Our previous research found that the crude extract of Neo-T. siphonanthun exhibited an effective DPPH (1,1-diphenyl-2-picryhydrazyl) radical scavenging activity. In this study an online rapid screening method, high-performance liquid chromatography-radical scavenging detection-diode array detector-electrospray ionization mass spectrometry (HPLC-RSD- DAD-ESI/MS) system, was developed for screening individual antioxidants from the most active fraction. Accordingly, three isomeric derivatives were detected. The target active compounds were isolated by high-speed counter-current chromatography (HSCCC) with the purity over 99%, and were identified as luteolin-3'-O-β-D-glucopyranoside (1), luteolin-7-O-β-D-glucopyranoside (2) and luteolin-4'-O-β-D-glucopyranoside (3) by analysis of its off-line nuclear magnetic resonance (NMR) spectra. Antioxidant activity of three compounds was assessed by off-line DPPH assay, and all of them showed potent activity.
HPLC-RSD-DAD-ESI/MS; radical scavenger; flavonoid; HSCCC; Neo-Taraxacum siphonanthun
