Hydroxycinnamic Acids and Their Derivatives in Broa, a Traditional Ethnic Maize Bread

Abstract

Maize is one of the most interesting dietary sources of hydroxycinnamic acids, widely known for their beneficial health effects, namely antioxidant properties. This work aims to identify hydroxycinnamic acids and their derivatives in broa, a Portuguese traditional ethnic maize bread, and corresponding maize flours. Soluble and insoluble phenolic fractions of diverse maize flours and corresponding broas were prepared and analysed by HPLC-DAD-MS/MS (high-performance liquid chromatography coupled with diode array detector and tandem mass spectrometry). Besides free hydroxycinnamic acids, mainly ferulic and p-coumaric acids, several structural isomers and stereoisomers of insoluble ferulic acid dehydrodimers (n = 18) and trimers (n = 11), were also identified. Hydroxycinnamic acid amides consisting of coumaroyl and feruloyl conjugates (n = 22) were present in both soluble and insoluble fractions of maize flours and breads, in different isomeric forms. A new compound was putatively identified as bis-N,N′-diferuloyl putrescine. Additionally, more complex and insoluble hydroxycinnamic acid amides, derived from ferulic acid dehydrodimers (n = 47) and trimers (n = 18), were also putatively identified for the first time, suggesting that hydroxycinnamic acid amides are also linked to maize cell walls. Since hydroxycinnamic derivatives were not only identified in maize flours, but also in broas, they can contribute to the antioxidant properties and beneficial health effects of maize-based foods.

Broa, an Ethnic Maize Bread, as a Source of Phenolic Compounds

“…The reagents and commercial standards used for chromatographic analysis were described elsewhere [ 11 ]. Additionally, Folin-Ciocalteu reagent, sodium carbonate, 2′,2′-azobis-(2-amidinopropane) dihydrochloride (AAPH), Trolox and fluorescein sodium salt were obtained from Sigma-Aldrich, St. Louis, MO, USA.…”

“…Cereal flours (maize, rye and wheat) and broas (4 g) were submitted to a conventional extraction procedure [ 11 ] with 20 mL of EtOH/H 2 O (50%, v/v ), to obtain an ethanolic solution containing the soluble phenolic compounds and a solid residue comprising the insoluble compounds. Alkaline hydrolyses were applied to both the ethanolic solution and residue.…”

“…Phenolic compounds were analyzed in a Thermo Fisher Scientific (Waltham, MS, USA) Surveyor high-performance liquid chromatography (HPLC) system, equipped with a diode array detector (DAD) programmed for scanning between 192 and 798 nm and an electrochemical detector, ED 40 Dionex (Sunnyvale, CA, USA). Analytical conditions for HPLC-DAD were previously reported [ 11 ]. In order to detect the phenolic compounds that could exhibit AA, electrochemical detection was programmed for a linear variation from −1.0 to 1.0 V in 1.00 s (detection by integrated voltammetry using a cyclic variation of the potential).…”

“…Soluble phenolic compounds can be present in their free form or conjugated with smaller molecules, such as simple sugars and amines, as hydroxycinnamic acid amides [ 5 , 6 , 7 , 8 , 9 ]. Insoluble phenolic compounds are mostly (>94%) bound to arabinoxylans [ 4 , 5 , 10 ], and include dehydrodiferulic, dehydrotriferulic and dehydrotetraferulic acids [ 4 , 5 ] and their derivatives, such as the recently described insoluble hydroxycinnamic acid amides [ 11 ].…”

“…Conversely, insoluble compounds have a very low bioaccessibility [ 4 , 13 ] and need to be liberated from the food matrix during small intestinal digestion or colonic fermentation, in order to be absorbed and become bioavailable [ 12 ]. In a previous study, several phenolic compounds, mainly hydroxycinnamic acids and hydroxycinnamic acid amides, were identified in maize flours and broas [ 11 ].…”