Amaranth grain as a potential source of biologically active peptides: a review of their identification, production, bioactivity, and characterization

Nutritional and functional perspectives of pseudocereals

An increase in the consumption of carbohydrate-rich cereals over past few decades has led to increased metabolic disorders in population. This nutritional imbalance in diets may be corrected by substituting cereal grains with pseudocereals that are richer in high-quality proteins, dietary fibers, unsaturated fats, and bioactive compounds (e.g., polyphenols and phytosterols) as compared to cereal grains. These nutrients have been associated with numerous health benefits, such as hypolipidemic, anti-inflammatory, anti-hypertensive, anti-cancer, and hepatoprotective properties, and benefits against obesity and diabetes. In this review, the nutritional composition and health benefits of quinoa, amaranth, and buckwheat are compared against wheat, maize, and rice. Subsequently, the processing treatments applied to quinoa, amaranth, and buckwheat and their applications into food products are discussed. This is relevant since there is substantial market potential for both pseudocereals and functional foods formulated with pseudocereals. Despite clear benefits, the current progress is slowed down by the fact that the cultivation of these pseudocereals is limited to its native regions. Therefore, to meet the global needs, it is imperative to support worldwide cultivation of these nutrient-rich pseudocereals.

Amaranth proteins: From extraction to application as nanoparticle-based delivery systems for bioactive compounds

Amaranth proteins can be produced more sustainably than animal proteins, and they have amino acid compositions that are nutritionally balanced, which makes them attractive candidates for various applications in the food and pharmaceutical industries. This article provides an overview of the composition and techno-functional properties of amaranth protein, including its solubility, emulsification, gelation, foaming, and binding properties. These properties play an important role in the use of amaranth proteins for formulating nanoparticle-based delivery systems with good functional attributes. Amaranth proteins have structural and physicochemical properties suitable for fabricating protein-based nanoparticles. These nanoparticles can be used to encapsulate and control the release of bioactive compounds. However, challenges associated with the presence of anti-nutritional factors in amaranth proteins need to be addressed. These antinutrients negatively affect the bioavailability and digestibility of proteins and bioactive compounds. Hence, strategies to mitigate these challenges are discussed, including processing technologies and genetic engineering methods.

Chemical and cell antioxidant activity of amaranth flour and beverage after simulated gastrointestinal digestion. Role of peptides

The potential of peptides generated by simulated gastrointestinal digestion (SGID) of two products derived from Amaranthus manteggazianus seeds, flour (F) and beverage (B), to exert peroxyl scavenging activity (ORAC) and antioxidant action on intestinal cells was studied. B was prepared by solubilisation of seed proteins, with the addition of gums and the application of a pasteurization treatment. The gastrointestinal digests FD and BD showed some differences in the peptide/polypeptide composition. The SGID produced increased ORAC activity for both samples, with some differences in the ORAC of the whole digests BD and FD and of some gel filtration fractions. Bioaccessible fractions (FDdbs and BDdbs) were obtained after treatment with cholestyramine resin to remove bile salts due to their cytotoxicity and oxidative effect. BDdbs presented a greater ORAC potency (IC50: 0.05 ± 0.01 and 0.008 ± 0.004 mg protein/ml for FDdbs and BDdbs, respectively). These fractions showed low cytotoxicity values (measured by LDH release) and produced high intracellular ROS inhibition (around 80 %), increased the SOD activity and the GSH content, with no effect on GPx activity in Caco2-TC7 cells exposed to H2O2. Several fractions with MM < 2.2 kDa presented also these cellular actions; fractions from FD induced higher increases in GSH concentration. Amaranth flour and a processed matrix like the beverage are shown as sources of bioactive peptides with potential cell antioxidant activity.

Amaranth proteins and peptides: Biological properties and food uses

Amaranthus grains have attracted great attention due to its attractive health benefits. The grains have processing properties (e.g., starch related properties) similar to those of common cereals. Amaranth grains are gluten free and protein is a significant component of these grains. Proteins of the grains have been used in various food applications such as formulations of edible films and emulsions for controlled release of bioactive compounds. The proteins have been hydrolyzed using different enzymes to produce peptides and hydrolysates, which showed a range of biological functions including anti-hypertensive and antioxidant activities among others. They have been formulated into staple foods including breads and pastas for improved nutritional quality. This review summarizes the recent advances of the last 5 years in understanding the biological functions and food applications of proteins, protein hydrolysates and peptides from the grains of different Amaranthus species. Limitations in the studies summarized are critically discussed with an aim to improve the efficiency in amaranth grain protein and peptide research.

