Characterization and Quantification of Flavonoids and Hydroxycinnamic Acids in Curly Kale(Brassica oleracea L.Convar.acephala Var.sabellica)by HPLC-DAD-ESI-MS'

摘要

Kale is a leafy green vegetable belonging to the Brassicaceae family,a group of vegetables including cabbage,broccoli,cauliflower,and Brussels sprouts,with a high content of health-promoting phytochemicals.The flavonoids and hydroxycinammic acids of curly kale(Brassica oleracea L ssp.oleracea convar.acephala(DC.)Alef.var.sabellica L),a variety of kale,were characterized and identified primarily through HPLC-DAD-ESI-MS'analysis.Thirty-two phenolic compounds including glycosides of quercetin and kaempferol and derivatives of p-coumaric,ferulic,sinapic,and caffeic acid were tentatively identified,providing a more complete identification of phenolic compounds in curly kale than previously reported.Moreover,three hydroxycinnamic acids and one flavonoid with an unusual high grade of glycosylation,quercetin-3-disinapoyl-triglucoside-7-diglucoside,have been tentatively identified for the first time.The influence of different extraction conditions(extraction method,solvent type,solvent/solid ratio,and duration of extraction)was investigated.The total flavonol and hydroxycinnamic acid contents in curly kale determined as rutin equivalents(RE)were 646 and 204 mg of RE/100 g of fresh weight(fw),respectively.The contents of individual flavonoids ranged from 2 to 159 mg of RE/100 g of fw,with main compounds kaempferol-3-sinapoyl-diglucoside-7-diglucoside(18.7%)and quercetin-3-sinapoyl-diglucoside-7-diglucoside(16.5%).After acidic hydrolysis,two flavonol aglycones were identified in curly kale,quercetin and kaempferol,with total contents of 44 and 58 mg/100 g of fw,respectively.