Ketoreductase Domain-Catalyzed Polyketide Chain Release in Fungal Alkyl Salicylaldehyde Biosynthesis

DMSO enhances the biosynthesis of epoxyquinols in Pestalotiopsis sp. (strain IQ-011) and yields new [4 + 2] cycloaddition dimers

Pestalotiopsis sp. (strain IQ-011) produces cuautepestalorin (10), a 7,8-dihydrochromene-oxoisochromane adduct featuring a spiro-polycyclic (6/6/6/6/6/6) ring system. Additionally, it yields its proposed biosynthetic precursors: cytosporin M (1) and oxopestalochromane (11) when cultured under standard conditions (fermentation in solid media). Following an OSMAC approach guided by metabolomic studies (PCA and molecular networks), it was established that the epigenetic modulator DMSO dramatically increases the production of 1 up to 50 times according to feature-based molecular networking (FBMN) analysis, and triggers the production of other derivatives from the epoxyquinol family. Chemo-targeted isolation resulted in the discovery of four new compounds: 19-hydroxycytosporin M (2) and three [4 + 2] cycloaddition products: ent-eutyscoparol J (4), ent-pestaloquinol A (6) and ent-pestaloquinol B (8). The structures of all isolates were established based on spectroscopic, spectrometric, chiroptical, and X-ray diffraction analyses. This study demonstrates the potential of combining metabolomic tools with DMSO as an epigenetic modulator to enhance fungal metabolite diversity and highlights the importance of chiroptical methods for accurate compound identification.

Synthetic Biology in Natural Product Biosynthesis

Synthetic biology has played an important role in the renaissance of natural products research during the post-genomics era. The development and integration of new tools have transformed the workflow of natural product discovery and engineering, generating multidisciplinary interest in the field. In this review, we summarize recent developments in natural product biosynthesis from three different aspects. First, advances in bioinformatics, experimental, and analytical tools to identify natural products associated with predicted biosynthetic gene clusters (BGCs) will be covered. This will be followed by an extensive review on the heterologous expression of natural products in bacterial, fungal and plant organisms. The native host-independent paradigm to natural product identification, pathway characterization, and enzyme discovery is where synthetic biology has played the most prominent role. Lastly, strategies to engineer biosynthetic pathways for structural diversification and complexity generation will be discussed, including recent advances in assembly-line megasynthase engineering, precursor-directed structural modification, and combinatorial biosynthesis.

Formation of N-Hydroxyethylisoindolinone Derivatives in Fungi Requires Highly Coordinated Consecutive Oxidation Steps

Gene duplication significantly contributes to the diversification of biosynthetic potential and increases the structural diversity of secondary metabolites. Here, we report the second alkyl salicylaldehyde derivative biosynthetic gene cluster in Penicillium roqueforti, being responsible for the formation of ethanolamine-containing derivatives. Heterologous expression and feeding experiments provided evidence for their formation via collaboration and modification with one cytochrome P450 and two flavin-containing monooxygenases in a highly ordered manner before and after ethanolamine incorporation.

Chromones Featuring a [6,6]-Spiroketal Moiety Produced by Coculture of the Endophytic Fungi Chaetomium virescens and Xylaria Grammica

Under the guidance of HPLC-DAD analysis, ten new chromones featuring a rare [6,6]-spiroketal moiety, namely chaetovirexylariones A-J (1-10), together with two known congeners (11-12), were isolated from coculture of the endophytic fungi Chaetomium virescens and Xylaria grammica, from the rhizome of the medicinal plant Smilax glabra Roxb. Their structures were elucidated via a combination of NMR and HRESIMS data, and the absolute configurations of 1-10 were determined by the chemical conversion and single-crystal X-ray diffraction (Cu Kα) experiments, as well as the comparison of the experimental and calculated electronic circular dichroism (ECD) data. Compound 6 is the first report as a racemate of this type of natural product. Compound 10 represents the first example of a [6,6]-spiroketal chromone bearing a 5-amino-3-methyl-2-pentenoic acid fragment. Compound 8 demonstrated a reduction in PTX resistance of SW620/AD300 by a factor of 45, and had the potential to be an effective P-gp inhibitor and an antitumor chemotherapy sensitizer.

Cupin-domain containing protein is not essential for the alkyl salicylaldehyde formation in Aspergillus ustus

Previous studies demonstrated the requirement of four enzymes including a cupin-domain containing protein for the formation of alkyl salicylaldehydes and derivatives. Heterologous expression of three biosynthetic genes from Aspergillus ustus resulted in the formation of such compounds in high-yields without involvement of a cupin analogue.

Penisimplicins A and B: Novel Polyketide-Peptide Hybrid Alkaloids from the Fungus Penicillium simplicissimum JXCC5

In this study, two previously undescribed nitrogen-containing compounds, penisimplicins A (1) and B (2), were isolated from Penicillium simplicissimum JXCC5. The structures of 1 and 2 were elucidated on the basis of comprehensive spectroscopic data analysis, including 1D and 2D NMR and HRESIMS data. The absolute configuration of 2 was determined by Marfey's method, ECD calculation, and DP4+ analysis. Both structures of 1 and 2 feature an unprecedented manner of amino acid-derivatives attaching to a polyketide moiety by C-C bond. The postulated biosynthetic pathways for 1 and 2 were discussed. Additionally, compound 1 exhibited significant acetylcholinesterase inhibitory activity, with IC50 values of 6.35 μM.

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 clavirolide L from Clavularia viridis.