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

Abstract

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(n) 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.

Kale: An excellent source of vitamin C, pro-vitamin A, lutein and glucosinolates

“…In recent years, kale has gained the attention of the scientific community due to its high content of bioactive compounds such as vitamin C, provitamin A, glucosinolates, phenolic antioxidants, dietary fiber, micronutrients (iron, zinc and manganese) and macronutrients (calcium and magnesium) (Ayaz et al, 2006;Cartea, Velasco, Obregón, Padilla, & de Haro, 2008;Khachik, Beecher, & Goli, 1991;Olsen, Aaby, & Borge, 2009). Likewise, in vitro and in vivo studies suggest that kale have a positive impact on the prevention of chronic diseases such as cardiovascular diseases (Kahlon, Chapman, & Smith, 2007;Kim, Yoon, Kwon, Park, & Lee-Kim, 2008;Kural, Küçük, Yücesan, & Örem, 2011) and cancer (Chung, Lee, & Sung, 2002).…”

A Comparative Study on Proximate and Antioxidant Activity of Brassica oleracea (Kale) and Spinacea oleracea (Spinach) Leaves

“…It remained at room temperature for 30 min; the absorbance of the reaction mixture was measured at 415 nm with a UV-Visible spectrophotometer. The calibration curve was prepared by preparing quercetin solutions at concentrations 12.5 to 100 mg/g in aqueous extract (Olsen et al, 2009). …”

Chemical composition and anti-biofilm activity of burdock (<i>Arctium lappa</i> L Asteraceae) leaf fractions against <i>Staphylococcus aureus</i>

“…The crude extracts (100 g) were dissolved in water, then loaded on a glass column (6 cm × 100 cm) of macroporous resin (HPD-100, Cangzhou Bon Adsorber Technology Co, Ltd, China). In the macroporous resin column chromatography, water and ethanol (20,34, and 70 %) was successively used to desorb target components at a successively flow of 1.5 BV/h, respectively. Each eluted fraction was collected and dried.…”