Identification of flavone aglycones and glycosides in soybean pods by liquid chromatography–tandem mass spectrometry

High-performance liquid chromatography–atmospheric pressure chemical ionization mass spectrometry was used to identify flavone aglycones and glycosides in soybean pods. Tandem mass spectrometry (MS–MS and MS–MS–MS) and photodiode array detection were also utilized in flavone characterization. A total of seven flavone aglycones and glycosides were identified. Among them three flavone aglycones—apigenin, 7,4′-dihydroxyflavone, and luteolin—and two flavone glycosides—apigenin-7-O-β-d-glucoside, and luteolin-7-O-β-d-glucoside—were unambiguously identified based on their abundant (M+H)+ ions, UV spectra, retention time, and tandem mass spectrometric analysis compared with authentic standards. The tentative identification of two flavone glycosides as 7,4′-dihydroxyflavone-7-O-β-d-glucoside and apigenin-7-O-β-d-glucoside-6″-O-malonate was based on UV spectra, (M+H)+ ions, and tandem mass spectrometry. This is the first report identifying flavone aglycones and glycosides in soybean pods.