Characterization of flavonoid glycosides from rapeseed bee pollen using a combination of chromatography, spectrometry and nuclear magnetic resonance with a step-wise separation strategy

<div><p>To identify the structures of flavonoid glycosides in bee pollen collected from rapeseed plants (<i>Brassica napus</i> L.), we utilised an approach that combined liquid chromatography–diode array detector–electrospray ionization–mass spectrometry (LC–DAD–ESI–MS) and nuclear magnetic resonance (NMR) technology with a step-wise separation strategy. We identified four constituents of high purity in rape bee pollen samples: (1) quercetin-3-<i>O</i>-β-D-glucosyl-(2→l)-β-glucoside, (2) kaempferol-3, 4′-di-<i>O</i>-β-D-glucoside, (3) 5, 7, 4′-trihydroxy-3′-methoxyflavone-3-<i>O</i>-β-D-sophoroside and (4) kaempferol-3-<i>O</i>-β-D-glucosyl-(2→l)-β-D-glucoside. This study will also provide useful reference standards for qualification and quantification of four flavonoid glycosides in natural products.</p>