Structural profile of soluble and bound phenolic compounds in teff (Eragrostis tef) reveals abundance of distinctly different flavones in white and brown varieties

Mechanisms of flavonoid inhibition of Maillard reaction product formation in relation to whole grains processing

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low Mw MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33-86%) and Mw (3.5-15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products.

From 'Farm to Fork': Exploring the Potential of Nutrient-Rich and Stress-Resilient Emergent Crops for Sustainable and Healthy Food in the Mediterranean Region in the Face of Climate Change Challenges

In the dynamic landscape of agriculture and food science, incorporating emergent crops appears as a pioneering solution for diversifying agriculture, unlocking possibilities for sustainable cultivation and nutritional bolstering food security, and creating economic prospects amid evolving environmental and market conditions with positive impacts on human health. This review explores the potential of utilizing emergent crops in Mediterranean environments under current climate scenarios, emphasizing the manifold benefits of agricultural and food system diversification and assessing the impact of environmental factors on their quality and consumer health. Through a deep exploration of the resilience, nutritional value, and health impacts of neglected and underutilized species (NUS) such as quinoa, amaranth, chia, moringa, buckwheat, millet, teff, hemp, or desert truffles, their capacity to thrive in the changing Mediterranean climate is highlighted, offering novel opportunities for agriculture and functional food development. By analysing how promoting agricultural diversification can enhance food system adaptability to evolving environmental conditions, fostering sustainability and resilience, we discuss recent findings that underscore the main benefits and limitations of these crops from agricultural, food science, and health perspectives, all crucial for responsible and sustainable adoption. Thus, by using a sustainable and holistic approach, this revision analyses how the integration of NUS crops into Mediterranean agrifood systems can enhance agriculture resilience and food quality addressing environmental, nutritional, biomedical, economic, and cultural dimensions, thereby mitigating the risks associated with monoculture practices and bolstering local economies and livelihoods under new climate scenarios.

The role of omics in improving the orphan crop tef

Tef or teff [Eragrostis tef (Zucc.) Trotter] is a cereal crop indigenous to the Horn of Africa, where it is a staple food for a large population. The popularity of tef arises from its resilience to environmental stresses and its nutritional value. For many years, tef has been considered an orphan crop, but recent research initiatives from across the globe are helping to unravel its undisclosed potential. Advanced omics tools and techniques have been directed toward the exploration of tef's diversity with the aim of increasing its productivity. In this review, we report on the most recent advances in tef omics that brought the crop into the spotlight of international research.

Phytochemical Profiling by UPLC-ESI-QTOF-MS of Kalaharia uncinata (Schinz) Moldenke, Widely Used in Traditional Medicine in DR Congo

Kalaharia uncinata (Schinz) Moldenke, is a tropical erect bushy shrub or subshrub of the Lamiaceae family. It is an endemic plant species of Southern Africa, widely used in the pharmacopoeia against upper respiratory tract infections. A previously conducted ethnobotanical survey revealed that it is believed to contain bioactive substances. However, no relevant phytochemical information was available. This study aimed to perform a phytochemical characterization of K. uncinata and also to discuss the potential bioactivity of the identified phytochemical constituents based on documented data. Ultra-performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS) was used for profiling and identification of the main phytochemical constituents from leaf extracts (MeOH 90 %, DCM, AcOEt, BuOH, hexane and residue) of K.uncinata. Twenty-four constituents, representing mainly flavonoids (14), followed by phenylethanoid glycosides (7), phenolic acids (2), and an iridoid glycoside (1) were tentatively identified. Most of the identified compounds are documented to have antiviral and anti-inflammatory properties, which could possibly be the rationale behind the use of K. uncinata against upper respiratory tract infections.

Evaluating the Antioxidant Properties of the Ancient-Crop Tef (Eragrostis tef) Grain Extracts in THP-1 Monocytes

Tef (Eragrostis tef) is an orphan crop that is widely grown in East Africa, primarily in Ethiopia as a staple crop. It is becoming popular in the Western world owing to its nutritious and gluten-free grains and the forage quality of its biomass. Tef is also considered to have a high antioxidant capacity based on cell-free studies. However, the antioxidant activity of tef has never been validated using a physiologically relevant cell model. The purpose of this study was to investigate the antioxidant capacity of tef grain extracts using a mammalian cell model. We hypothesized that the tef grain extracts are capable of modulating the cellular antioxidant response via the modulation of glutathione (GSH) biosynthetic pathways. Therefore, we evaluated the antioxidant activity of purified tef grain extracts in the human acute monocytic leukemia (THP-1) cell line. Our findings revealed that the organic fraction of grain extracts increased the cellular GSH level, which was more evident for brown-colored tef than the ivory variety. Moreover, a brown-tef fraction increased the expressions of GSH-pathway genes, including γ-glutamate cysteine ligase catalytic (GCLC) and modifier (GCLM) subunits and glutathione reductase (GR), an enzyme that plays a key role in GSH biosynthesis, suggesting that tef extracts may modulate GSH metabolism. Several compounds were uniquely identified via mass spectrometry (MS) in GSH-modulating brown-tef samples, including 4-oxo-β-apo-13-carotenone, γ-linolenic acid (methyl ester), 4,4'-(2,3-dimethyl-1,4-butanediyl)bis-phenol (also referred to as 8,8'-lignan-4,4'-diol), and (3β)-3-[[2-[4-(Acetylamino)phenoxy]acetyl]oxy]olean-12-en-28-oic acid. Tef possesses antioxidant activity due to the presence of phytochemicals that can act as direct antioxidants, as well as modulators of antioxidant-response genes, indicating its potential role in alleviating diseases triggered by oxidative stresses. To the best of our knowledge, this is the first report revealing the antioxidant ability of tef extracts in a physiologically relevant human cell model.

