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

To identify the structures of flavonoid glycosides in bee pollen collected from rapeseed plants ( Brassica napus 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- O -β-D-glucosyl-(2→l)-β-glucoside, (2) kaempferol-3, 4′-di- O -β-D-glucoside, (3) 5, 7, 4′-trihydroxy-3′-methoxyflavone-3- O -β-D-sophoroside and (4) kaempferol-3- O -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.