Chemical characterization of small‐molecule inhibitors of monoamine oxidase B synthesized from the Acanthopanax senticosus root with affinity ultrafiltration mass spectrometry

Rationale Discovering and identifying new small‐molecule inhibitors of monoamine oxidase B (MAO‐B) could provide the potential to treat many neurodegenerative diseases. Methods We employed affinity ultrafiltration liquid chromatography/tandem mass spectrometry (AUF‐LC/MS n ) to identify and characterize small‐molecule inhibitors of MAO‐B from a 30% ethanolic extract of Acanthopanax senticosus root (ASR). In vitro tests were performed in stimulated BV2 microglia to evaluate the anti‐inflammatory effects of the ASR preparation. An in vitro enzyme activity assay, measuring half‐maximal inhibitory concentrations (IC 50 ) against MAO‐B, determined the inhibitory activity of the potential MAO‐B ligands. Results ASR treatment significantly inhibited NO release ( p <0.01) and attenuated tumor necrosis factor (TNF)‐α expression in stimulated BV2 microglia. Nine compounds were isolated from the ASR preparation as potential MAO‐B inhibitors, identified as quinic acid, chlorogenic acid, isofraxidin, dicaffeoylquinic acid, pinoresinol diglucoside, medioresinol 4’‐ O ‐β‐D‐glucopyranoside, eletutheroside E, syringaresinol O ‐β‐D‐glucoside, and trihydroxyoctadecenoic acid, based on their tandem mass spectra. Conclusions Our study provides critical data on compounds from ASR extracts which are suitable for the development of new MAO‐B inhibitors as potential therapeutics for neurodegenerative diseases.