Mineral, Nutritional, and Phytochemical Composition and Baking Properties of Teff and Watermelon Seed Flours

Demonstrated limitations in the mineral and nutritional composition of refined flours have led to calls for the possibility of enriching them with health-promoting supplements, such as high-value non-cereal seeds. Teff and watermelon seeds have been found suitable for the production of gluten-free flour, but so far, their potential to enrich conventional baking flours has not been comprehensively studied. Hence, the present study aimed at farinographic evaluation of dough based on refined wheat flour with additions of whole white teff (TF) and watermelon seed (WSF) and pomace (DWSF) flours (tested levels 10%, 20%, and 30%), as well as possibly extensive chemical characterization of the plant material tested, including LC-MS/MS, GC-MS, total phenolics, flavonoids, melatonin, and antioxidant potential. Most of the rheological traits were improved in the flour mixtures compared to the base white flour: development time and quality number (above 1.6-fold increase), softening and stability time (up to 1.3-fold change), and water absorption (up to 6%). Overall, the best results were achieved after the addition of watermelon seed pomace. The DWSF material was characterized by the highest levels of P, Mg, Na (7.5, 1.7, 0.4 g/kg, respectively), and Fe and Zn (124 and 27 mg/kg), while TF was the richest in Ca (0.9 g/kg) and Mn (43 mg/kg). Protein and fat levels were significantly higher in watermelon seeds compared to teff (about double and up to 10-fold, respectively). Phytochemical analyses highlighted the abundance of phenolics, especially flavones, in TF, WSF and DWSF flours (244, 93, and 721 mg/kg, respectively). However, the value of total polyphenols was low in all materials (<2 mg GAE/g), which also correlates with the low antioxidant potential of the samples. Watermelon seed pomace was characterized by significantly higher melatonin concentration (60 µg/kg) than teff (3.5 µg/kg). This study provides new information on the chemical composition and application opportunities of teff and watermelon seeds.

Polyphenol and flavonoid content in major Teff [Eragrostis tef (Zuccagni) Trotter] varieties in Amhara Region, Ethiopia

Teff [Eragrostis tef (Zuccagni) Trotter] is a small-sized cereal grain and an indigenous crop in Ethiopia. The Amhara region is one of the major teff producers regions in the country. However, information on the phenolic content of the region’s teff varieties is limited. Seventy-two teff samples were collected from three administrative zones (West Gojjam zone, Awi zone, and East Gojjam zone) of the Amhara region of Ethiopia. The samples’ total polyphenol and flavonoid contents were determined using colorimetric methods. The total flavonoid contents expressed as catechin equivalent, CE (i.e., under alkaline conditions) and quercetin equivalent, Q.E (i.e., under the methanolic solution of AlCl₃) were found to be in the range of 7.66 ± 0.60–57.36 ± 3.87 mg C.E and 15.45 ± 0.15–113.12 ± 3.09 mg Q.E per 100 g of teff samples, respectively. The corresponding total polyphenol content (TPC), described as gallic acid equivalent (G.A.E.), was in the range of 46.21 ± 1.20–133.32 ± 5.44 mg G.A.E. The results showed that the mean TPC value of the teff samples from the West Gojjam zone was enriched with polyphenol than samples from the Awi zone and East Gojjam. Furthermore, it was noted that the mean TPC and TFC values did not vary significantly between samples of the East Gojjam and Awi zone (p > 0.05). In contrast, a significant difference in mean TPC and TFC-Q.E were noted between the sampling zone of East Gojjam and West Gojjam and between West Gojjam and Awi zones (p < 0.05). These significant variations in TPC and TFC might be due to observable variations in the agroecological zones and the genetic—make-up of the samples. Person correlation indicated a significant positive correlation matrix between the three variables (p = 0.01). The teff samples were trying to be classified based on their geographical origin using hierarchical cluster analysis (HCA) and biplots. Accordingly, the variance explained by component 1 (PC1) is 67.2%, and the variance explained by component 2 (PC2) is 20.0%.

Effect of radiation processing on phenolic antioxidants in cereal and legume seeds: A review

Phenolic compounds in cereal and legume seeds show numerous benefits to human health mainly because of their good antioxidant capacity. However, long-term storage and some improper preservation may reduce their antioxidant potential. It is necessary to retain or modify the phenolic antioxidants with improved technology before consumption. Radiation processing is usually applied as a physical method to extend the shelf life and retain the quality of plant produce. However, the effect of radiation processing on phenolic antioxidants in cereal and legume seeds is still not well understood. This review summarizes recent research on the effect of radiation, including ionizing and nonionizing radiation on the content and profile of phenolic compounds, and antioxidant activities in cereal and legume seeds, the influencing factors and possible mechanisms are also discussed. The article will improve the understanding of radiation effect on phenolic antioxidants, and promote the radiation modification of natural phenolic compounds in cereal and legume seeds and other sources.

