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

Maize hydroxycinnamic acids: unveiling their role in stress resilience and human health

Maize production is pivotal in ensuring food security, particularly in developing countries. However, the crop encounters multiple challenges stemming from climatic changes that adversely affect its yield, including biotic and abiotic stresses during production and storage. A promising strategy for enhancing maize resilience to these challenges involves modulating its hydroxycinnamic acid amides (HCAAs) content. HCAAs are secondary metabolites present in plants that are essential in developmental processes, substantially contributing to defense mechanisms against environmental stressors, pests, and pathogens, and exhibiting beneficial effects on human health. This mini-review aims to provide a comprehensive overview of HCAAs in maize, including their biosynthesis, functions, distribution, and health potential applications.

Arabinoxylan from Corn Fiber Obtained through Alkaline Extraction and Membrane Purification: Relating Bioactivities with the Phenolic Compounds

Arabinoxylan has prebiotic properties, as it is able to resist digestion in the small intestine and undergoes fermentation in the large intestine. In this work, arabinoxylan was extracted from corn fiber using an alkaline solution and further purified with membrane processing. It was found that the extracts were mainly composed of xylose (50-52%), arabinose (37-39%), galactose (9%) and glucose (1-4%), with an A/X ratio of 0.72-0.77. All the extracts were composed of phenolic compounds, including ferulic acid derivatives such as dimers, trimers and tetramers. The purified extract had a lower concentration of ferulic and p-coumaric acid (0.004 and 0.02 mg/mgdry_weight, respectively) when compared to raw extract (19.30 and 2.74 mg/mgdry_weight, respectively). The same effect was observed for the antioxidant activity, with purified extracts having a lower value (0.17 ± 0.02 µmol TEAC/mg) when compared to the raw extract (2.20 ± 0.35 µmol TEAC/mg). The purified extract showed a greater antiproliferative effect against the HT29 cell line with EC50 = 0.12 ± 0.02 mg/mL when compared to the raw extract (EC50 = 5.60 ± 1.6 mg/mL). Both raw and purified extracts did not show any cytotoxicity to the Caco-2 cell line in the maximum concentration tested (10 mg/mL).

Evaluation of Tandem Mass Spectrometry Experiments in the Negative Ionization Mode for Phenolamide Regioisomer Characterization

Phenolamides are abundant specialized metabolites found in nature and consist of hydroxycinnamic acids mono- or polyconjugated with polyamines. Their participation in flower development is well-documented, and their presence in pollen raises the question of their role in pollen/pollinator interactions. The structural characterization of phenolamides is complicated by the presence of positional isomers and stereoisomers. Liquid chromatography coupled to tandem mass spectrometry in the positive ionization mode is becoming very popular in phenolamide structural characterization. However, collision-induced transamidation processes that cause the swapping of side chains have been detected, making it difficult to distinguish regioisomers with this technique. In the present report, we explore the dissociation processes undergone by the [M - H]^- ions of spermidine-based phenolamides as model compounds. We describe two original competitive dissociation routes, namely, the phenolate and imidate pathways, to account for the observed fragmentation reactions undergone by collisional activated standard phenolamide anions. Whereas the phenolate pathway is regioselective at the central position for spermidine, the imidate pathway, requiring a deprotonated amide, only occurs at the extremities. Tandem mass spectrometry experiments on negatively charged phenolamide ions may then outperform their positive ionization mode counterparts for the distinction between phenolamide regioisomers and globally for the identification of phenolamides in natural extracts.

Nutritional and Phytochemical Composition of Mahewu (a Southern African Fermented Food Product) Derived from White and Yellow Maize (Zea mays) with Different Inocula

