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.
Highlights
Maize (Zea mays) is widely grown throughout the world, being considered a staple cereal in many countries, where it can be used to produce different food products [1]
To the best of our knowledge, these compounds have not been previously described, and these results provide evidence that hydroxycinnamic acid amides (HCAAs) are constituents of maize cell walls
Since it has been described that HCAAs and FA dehydrodimers exhibit higher antioxidant and anti-inflammatory activities than free FA [8,17,44], insoluble HCAAs constituted by FA dehydrodimers and trimers may exhibit interesting beneficial health effects
Summary
Maize (Zea mays) is widely grown throughout the world, being considered a staple cereal in many countries, where it can be used to produce different food products [1]. Among the phytochemicals present in cereals, phenolic compounds, namely hydroxycinnamic acids, contribute positively for human health [4,5] due to their antibacterial, anti-ageing, anti-carcinogenic, neuroprotective, cardiovascular and anti-diabetic properties [4]. In comparison to other cereals, whole maize grains contain higher levels of hydroxycinnamic acids [4]. Abundant free hydroxycinnamic acids present in maize grains are ferulic (FA) and p-coumaric (pCA) acids. These acids can be conjugated with polyamines, yielding hydroxycinnamic acid amides (HCAAs), such as N,N0 -feruloyl putrescine (DFP) [7,8,9]
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