New insights into non-extractable phenolic compounds analysis

Most of the studies regarding phenolic compounds (PC) have been focused only on one fraction of PC, named extractable phenolic compounds (EPC). As the name suggests, EPC can be directly extracted from the food matrix by using an appropriate solvent. Otherwise, non-extractable phenolic compounds (NEPC) remain in the food matrix after the conventional extraction, and their analysis depends on a hydrolysis process. NEPC is a relevant fraction of PC that acts in the colon, where they are extensively fermented by the action of the microbiota. To understand the health effects associated with the NEPC intake, it is necessary to know which types of compounds are present and their content in foods. In this review, 182 studies published in the last five years about NEPC in foods were evaluated, focusing on critical points of the NEPC analysis. First, EPC exhaustive extraction should be performed before the hydrolysis processes to avoid overestimation of the NEPC fraction. NEPC hydrolysis by aggressive methods modifies their original structure and makes their complete elucidation difficult. These methods must be optimized considering the research objective, as different conditions may result in different amounts and profiles of compounds. Concerning quantification, the widely used spectrophotometric Folin-Ciocalteu method should be avoided as it leads to overestimation. Liquid chromatography coupled to a diode array detector is the most appropriate technique for this purpose. Although pure standard compounds are unavailable in most cases, standards representative of a PC family can be used, and results can be expressed as equivalent. The best approach for NEPC identification is liquid chromatography coupled to a diode array detector and tandem high-resolution mass spectrometry, which generates information regarding chromatographic behavior, UV-vis absorption, accuracy mass and fragmentation pattern. The identification process should associate manual data handling with the bioinformatics-assisted approach.

Elucidating drought responsive networks in tef (Eragrostis tef) using phenomic and metabolomic approaches

Drought is a major abiotic stress that limits crop productivity and is driving the need to introduce new tolerant crops with better economic yield. Tef (Eragrostis tef) is a neglected (orphan) Ethiopian warm-season annual gluten-free cereal with high nutritional and health benefits. Further, tef is resilient to environmental challenges such as drought, but the adaptive mechanisms remain poorly understood. In this study, metabolic changes associated with drought response in 11 tef accessions were identified using phenomic and metabolomic approaches under controlled conditions. Computerized image analysis of droughted plants indicated reductions in leaf area and green pigments compared with controls. Metabolite profiling based on flow-infusion electrospray-high-resolution mass spectroscopy (FIE-HRMS) showed drought associated changes in flavonoid, phenylpropanoid biosynthesis, sugar metabolism, valine, leucine and isoleucine biosynthesis, and pentose phosphate pathways. Flavonoid associated metabolites and TCA intermediates were lower in the drought group, whereas most of the stress-responsive amino acids and sugars were elevated. Interestingly, after drought treatment, one accession Enatite (Ent) exhibited a significantly higher plant area than the others, and greater accumulation of flavonoids, amino acids (serine and glycine), sugars (ribose, myo-inositol), and fatty acids. The increased accumulation of these metabolites could explain the increased tolerance to drought in Ent compared with other accessions. This is the first time a non-targeted metabolomics approach has been applied in tef, and our results provide a framework for a better understanding of the tef metabolome during drought stress that will help to identify traits to improve this understudied potential crop.

Kinetics of Phenolic Compounds Modification during Maize Flour Fermentation

This study aimed to investigate the kinetics of phenolic compound modification during the fermentation of maize flour at different times. Maize was spontaneously fermented into sourdough at varying times (24, 48, 72, 96, and 120 h) and, at each point, the pH, titratable acidity (TTA), total soluble solids (TSS), phenolic compounds (flavonoids such as apigenin, kaempferol, luteolin, quercetin, and taxifolin) and phenolic acids (caffeic, gallic, ferulic, p-coumaric, sinapic, and vanillic acids) were investigated. Three kinetic models (zero-, first-, and second-order equations) were used to determine the kinetics of phenolic modification during the fermentation. Results obtained showed that fermentation significantly reduced pH, with a corresponding increase in TTA and TSS. All the investigated flavonoids were significantly reduced after fermentation, while phenolic acids gradually increased during fermentation. Among the kinetic models adopted, first-order (R² = 0.45–0.96) and zero-order (R² = 0.20–0.82) equations best described the time-dependent modifications of free and bound flavonoids, respectively. On the other hand, first-order (R² = 0.46–0.69) and second-order (R² = 0.005–0.28) equations were best suited to explain the degradation of bound and free phenolic acids, respectively. This study shows that the modification of phenolic compounds during fermentation is compound-specific and that their rates of change may be largely dependent on their forms of existence in the fermented products.