Mahweu is an important indigenous beverage for many low-income and undernourished consumers in southern Africa. As a result, the nutritional and phytochemical profile of mahewu samples (obtained using optimized fermentation and boiling conditions from a previous study) as well as their related raw materials (white and yellow maize) were investigated. At these conditions, white and yellow maize mahewu (WM and YM) were prepared utilizing various inocula including sorghum malt, wheat, millet malt, or maize malt, and the pH, titratable acidity (TTA), total soluble solid (TSS), and proximate analysis were determined. The mineral content, amino acid composition, and phenolic compound profile were also investigated using inductive coupled plasma optical emission spectrometry (ICP-OES), high-performance liquid chromatography (HPLC), and ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS), respectively. Fermentation was observed to have influenced the proximate composition of obtained mahewu samples compared to the raw flour with significant (p ≤ 0.05) improvement in protein from 8.59 to 9.7% (YM) and 8.78 to 9% (WM) as well as carbohydrate from 72.27 to 74.47% (YM) and 71.15 to 72.65% (WM). Sodium, magnesium, phosphorous, potassium, calcium, manganese, iron, copper, and zinc were the minerals detected in the mahewu samples, while potassium was the most abundant mineral, having values ranging from 3051.61 to 3283.38 mg/kg (YM) and 2882.11 to 3129.97 mg/kg (WM). Heavy metals detected in this study were all below the recommended tolerable levels by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Arginine and leucine with values ranging from 0.47 to 0.52 g/100 g (YM) and 0.48 to 0.53 g/100 g (WM) as well as 0.91 to 1.04 g/100 g (YM) and 0.95 to 1.01 g/100 g (WM), respectively, were the most abundant essential amino acids, whereas for non-essential amino acids, glutamic acid, aspartic acid, alanine, and proline were observed to be abundant. Based on the different inocula, the derived mahewu samples prepared using either white or yellow maize have varying nutritional and health beneficial components and the choice of inocula might still be determined by consumer preference.

Effects of bioactive molecules on the concentration of biogenic amines in foods and biological systems

Biogenic amines (BAs) are a group of molecules naturally present in foods that contain amino acids, peptides, and proteins as well as in biological systems. In foods, their concentrations typically increase during processing and storage because of exposure to microorganisms that catalyze their formation by releasing amino acid decarboxylases. The concentrations of BAs above certain values are indicative of unsafe foods due to associate neuronal toxicity, allergenic reactions, and increase risks of cardiovascular diseases. There are therefore various strategies that focus on the control of BAs in foods mostly through elimination, inactivation, or inhibition of the growth of microorganisms. Increasingly, there are works on bioactive compounds that can decrease the concentration of BAs through their antimicrobial activity as well as the inhibition of decarboxylating enzymes that control their formation in foods or amine oxidases and N-acetyltransferase that control the degradation in vivo. This review focusses on the role of food-derived bioactive compounds and the mechanism by which they regulate the concentration of BAs. The findings are that most active molecules belong to polyphenols, one of the largest groups of plant secondary metabolites, additionally other useful +compounds are present in extracts of different herbs and spices. Different mechanisms have been proposed for the effects of polyphenols depending on the model system. Studies on the effects in vivo are limited and there is a lack of bioavailability and transport data which are important to assess the importance of the bioactive molecules.

Towards a broader view of the metabolome: untargeted profiling of soluble and bound polyphenols in plants

Phenylalanine (Phe) is a central precursor for numerous secondary plant metabolites with a multitude of biological functions. Recent studies on the fungal disease Fusarium head blight in wheat showed numerous Phe-derived defence metabolites to be induced in the presence of the pathogen. These studies also suggest a partial incorporation of Phe-derived secondary metabolites into the cell wall. To broaden the view of the metabolome to bound Phe derivatives, an existing approach using ¹³C-labelled Phe as tracer was extended. The developed workflow consists of three successive extractions with an acidified acetonitrile-methanol-water mixture to remove the soluble plant metabolites, followed by cell wall hydrolysis with 4M aqueous NaOH, acidification with aqueous HCl, and liquid-liquid extraction of the hydrolysate with ethyl acetate. The untargeted screening of Phe-derived metabolites revealed 156 soluble compounds and 90 compounds in the hydrolysed samples including known cell wall constituents like ferulic acid, coumaric acid, and tricin. Forty-nine metabolites were found exclusively in the hydrolysate. The average cumulative extraction yield of the soluble metabolites was 99.6%, with a range of 91.8 to 100%. Repeatability coefficients of variation of the protocol ranged from 10.5 to 25.9%, with a median of 16.3%. To demonstrate the suitability of the proposed method for a typical metabolomics application, mock-treated and Fusarium graminearum-treated wheat samples were compared. The study revealed differences between the hydrolysates of the two sample types, confirming the differential incorporation of Phe-derived metabolites into the cell wall under infection conditions.

