Characterization of inhibitory constituents of NO production from Catalpa ovata using LC-MS coupled with a cell-based assay

An effective screening method for inhibitors of NO production in natural products using LC-QTOF MS/MS coupled with a cell-based assay was proposed. The ethyl acetate fraction of Catalpa ovata exhibited a strong inhibitory effect on NO production in lipopolysaccharide-induced BV2 microglia cells. We attempted to identify the active constituents of C. ovata by using LC-QTOF MS/MS coupled with a cell-based assay. Peaks at approximately 14–15 min on the MS chromatogram were estimated to be the bioactive constituents. A new iridoid compound, 6-O-trans-feruloyl-3β-hydroxy-7-deoxyrehamaglutin A (4), and nine known compounds (1–3, 5–10) were isolated from the ethyl acetate fraction of C. ovata by repeated column chromatography. Compounds 3, 4, 5, 7, and 8 significantly attenuated lipopolysaccharide-stimulated NO production in BV2 cells. Our results indicate that LC-QTOF MS/MS coupled with a cell-based NO production inhibitory assay successfully predicted active compounds without a time-consuming isolation process.