Changes in metabolites with harvest times of seedlings of various Korean oat (Avena sativa L.) cultivars and their neuraminidase inhibitory effects

Oats and their seeds, stems, and leaves are approved for use as safe food ingredients. Oat seedlings are environmentally friendly and are becoming increasingly popular as they provide several health benefits. We used the UPLC-CAD to quantitatively analyze isolated compounds (1-11) between 15 cultivars of oat seedlings and their harvest time. Maximum average amount of total contents of isolated compounds was observed after the harvest time of 5 days (4711.3 mg/100 g), while the minimum was observed after the harvest time of 7 days (4184.8 mg/100 g). We demonstrated that all isolated compounds (1-11) showed neuraminidase inhibitory effects, with 6 and 7 being the most active with IC₅₀ values of 3.7 and 20.5 µM, respectively. High content of compounds 6 and 7 was observed (2306.6 mg/100 g) in the Dahan cultivar at 9 days, indicating potential good cultivars with a high content of active compounds and neuraminidase inhibition activity.

Effect of tannins on microwave-assisted extractability and color properties of sorghum 3-deoxyanthocyanins

Sorghum derived 3-deoxyanthocyanins (3-DXA) are of growing interest as natural food colors due to their unique stability compared to anthocyanins, but are generally difficult to extract. Microwave-assisted extraction (MAE) can dramatically improve extraction efficiency of 3-DXA from sorghum tissue. However, condensed tannins common in some sorghums could impact MAE extractability and color properties of 3-DXA. The objective of this work was to determine how presence of condensed tannins affect MAE extractability, stability, and color properties of sorghum 3-DXA. Sorghums of varying 3-DXA profile and tannin content, as well as purified tannins, were subjected to MAE and pigment yield and profile, aqueous color properties and stability at pH 1 - 5 monitored over time using, UV-vis spectroscopy, colorimetry, and UPLC-MS. The relative yield of 3-DXA from tannin sorghums was higher (3 - 10-fold) after MAE than from non-tannin sorghum (2-fold). During MAE, condensed tannins underwent extensive oxidative depolymerization to anthocyanidins (cyanidin and 7-O-methylcyanidin), which caused the tannin-sorghum pigment extracts to have a redder hue (12-43H°) compared to the non-tannin pigment extract (58H°). The tannin-derived anthocyanidins transformed over time into xanthylium pigments, resulting in increased extract H°. Tannins enhanced both color intensity (pH 1) and stability (pH 3-5) of the 3-DXA over 14 days, indicating they acted as copigments. The presence of tannins in sorghum enhances MAE extractability of 3-DXA from sorghum tissue, and could also potentially enhance their functionality in aqueous food systems. However, the initial changes in extract hue properties due to tannin-derived anthocyanidins should be considered.

Changes in extractable phenolic profile during natural fermentation of wheat, sorghum and teff

Whole grain polyphenols are associated with structure-specific bioactive properties. However, the phenolic profile of grain ingredients can be significantly altered by processes like fermentation. This study investigated how polyphenol profiles in different cereal grains respond to microbial metabolism during sourdough fermentation. Whole grain wheat (white and red), sorghum (white and lemon-yellow), and teff (white and brown) flours were subjected to natural sourdough fermentation for 48-96 h, and phenolic profiles and their metabolites monitored using UPLC-tandem quadrupole MS. Flavonoid O-glycosides (dominant in sorghum) were rapidly metabolized (66% reduction in 48 h) to release aglycones (2.5 fold increase). O-Glycoside groups in mixed O/C-glycosides (dominant in teff) were selectively hydrolyzed, but more slowly (11-32% reduction in 48 h) than homo-O-glycosides, suggesting steric hindrance from the C-glycoside groups. Flavonoid C-glycosides (dominant in wheat) and aglycones (white sorghum) were generally stable to microbial degradation. Extractable phenolic acids and their esters (most abundant in white sorghum) were extensively degraded (80% reduction in 48 h) with few metabolites detected at the end of fermentation. Thus, extractable phenolics in sorghum were generally most extensively metabolized, whereas those in wheat were the least impacted by sourdough fermentation. New microbial metabolites, putatively identified as O-methylcatechol-vinyl-isoflavans, were detected in all fermented samples, with levels increasing with fermentation time. Based on structure, these compounds were likely derived from cell wall C-C linked diferulic acid metabolism. As expected, Folin reactive phenols and antioxidant capacity increased in fermented samples, but the extent was distinctly smaller in sorghums (1.3-1.9 fold) vs teff (2.4-3.2 fold) and wheat (2.0-6.1 fold), likely due to higher presence of easily metabolizable phenolics in sorghum. The phenolic profile of a cereal grain affects the products of microbial metabolism during fermentation, and may thus alter phenolic-dependent bioactive properties associated with a specific grain.

1H NMR-based metabolomics and UHPLC-ESI-MS/MS for the investigation of bioactive compounds from Lupinus albus fractions

Lupinus albus or white lupine has recently received increase attention for its medicinal values. Several studies have described the hypoglycemic effect of the white lupine, which is known as a food plant with potential value for treatment of diabetes. This study provides useful information for the identification and quantification of compounds in L. albus fractions by proton nuclear magnetic resonance (¹H NMR) spectroscopy. In total, 35 metabolites were identified from L. albus fractions.Principal component analysis (PCA) was used as a multivariate projection method for visualizing the different composition of four different fractions. The bioactivities of fractions with different polarity obtained from the extract of L. albus seeds are reported. Among the fractions studied, the chloroform fraction (CF) exhibits a high free radical scavenging (DPPH) and α-glucosidase inhibitory activities with IC₅₀ values of 24.08 and 20.08 μg/mL, respectively. A partial least-squares analyses (PLS) model had been successfully performed to correlate the potential active metabolites with the corresponding biological activities. Metabolites containing proline, caprate, asparagine, lupinoisolone C, hydroxyiso lupalbigenin and some unknown compounds show high correlation with the bioactivities studied. Moreover, the structural identification in the active fraction was supported by ultrahigh-performance-liquid chromatography-electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) analysis. A total of 21 metabolites were tentatively identified from MS/MS data by comparison with previously reported data. Most of these compounds are isoflavonoids without known biological activity. This information may be useful for developing functional food from L. albus with potential application in the management of diabetes.

