Determination of Flavonols and Flavonol Glycosides in Red Onion by Ultra High Performance Liquid Chromatography-Photodiode Array Detection-Tandem Quadrupole Mass Spectrometry / 分析化学

ABSTRACT

An ultra high performance liquid chromatography-photodiode array detection-tandem quadrupole mass spectrometry ( UPLC-PAD-MS/MS) method was developed for the determination of total 13 flavonols and flavonol glycosides in red onion which including 6 quercetin and its glycosides, 4 isorhamnetin and its glycosides, 3 Kaempferol and its glycosides. The chromatographic separation was carried out by used a UPLC HSS T3 column and eluted under gradient with mobile phases of acetonitrile and water both contained 0 . 1%formic acid at a flow rate of 0. 3 mL/min. The results showed that the major flavonols and flavonol glycosides in red onion were quercetin-4’-glucoside, quercetin-3, 4’-diglucoside, quercetin and Isorhamnetin-4’-glucoside. The amounts and distributions of flavonols and flavonol glycosides among different parts of red onion were different. For the same amount of dry materials, the content ratio of total flavonols and flavonol glycosides in the outer two layers, the third layer and the inner layer was 60. 333. 06. 7, the amount of quercitin and its glycosides accounts above 92. 1% of total flavonols and flavonol glycosides for each part. In the outer two layers, the amount of flavonol monoglycosides are the highest, in the third layer, the amount of flavonol aglycones were the highest, but in the inner layer, the amount of flavonol diglycosides were the highest. Small amounts of Kaempferol and its glycosides were found in red onion, and mostly were found in outer layers. This method is simple, fast, accurate and convenient, and can be used to analyze flavonols and flavonol glycosides in onion product.