenoids in crude extracts and for an evaluation of the antimicrobial activity of the secondary metabolites directly on the plate.

Electronic supplementary material

The online version of this article (doi:10.1186/s40694-015-0018-y) contains supplementary material, which is available to authorized users.