Application of a novel microwave energy treatment on brewers' spent grain (BSG): Effect on its functionality and chemical characteristics

The effect of a new microwave energy treatment on brewers' spent grain (BSG) functionality and its application in a bakery product was evaluated. The physicochemical modifications of BSG were studied with special emphasis on the analysis of non-enzymatic browning reactions. Microwave treatment induced the formation of Maillard reaction products with a high antioxidant activity. The structure of these compounds was fully analyzed and it was concluded that melanoidins were formed by polymerization of furanose rings. Results indicated that chlorogenic acids were also reactants involved in the development of this reaction, leading to the formation of new bioaccesible compounds with important antioxidant activity. Although the addition of BSG in cookie formulations negatively affect their texture, this effect was successfully reduced when the microwave treatment was applied on BSG. This was associated to the disrupting effect that the microwaves had on BSG fiber, which significantly reduced its water absorption index (p ≤ 0.05).

Detection of flavone C-glycosides in the extracts from the bark of Prunus avium L. and Prunus cerasus L

The extracts from the bark of Prunus avium and Prunus cerasus have been analyzed by using high pressure liquid chromatography/electrospray ionization mass spectrometry. For the first time in the bark of Prunus species flavonoid C-glycosides have been detected. On the basis of the characteristic fragmentation patterns of their [M-H]^- and [M + H]⁺ ions, three flavonoid C-glycosides have been identified, namely apigenin-6,8-di-C-glucoside (vicenin-2), apigenin-6-C-glucoside (isovitexin) and chrysin-8-C-glucoside. Taking into account the widely studied biological activities of flavonoid C-glycosides, the barks of these common fruit trees seem to be interesting materials of potential medical or cosmetic application.

Nutritional Composition and Health Benefits of Teff (Eragrostis tef (Zucc.) Trotter)

Teff (Eragrostis tef (Zucc.) Trotter) (Poaceae) is an annual crop with a very tiny grain. The crop is mainly cultivated in Ethiopia and Eritrea where it is used in preparing a pancake-like staple food called injera. Teff grain is the smallest of all whole flour grains in the world with a length of about 1.0 mm and a width of about 0.60 mm. The popularity of the crop is rapidly increasing throughout the world because of its attractive nutritional and functional properties. Thus, the crop is being successfully introduced and cultivated in many parts of the world including the USA, Canada, Australia, Switzerland, and the Netherlands. The growing global demand for the grain is due to its gluten-free nature, high level of essential amino acids (EAA), high mineral content, low glycemic index (GI), high crude fiber content, longer shelf life, and slow staling of its bread products compared to that of wheat, sorghum, rice, barley, and maize. The grain is linked to several health benefits including prevention and treatment of diseases such as celiac disease, diabetes, and anemia. These call for huge research opportunities to explore the nutritional and functional properties of the grain.

Effects of Fungi-Mediated Solid-State Fermentation on Phenolic Contents and Antioxidant Activity of Brown and White Teff (Eragrostis tef (Zucc.) Trotter) Grains

Teff (Eragrostis tef (Zucc.) Trotter) is a tropical cereal used in preparing a staple food in Ethiopia and Eritrea called injera. Phenolic compounds are available in soluble and bound forms in cereals like teff. Therefore, their bioaccessibility depends on their release from the food matrix. Different food processing methods including fermentation have been applied since ancient times to aid bioaccessibility and improve the properties of food products. This study aimed at investigating changes in phenolic profiles and antioxidant activities of white and brown teff grains during mushroom-mediated solid-state fermentation. Fermentation with mushroom considerably increased total phenol contents of the soluble phenol fraction with Ganoderma lucidum showing relatively higher increase than Pleurotus ostreatus. Bound fraction of teff phenol did not show noticeable changes after fermentation with the two mushroom strains. Such changes are suggested to be attributed to activities of fungal enzymes such as amylases, xylanases, and proteases that induce structural breakdown of grain components including cell walls leading to the liberation or synthesis of a variety of phenolic compounds. On the other hand, total flavonoid content of teff significantly decreased after fermentation by both strains. This is also believed to be caused by the action of fungal polyphenol oxidases that catalyze the oxidation of a variety of phenolic compounds including flavonoids to o-quinones.

