Abstract
Black carrot has been attracting increasing thanks to its high bioactive compound content. This study presents the polyphenol bio-accessibility of black carrot and two derived products (black carrot snack (BC snack) and black carrot seasoning (BC seasoning)) after in vitro gastrointestinal digestion and colonic fermentation. Additionally, antioxidant activity was measured by 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) assays. Nine flavonoids and eight anthocyanins were determined by ultra high-performance liquid chromatography high resolution mass spectrometry (UHPLC-HRMS) analysis, the predominant compounds being the hydroxycinnamic acids 3-O-feruloylquinic acid, 4-O-feruloylquinic acid and chlorogenic acid. The BC snack (108 µmol/g DW) presented the highest total polyphenol content, followed by BC seasoning (53 µmol/g DW) and black carrot (11.4 µmol/g DW). The main polyphenols still bio-accessible after in vitro digestion were the hydroxycinnamic acids, with mean recovery rates of 113 % for black carrot, 69% for BC snack and 81% for BC seasoning. The incubation of black carrot and its derived products with human faecal bacterial resulted in the complete degradation of anthocyanins and in the formation of mainly 3-(4′-hydroxyphenyl)propanoic acid as the major catabolic event. In conclusion, our results suggest that the black carrot matrix impacts significantly affects the bio-accessibility of polyphenols and, therefore, their potential health benefits.
Highlights
HPLC-grade methanol (MeOH), acetone and potassium hydroxide were acquired from Panreac Applichem ITW Reagents (Darmstadt, Germany); sodium chloride and magnesium chloride hexahydrate were purchased from Fisher Scientific (Madrid, Spain); 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), fluorescein, 2,20 -azobis(2amidinopropane)dihydrochloride (AAPH), 2,20 -azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), sodium bicarbonate and ammonium carbonate were supplied by Sigma-Aldrich (Madrid, Spain); and potassium dihydrogen phosphate, sodium hydrogen carbonate, magnesium sulfate monohydrate and potassium hydrogen phosphate were obtained from VWR International Eurolab (Barcelona, Spain)
A total of 21 polyphenols were identified in black carrot and its derived products, including four hydroxybenzoic acids, seven hydroxycinnamic acids, two flavonols and eight anthocyanins
Hydroxycinnamic acid derivatives such as chorogenic acid (2.52 μmol/g DW), 3-O-feruoylquinic acid (4.01 μmol/g DW) and p-coumaroylquinic acid (4.41 μmol/g DW) were the main polyphenols determined in black carrot, representing 95.8 % of the total polyphenol content, which is in accordance with previously published data [1,7]
Summary
Orange carrots are more common, the consumption of black carrots is currently increasing in Western Europe due to their benefits in human health. They present antioxidant, anti-proliferative and anti-inflammatory properties [2,3], which have been associated with their content of bioactive compounds, which are significantly related to antioxidant capacity [4,5,6]. Black carrot is characterized by an intense purple colour, which is attributed to its unique profile in specific water-soluble pigments, namely anthocyanins. Black carrots contain significant amounts of phenolic acids, including caffeoylquinic, chlorogenic, caffeic, sinapic, ferulic and coumaric acids [7,13,14,15]
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