Four almost unexplored species of Brazilian Connarus (Connaraceae): Chemical composition by ESI-QTof-MS/MS-GNPS and a pharmacologic potential

INTRODUCTION

Species of Connaraceae are globally used in traditional medicines. However, several of these have not been studied regarding their chemical composition, and some are even at risk of extinction without proper studies. Therefore, the chemical composition and pharmacological potential of Connarus blanchetii Planch., Connarus nodosus Baker, Connarus regnellii G. Schellenb., and Connarus suberosus Planch., which were previously unknown, were analyzed.

OBJECTIVE

This work aims to investigate the pharmacological potential of these four Connarus species. The chemical composition of different extracts was determined by high-resolution mass spectrometry (HRMS), with subsequent analysis by the GNPS platform and competitive fragmentation modeling (CFM).

MATERIALS AND METHODS

Leaf extracts (C. blanchetii, C. nodosus, C. regnellii, and C. suberosus) and bark extracts (C. regnellii and C. suberosus) were obtained by decoction, infusion, and maceration. LC/HRMS data were submitted to the GNPS platform and evaluated using CFM in order to confirm the structures.

RESULTS

The HRMS-GNPS/CFM analysis indicated the presence of 23 compounds that were mainly identified as phenolic derivatives from quercetin and myricetin, of which 21 are unedited in the Connarus genus. Thus, from the analyses performed, we can identify different compounds with pharmacological potential, as well as the most suitable forms of extraction.

CONCLUSION

Using HRMS-GNPS/CFM, 21 unpublished compounds were identified in the studied species. Therefore, our combination of data analysis techniques can be used to determine their chemical composition.

Shedding Light on the Volatile Composition of Broa, a Traditional Portuguese Maize Bread

In Portugal, maize has been used for centuries to produce an ethnic bread called broa, employing traditional maize varieties, which are preferred by the consumers in detriment of commercial hybrids. In order to evaluate the maize volatiles that can influence consumers’ acceptance of broas, twelve broas were prepared from twelve maize varieties (eleven traditional and one commercial hybrid), following a traditional recipe. All maize flours and broas were analyzed by HS-SPME-GC-MS (headspace solid-phase microextraction) and broas were appraised by a consumer sensory panel. In addition, the major soluble phenolics and total carotenoids contents were quantitated in order to evaluate their influence as precursors or inhibitors of volatile compounds. Results showed that the major volatiles detected in maize flours and broas were aldehydes and alcohols, derived from lipid oxidation, and some ketones derived from carotenoids’ oxidation. Both lipid and carotenoids’ oxidation reactions appeared to be inhibited by soluble phenolics. In contrast, phenolic compounds appeared to increase browning reactions during bread making and, consequently, the production of pyranones. Traditional samples, especially those with higher contents in pyranones and lower contents in aldehydes, were preferred by the consumer sensory panel. These findings suggest that, without awareness, consumers prefer broas prepared from traditional maize flours with higher contents in health-promoting phenolic compounds, reinforcing the importance of preserving these valuable genetic resources.

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

Maize is an important source of phenolic compounds, specially hydroxycinnamic acids, which are widely known for their antioxidant activity and associated health benefits. However, these effects depend on their bioaccessibility, which is influenced by the different techniques used for food processing. Several traditional products can be obtained from maize and, in Portugal, it is used for the production of an ethnic bread called broa. In order to evaluate the effect of processing on maize phenolic composition, one commercial hybrid and five open-pollinated maize flours and broas were studied. The total phenolic content and antioxidant activity were evaluated by the Folin-Ciocalteu and ORAC assays, respectively. The major phenolics, namely ferulic and p-coumaric acids (in their soluble-free, soluble-conjugated and insoluble forms), insoluble ferulic acid dimers and soluble hydroxycinnamic acid amides were quantitated. Results show that the total phenolic content, antioxidant activity and hydroxycinnamic acids resisted traditional processing conditions used in the production of broas. The content in soluble-free phenolics increased after processing, meaning that their bioaccessibility improved. Portuguese traditional broas, produced with open-pollinated maize varieties, can be considered an interesting dietary source of antioxidant compounds due to the higher content in hydroxycinnamic acids and derivatives.