Identification of Antibacterial Sterols from Korean Wild Mushroom via Bioactivity- and LC-MS/MS Profile-Guided Fractionation.

As part of an ongoing natural product chemical research for the discovery of bioactive secondary metabolites with novel structures, wild fruiting bodies of were collected and subjected to chemical and biological analyses. We subjected the fractions derived from the methanol extract of the fruiting bodies of to bioactivity-guided fractionation because the methanol extract of showed antibacterial activity against strain 51, according to our bioactivity screening. The -hexane and dichloromethane fractions showed moderate to weak antibacterial activity against strain 51, and the active fractions were analyzed for the isolation of antibacterial compounds. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that the -hexane fraction contains several compounds which are absent in the other fractions, so the fraction was prioritized for further fractionation. Through chemical analysis of the active -hexane and dichloromethane fractions, we isolated five ergosterol derivatives (-), and their chemical structures were determined to be demethylincisterol A (), (20,22,24)-ergosta-7,22-dien-3β,5α,6β-triol (), (24)-ergosta-7-ene-3β,5α,6β-triol (), 5α,6α-epoxy-(22,24)-ergosta-7,22-dien-3β-ol (), and 5α,6α-epoxy-(24)-ergosta-7-en-3β-ol () by NMR spectroscopic analysis. This is the first report on the presence of ergosterol derivatives (-) in . Compound showed the most potent anti- activity with 33.9% inhibition, rendering it more potent than quercetin, a positive control. Compound showed inhibitory activity comparable to that of quercetin. Distribution analysis of compound revealed a wide presence of compound in the kingdom Fungi. These findings indicate that demethylincisterol A () is a natural antibiotic that may be used in the development of novel antibiotics against .