New meroterpenoid compounds from the culture of mushroom Panus lecomtei

Isolation, structural elucidation and biosynthetic pathway of bioactive prenyl quinone compounds from Panus lecomtei based on untargeted metabolomics combined with molecular networking

Panus lecomtei is a relatively unfamiliar and undeveloped mushroom. This study generated ethyl acetate extracts of P. lecomtei intracellular (I), extracellular (E) and total fermentation broth (T). Both E and T extracts demonstrated antioxidant and antibacterial activities at 100 to 200 μg/mL. The composition differences of metabolites of these extracts were further studied based on comparative metabolomics by LS/MS and molecular network analysis. The results revealed that there were over 2000 significantly distinct metabolites among the three extracts, with abundant prenyl quinone compounds. Furthermore, the molecular network clarified the conversion relationship of P. lecomtei metabolites. Seven known prenyl quinone derivatives (1-7) were isolated from the E extract. Among them, compound 3 displayed excellent antioxidant activity and modest antibacterial activity. Compound 5 was discovered in fungi for the first time. Finally, a potential biosynthetic route for prenyl quinone in P. lecomtei was suggested.

Precursor-Directed Biosynthesis of Panepoxydone Derivatives with Nitric Oxide Production Inhibitory Activity

Panepoxydone is a natural NF-κB inhibitor isolated from basidiomycetes belonging to the genus Panus and Lentinus. It is biosynthesized from prenylhydroquinone through successive hydroxylation, epoxidation, and reduction reactions. In this study, we establish an efficient precursor-directed biosynthesis strategy for the structural expansion of panepoxydone based on its biosynthetic pathway. Supplementation of the panepoxydone-producing strain, Panus rudis, with various prenylhydroquinone analogues enabled the production of fourteen previously undescribed panepoxydone derivatives, panepoxyquinoid A-N (2-14). The obtained panepoxydone derivatives together with their parental molecules were evaluated for their inhibitory activity on LPS-induced NO production in RAW 264.7 cells. Compounds 1, 5-6, 10-11, and 14-15 displayed significant suppressive effects on LPS-induced NO production with IC50 values ranging from 4.3 to 30.1 μM.

A Mushroom P450-Monooxygenase Enables Regio- and Stereoselective Biocatalytic Synthesis of Epoxycyclohexenones

An epoxycyclohexenone (ECH) moiety occurs in natural products of both bacteria and ascomycete and basidiomycete fungi. While the enzymes for ECH formation in bacteria and ascomycetes have been identified and characterized, it remained obscure how this structure is biosynthesized in basidiomycetes. In this study, we i) identified a genetic locus responsible for panepoxydone biosynthesis in the basidiomycete mushroom Panus rudis and ii) biochemically characterized PanH, the cytochrome P450 enzyme catalyzing epoxide formation in this pathway. Using a PanH-producing yeast as a biocatalyst, we synthesized a small library of bioactive ECH compounds as a proof of concept. Furthermore, homology modeling, molecular dynamics simulation, and site directed mutation revealed the substrate specificity of PanH. Remarkably, PanH is unrelated to ECH-forming enzymes in bacteria and ascomycetes, suggesting that mushrooms evolved this biosynthetic capacity convergently and independently of other organisms.

Optimization for the production of a polyketone 3S,4S-DMD from Panus lecomtei (Agaricomycetes) by submerged fermentation

3,4-Dihydroxy-2,2-dimethyl-chroman derivatives have diverse physiological properties. A polyketone (3S,4S)-3,4-Dihydroxy-6-methoxy-2,2-dimethylchromom (3S,4S-DMD) with antibacterial activity was isolated from the solid culture of rare edible fungus Panus lecomtei. However, the yield of 3S,4S-DMD in solid culture of P. lecomtei is very low and the production period are too long. In this work, efficient accumulation of 3S,4S-DMD in P. lecomtei by submerged fermentation is studied. The key fermentation factors of P. lecomtei for 3S,4S-DMD production were optimised by single-factor experiment successively, and then a Box-Behnken design (BBD) experiment was carried out to further enhance 3S,4S-DMD production. A maximum 3S,4S-DMD yield of 196.3 mg/L was obtained at 25.78 g/L glucose, 1.67 g/L MgSO₄ · 7H₂O, 40°C and 197 r/min, respectively, which increased by 1.3-fold in comparison with that in the non-optimised fermentation conditions. Furthermore, an enhanced yield of 3S,4S-DMD (261.6 mg/L) was obtained in 5-L agitated fermenter. The 3S,4S-DMD productivity in flask and fermenter reached to 7.26 and 8.07 mg/g per day, respectively, which considerably increased by over 121-fold in comparison with that in the solid fermentation (0.06 mg/g per day). This study presents a potential method for the production of 3S,4S-DMD by submerged fermentation.

Meroterpenoids: A Comprehensive Update Insight on Structural Diversity and Biology

Meroterpenoids are secondary metabolites formed due to mixed biosynthetic pathways which are produced in part from a terpenoid co-substrate. These mixed biosynthetically hybrid compounds are widely produced by bacteria, algae, plants, and animals. Notably amazing chemical diversity is generated among meroterpenoids via a combination of terpenoid scaffolds with polyketides, alkaloids, phenols, and amino acids. This review deals with the isolation, chemical diversity, and biological effects of 452 new meroterpenoids reported from natural sources from January 2016 to December 2020. Most of the meroterpenoids possess antimicrobial, cytotoxic, antioxidant, anti-inflammatory, antiviral, enzyme inhibitory, and immunosupressive effects.