Nitrogen availability and genotype affect major nutritional quality parameters of tef grain grown under irrigation

Worldwide demand for tef (Eragrostis tef) as a functional food for human consumption is increasing, thanks to its nutritional benefits and gluten-free properties. As a result, tef in now grown outside its native environment in Ethiopia and thus information is required regarding plant nutrition demands in these areas, as well as resulting grain health-related composition. In the current work, two tef genotypes were grown in Israel under irrigation in two platforms, plots in the field and pots in a greenhouse, with four and five nitrogen treatments, respectively. Nutritional and health-related quality traits were analyzed, including mineral content, fatty acid composition, hydrophilic and lipophilic antioxidative capacity, total phenolic content and basic polyphenolic profile. Our results show that tef genotypes differ in their nutritional composition, e.g. higher phenolic contents in the brown compared to the white genotype. Additionally, nitrogen availability positively affected grain fatty acid composition and iron levels in both experiments, while negatively affecting total phenolics in the field trials. To conclude, nitrogen fertilization is crucial for crop growth and productivity, however it also implicates nutritional value of the grains as food. These effects should be considered when fertilizing tef with nitrogen, to optimize both crop productivity and nutritional effects.

Stability of 3-deoxyanthocyanin pigment structure relative to anthocyanins from grains under microwave assisted extraction

Sorghum derived 3-deoxyanthocyanin (DXA) pigments are stable relative to their anthocyanin analogs, and are of growing interest in food applications. However, the 3DXA are poorly extractable from grain tissue. This work aimed to determine the relative stability and extractability of sorghum 3-DXA vs anthocyanins from maize and cowpea under microwave-assisted extraction (MAE). UV-Vis and UPLC-MS/MS spectrometry were used to characterize the properties. The 3-DXA remained structurally stable to MAE conditions up to 1200 W/100 °C/30 min. MAE increased sorghum 3-DXA yield 100% versus control (3100 vs 1520 mg/g). On the other hand, both maize and cowpea anthocyanins were unstable and rapidly degraded under MAE. Cell wall-derived ferulate esters were detected in sorghum and maize MAE extracts, indicating cell wall degradation occurred during MAE. Thus the enhanced extraction of 3-DXA under MAE was due to their structural stability, along with improved diffusion from cell matrix due to microwave-induced sorghum cell wall disruption.

Effects of different industrial processes on the phenolic composition of white and brown teff (Eragrostis tef (Zucc.) Trotter)

Teff is currently being incorporated into a range of foodstuffs, especially gluten-free flakes and extruded products. The main objective of this work was to assess the effects of different treatments (industrial milling, formation of flakes and extrusion) on the phenolic composition of two types of teff grains differing in their colour (white and brown). Fifty-nine phenolic compounds were detected by HPLC-DAD-MSⁿ. C-glycosyl flavones accounted for more than 90% of the total phenolic contents in both teff types. White teff mostly contained apigenin-derived flavones (86-92%), whereas luteolin derivatives prevailed in brown teff (91-94%). The industrial processes, mainly flaking and extrusion, caused marked changes in the phenolic composition, some of which were dependent on the teff type. In both teff types, processing changed the phenolic profiles similarly by increasing C-monoglycosyl flavones and decreasing acylated derivatives. However, the total content was increased in flakes and extruded products made only from brown teff grains.

Flavonoids in Decorticated Sorghum Grains Exert Antioxidant, Antidiabetic and Antiobesity Activities

Eight new genotypes of brown sorghum grain were decorticated and assessed for their antioxidant, antidiabetic and antiobesity activities in vitro. The DPPH and ABTS radical scavenging assays of the soluble fractions were evaluated, followed by digestive enzymes and advanced glycation end-products (AGEs) formation inhibition assays. DSOR 33 and DSOR 11 exhibited the highest DPPH (IC50 = 236.0 ± 1.98 µg/mL and 292.05 ± 2.19 µg/mL, respectively) and ABTS radical scavenging activity (IC50 = 302.50 ± 1.84 µg/mL and 317.05 ± 1.06 µg/mL, respectively). DSOR 17, DSOR 11 and DSOR 33 showed significantly higher inhibitory activity of both α-glucosidase and α-amylase (IC50 = 31.86, 35.10 and 49.40 µg/mL; and 15.87, 22.79 and 37.66 µg/mL, respectively) compared to acarbose (IC50 = 59.34 and 27.73 µg/mL, respectively). Similarly, DSOR 33, DSOR 11 and DSOR 17 showed potent inhibition of both AGEs and lipase with IC50 values of 18.25, 19.03 and 38.70 µg/mL; and 5.01, 5.09 and 4.94 µg/mL, respectively, compared to aminoguanidine (52.30 µg/mL) and orlistat (5.82 µg/mL). Flavonoids were the predominant compounds identified, with flavones being the major subclass in these three extracts. Our findings suggest that decorticated sorghum grains contain substantial amounts of flavonoids and could be promising candidates for the prevention and treatment of diabetes and obesity.

