Metabolomic analysis of the polyphenols in germinating mung beans (Vigna radiata) seeds and sprouts.

Background: The mung bean (Vigna radiata) is a key food crop in much of Asia and contains plentiful biological activities to prevent human disease. Mung bean sprouts have more plentiful metabolites and activities after germination.

Results: The metabolite profile of polyphenols in the germination process was described using the methods of ultra-high-performance liquid chromatography coupled with time-of-flight mass spectrometry and partial least squares discriminant analysis. Sprouts from different periods were clearly discriminated from each other. Eight flavonoids - vitexin, isovitexin, rutin, kaempferol 3-O-rutinoside, isoquercitrin, genistein, daidzein and isorhamnetin - and two phenolic acids - shikimic acid and caffeic acid - were thought to be chemical markers of the sprouts. The method of high-performance liquid chromatography with diode array detection was established to quantitatively analyze the eight chemical markers of flavonoids, and provides good linearity, repeatability, intra- and inter-day precision, accuracy and recovery. The main metabolic and transformation pathways of the polyphenols in the germination process were discussed.

Conclusion: The proposed method is sensitive, rapid and robust. Understanding the complete profile of polyphenol metabolites in the germination process may be useful for better utilizing mung beans sprouts as the raw materials of functional food, health products and cosmetics.