| Summary: | As part of ongoing systematic research into the discovery of bioactive secondary metabolites with novel structures from Korean wild mushrooms, we investigated secondary metabolites from a poisonous mushroom, <i>Omphalotus japonicus</i> (Kawam.) Kirchm. & O. K. Mill. belonging to the family Marasmiaceae, which causes nausea and vomiting after consumption. The methanolic extract of <i>O. japonicus</i> fruiting bodies was subjected to the fractionation by solvent partition, and the CH<sub>2</sub>Cl<sub>2</sub> fraction was analyzed for the isolation of bioactive compounds, aided by an untargeted liquid chromatography mass spectrometry (LC–MS)-based analysis. Through chemical analysis, five fatty acid derivatives (<b>1</b>–<b>5</b>), including two new fatty acid derivatives, omphalotols A and B (<b>1</b> and <b>2</b>), were isolated from the CH<sub>2</sub>Cl<sub>2</sub> fraction, and the chemical structures of the new compounds were determined using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and high resolution electrospray ionization mass spectrometry (HR-ESIMS), as well as fragmentation patterns in MS/MS data and chemical reactions followed by the application of Snatzke’s method and competing enantioselective acylation (CEA). In the anti-<i>Helicobacter pylori</i> activity test, compound <b>1</b> showed moderate antibacterial activity against <i>H. pylori</i> strain 51 with 27.4% inhibition, comparable to that of quercetin as a positive control. Specifically, compound <b>3</b> exhibited the most significant antibacterial activity against <i>H. pylori</i> strain 51, with MIC<sub>50</sub> and MIC<sub>90</sub> values of 9 and 20 μM, respectively, which is stronger inhibitory activity than that of another positive control, metronidazole (MIC<sub>50</sub> = 17 μM and MIC<sub>90</sub> = 46 μM). These findings suggested the experimental evidence that the compound <b>3</b>, an α,β-unsaturated ketone derivative, could be used as a moiety in the development of novel antibiotics against <i>H. pylori</i>.
|
|---|