Effects of edible plant polyphenols on gluten protein functionality and potential applications of polyphenol-gluten interactions

Expanding plant-based protein applications is increasingly popular. Polyphenol interactions with wheat gluten proteins can be exploited to create novel functional foods and food ingredients. Polyphenols are antioxidants, thus generally decrease gluten strength by reducing disulfide cross-linking. Monomeric polyphenols can be used to reduce dough mix time and improve flexibility of the gluten network, including to plasticize gluten films. However, high-molecular-weight polyphenols (tannins) cross-link gluten proteins, thereby increasing protein network density and strength. Tannin-gluten interactions can greatly increase gluten tensile strength in dough matrices, as well as batter viscosity and stability. This could be leveraged to reduce detrimental effects of healthful inclusions, like bran and fiber, to loaf breads and other wheat-based products. Further, the dual functions of tannins as an antioxidant and gluten cross-linker could help restructure gluten proteins and improve the texture of plant-based meat alternatives. Tannin-gluten interactions may also be used to reduce inflammatory effects of gluten experienced by those with gluten allergies and celiac disease. Other potential applications of tannin-gluten interactions include formation of food matrices to reduce starch digestibility; creation of novel biomaterials for edible films or medical second skin type bandages; or targeted distribution of micronutrients in the digestive tract. This review focuses on the effects of polyphenols on wheat gluten functionality and discusses emerging opportunities to employ polyphenol-gluten interactions.

Comprehensive identification and quantification of unexploited phenolic compounds from red and yellow araçá (Psidium cattleianum Sabine) by LC-DAD-ESI-MS/MS

LC-DAD-ESI-MS/MS was used to comprehensively characterise the non-extractable phenolic compounds (NEPC) in red and yellow araçá genotypes. Results showed a total of 45 and 43 phenolic compounds in the NEPC fraction and, similarly, 51 and 50 compounds in extractable phenolic compounds (EPC) fraction from red and yellow araçá, respectively. Gallic acid and ellagic acid were the unique compounds found in both fractions. The NEPC fraction represented about 35% (m/m) of the total phenolic content and was characterised by an abundance of phenolic acids, while the EPC fraction was rich in flavanols. Although NEPC represented one-third of the total phenolic compounds found in araçá, its antioxidant capacity (against peroxyl radical) was 50% higher than the EPC fraction. The results of this work show that the NEPC fraction of araçá has great diversity and a relatively high concentration of low-molecular-weight phenolic compounds with high antioxidant capacity.

Recent Trends in the Application of Chromatographic Techniques in the Analysis of Luteolin and Its Derivatives

Luteolin is a flavonoid often found in various medicinal plants that exhibits multiple biological effects such as antioxidant, anti-inflammatory and immunomodulatory activity. Commercially available medicinal plants and their preparations containing luteolin are often used in the treatment of hypertension, inflammatory diseases, and even cancer. However, to establish the quality of such preparations, appropriate analytical methods should be used. Therefore, the present paper provides the first comprehensive review of the current analytical methods that were developed and validated for the quantitative determination of luteolin and its C- and O-derivatives including orientin, isoorientin, luteolin 7-O-glucoside and others. It provides a systematic overview of chromatographic analytical techniques including thin layer chromatography (TLC), high performance thin layer chromatography (HPTLC), liquid chromatography (LC), high performance liquid chromatography (HPLC), gas chromatography (GC) and counter-current chromatography (CCC), as well as the conditions used in the determination of luteolin and its derivatives in plant material.

Development of healthy gluten-free crackers from white and brown tef (Eragrostis tef Zucc.) flours

This study evaluated the effect of inclusion of two types of tef flours (white and brown) at different levels (25, 50 and 100 %, total flour) on the nutritional (proximal and mineral composition), in vitro bioactive (antioxidant capacity and starch digestibility) and sensory properties of rice-tef crackers. The aim was to formulate a gluten-free product with nutritional and healthy benefits, and acceptable for consumers. Results showed than crackers enriched with white tef had a significant (p ≤ 0.05) higher concentration of all the minerals tested, except for calcium and manganese, compared to brown tef. Iron content of white tef was almost twice that of brown tef, and copper and magnesium increased from 0.12 mg/100 g and 39.2 mg/100 g in control crackers to 0.56 mg/100 g and 197 mg/100 g in white tef crackers (WT 100%), respectively. Moreover, white tef flour and crackers showed significantly higher antioxidant activity than rice or brown tef counterparts. Formulation with tef flour significantly contributed to a reduction of the rapidly available glucose and rapidly digestible starch of crackers.

Optimization of an Ultrasound-Assisted Extraction for Simultaneous Determination of Antioxidants in Sesame with Response Surface Methodology

Sesame is a nutritional agricultural product with medicinal properties. Accurate determination of micronutrients is important for the improvement of sesame quality and nutrition assessments. Our previous study showed that 10 antioxidants—d-homoproline, vitamin B₂, coniferyl aldehyde, hesperidin, phloretin, N-acetyl-l-leucine, l-hyoscyamine, ferulic acid, 5-methoxypsoralen, and 8-methoxypsoralen—in sesame were potential characteristic nutrients in sesame. Herein, simultaneous detection of 10 different types of antioxidants was developed by using ultrasound-assisted extraction coupled with liquid chromatography-tandem mass spectrometry (UAE-LC-MS/MS) with the help of response surface methodology. The significant variables and levels were screened and optimized by combining the single factor experiment, Plackett–Burman test, and Box–Behnken design. The optimal conditions for extraction of target antioxidants in sesame were methanol solution of 75.0%, liquid-to-material ratio of 20:1 (mL/g), extraction temperature of 50 °C, extraction power of 410.0 W, extraction time of 65 min. The total yield of targets was 21.74 μg/g under the optimized conditions. The mobile phase used was 0.1% formic acid in acetonitrile and 0.1% formic acid in water, and the column was a Thermo Syncronis C18 reverse phase column (100 mm × 2.1 mm, 3 μm). All targets required only one injection and could be quickly separated and assayed within 7 min. The limits of detection and limits of quantification for these 10 nutritional compounds ranged from 0.01 to 0.11 µg/kg and from 0.04 to 0.34 µg/kg, respectively. The validation results indicated that the method had reasonable linearity (R² ≥ 0.9990), good recoveries (71.1%–118.3%), satisfactory intra-day precision (≤9.6%) and inter-day precision (≤12.9%), and negligible matrix effects (≤13.8%). This simultaneous quantification method was accurate, fast, and robust for the assessment of sesame nutrition.

Variations in Amino Acid and Protein Profiles in White versus Brown Teff (Eragrostis Tef) Seeds, and Effect of Extraction Methods on Protein Yields

Data on variations in amino acid compositions and protein profiles among white and brown teff, a grain of growing interest, is either limited or contradicting at the moment. In this study, three white (Addis-W, Mekel-W and Debre-W) and three brown (Addis-B, Mekel-B and Debre-B) teff seed samples were used for whole flour amino acid analysis and protein fractionation with three different methods. White and brown seed types showed different physical changes during protein extraction. Brown teff displayed higher essential amino acid content than white with lysine present in high concentration in both seed types. Extraction with tert-butanol increased prolamin yields in teff compared to ethanol. The major protein fraction in teff was glutelin with white teff containing higher glutelin proportion than brown. Sodium Dodecyl Sulfate Gel Electrophoresis (SDS-PAGE) analysis revealed clear genetic variability between white and brown teff seed types.

Fabrication of BSA-Pinus koraiensis polyphenol-chitosan nanoparticles and their release characteristics under in vitro simulated gastrointestinal digestion

BSA and chitosan were used to prepare nanoparticles of polyphenols from the pine cones of Pinus koraiensis (PKP-NPs).

Physicochemical properties, bioaccessibility and antioxidant activity of the polyphenols from pine cones of Pinus koraiensis

This study investigated the physicochemical properties, bioaccessibility and in vitro antioxidant ability of the polyphenols isolated from the pine cones of Pinus koraiensis (PKP) under the simulated gastrointestinal digestion. The results found that PKP was mainly composed by derivatives of apigenin, phloretin, quercetin, myricetin, ellagitannin, and chlorogenic acid, and possessed the flat and smooth lump surface morphology. Through respective establishment of saliva, gastric fluid and small intestinal fluid digestive model in vitro, the compositions of phenolic compounds were totally different due to biotransformation. Compared with the phenolic composition of undigested PKP, the derivatives of apigenin, quercetin and ellagitannin were still detected after simulated digestion. A decrease of antioxidant capacity on free radical in vitro was observed throughout the simulated digestion processes, corresponding to the variation in phenolic content and composition. Our results highlighted that gastrointestinal digestion process might essentially influence the absorption of polyphenols, leading to the reduction of bioavailability.

Combined cereal and pulse flavonoids show enhanced bioavailability by downregulating phase II metabolism and ABC membrane transporter function in Caco-2 model

Predominant flavonoids in cereals and pulses are structurally different and may positively interact to enhance bioactivity in combined diet. This work investigated the effects of combined cereal 3-deoxyflavonoids (apigenin, naringenin) and pulse flavonols (quercetin), along with natural extracts, on their bioavailability and underlying mechanisms using Caco-2 monolayer model. Membrane permeability, phase II metabolism, and ATP binding cassette (ABC) membrane transporter expression and function were measured. Apparent absorption of quercetin and apigenin increased (p < 0.05) 3.3× and 1.5×, respectively, while both compounds were significantly less metabolized in combined treatments. Combinations with naringenin had insignificant effect, suggesting a role for flavonoid C2C3 conjugation. Both natural extracts and apigenin-quercetin combinations synergistically (3-40 fold) downregulated ABC transporter expression, and inhibited P-glycoprotein activity, suggesting direct binding and inhibition of ATPase. Combination of conjugated cereal and pulse flavonoids enhances their potential bioavailability through synergistic inhibition of membrane transporter and phase II enzyme function.

Gluten-free flours from cereals, pseudocereals and legumes: Phenolic fingerprints and in vitro antioxidant properties

The interest in gluten-free (GF) products increases together with the increase in gluten-sensitive people. However, GF foods might have decreased nutritional quality as compared to the gluten containing counterparts. In this work, an investigation of the phenolic and antioxidant profile in 18 GF flours belonging to legumes, cereals and pseudocereals was achieved. Significant differences could be observed across samples. Total phenolic content was highest in violet rice flours, whereas total anthocyanins were highest in violet, nerone, and black rice flours. FRAP and ORAC antioxidant activities were correlated to phenolic contents and found to be higher in violet rice flours. Metabolomics highlighted a wide diversity in phenolics, with flavonoids (197 compounds ascribable to anthocyanins, flavones, flavanones, isoflavonoids, flavonols, and flavanols), phenolic acids (74 compounds belonging to hydroxycinnamics, hydroxybenzoics, and hydroxyphenylacetics), and tyrosol derivatives the most represented. Finally, OPLS-DA multivariate statistics outlined flavonoids, furofurans and phenolic acids as the most discriminant phenolics.