Production, health-promoting properties and characterization of bioactive peptides from cereal and legume grains

The search for bioactive components for the development of functional foods and nutraceuticals has received tremendous attention. This is due to the increasing awareness of their therapeutic potentials, such as antioxidant, anti-inflammatory, antihypertensive, anti-cancer properties, etc. Food proteins, well known for their nutritional importance and their roles in growth and development, are also sources of peptide sequences with bioactive properties and physiological implications. Cereal and legume grains are important staples that are processed and consumed in various forms worldwide. However, they have received little attention compared to other foods. This review therefore is geared towards surveying the literature for an appraisal of research conducted on bioactive peptides in cereal and legume grains in order to identify what the knowledge gaps are. Studies on bioactive peptides from cereal and legume grains are still quite limited when compared to other food items and most of the research already carried out have been done without identifying the sequence of the bioactive peptides. However, the reports on the antioxidative, anticancer/inflammatory, antihypertensive, antidiabetic properties show there is much prospect of obtaining potent bioactive peptides from cereal and legume grains which could be utilized in the development of functional foods and nutraceuticals.

Cocoa bean shells: a review into the chemical profile, the bioactivity and the biotransformation to enhance their potential applications in foods

During processing, cocoa bean shells (CBS) are de-hulled from the bean and discarded as waste. Undermined by its chemical and bioactive composition, CBS is abundant in dietary fiber and phenolic compounds that may serve the valorization purpose of this by-product material into prebiotic and functional ingredients. In addition, the cell-wall components of CBS can be combined through enzymatic feruloylation to obtain feruloylated oligo- and polysaccharides (FOs), further enhancing the techno-functional properties. FOs have attracted scientific attention due to their prebiotic, antimicrobial, anti-inflammatory and antioxidant functions inherent to their structural features. This review covers the chemical and bioactive compositions of CBS as well as their modifications upon cocoa processing. Physical, chemical, and enzymatic approaches to extract and bio-transform bioactive components from the cell wall matrix of CBS were also discussed. Although nonspecific to CBS, studies were compiled to investigate efforts done to extract and produce feruloylated oligo- and polysaccharides from the cell wall materials.

Identification and characterization of cholesterol esterase and lipase inhibitory peptides from amaranth protein hydrolysates

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Gastric, microbial and plant-based enzymes were used to produce Amaranth protein hydrolysates (APHs).

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APHs displayed enhanced cholesterol esterase (CEase) and pancreatic lipase (PL) inhibitory activities.

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Bromelain generated hydrolysates showed the highest CEase and PL inhibitory activity.

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FPFPPTLGY, FGAPR, and FPFVPAPT were predicted as potential PL inhibitors and FPFVPAPT as CEase inhibitor.

Human diet is undergoing a shift towards plant-based diet as a sustainable source of protein compared to animal-derived protein. In this study, cholesterol esterase (CEase) and pancreatic lipase (PL) inhibitory activities of amaranth protein hydrolysates (APHs) were studied. Bromelain, chymotrypsin, and actinase E were used for generating APHs at 2, 4 & 6 h of hydrolysis. Higher PL inhibiting potential were observed in bromelain-derived APHs (IC₅₀ = 0.38–0.66 mg/mL) in comparison to intact amaranth proteins (IC₅₀ = 3.93 mg/mL). Bromelain-4 h hydrolysates (AB4) demonstrated significant inhibitory potential for both CEase (IC₅₀ = 0.47 mg/mL) and PL (IC₅₀ = 0.48 mg/mL) activity. Peptide identification in AB-4 hydrolysate revealed that among 17 bioactive peptides, three peptides (FPFPPTLGY, FGAPR, and FPFVPAPT) were predicted as potential PL inhibitors and only one peptide (FPFVPAPT) was predicted as CEase inhibitor based on the number of substrate binding sites on active site of the enzymes. This is the first study providing insights into amaranth protein derived bioactive peptide possessing CEase and LIP inhibitory potential.

Relationship of Cultivated Grain Amaranth Species and Wild Relative Accessions

Amaranthus is a genus of C4 dicotyledonous herbaceous plants, and three New World species have been domesticated to produce grain crops with light colored seed which are classified as pseudo-cereals rich in protein and minerals. A core collection of grain amaranths and immediate precursor species has been established, representing the closest related species. The goal of this study was to evaluate the genetic diversity in that collection of cultivated and wild species, using competitive allele single nucleotide polymorphism markers. A secondary objective was to determine the relationships among the three cultivated species and non-domesticated Amaranthus, while a third objective was to evaluate the utility of the markers in detecting diversity in the 276 genotypes. The markers were found to be highly variable with an average polymorphism information content of 0.365. All markers were bi-allelic; and the major allele frequency ranged from 0.388 to 0.871. Population structure analysis of the cultigens revealed the presence of two sub populations. Phylogeny confirmed that the two Mesoamerican species, Amaranthus cruentus and Amaranthus hypochondriacus, were related and distant from the South American species Amaranthus caudatus, which in turn was very closely clustered with Amaranthus quitensis, even though this is considered a weedy relative. The first pair of species were likely to have inter-crossed, while the latter two likely exist in a wild-cultivated hybrid state. In conclusion, the results of this SNP study provided insights on amaranth cultivars and their relationship to wild species, the probable domestication events leading to the cultivars, and possible crop breeding or germplasm conservation strategies.

Amaranth, quinoa and chia bioactive peptides: a comprehensive review on three ancient grains and their potential role in management and prevention of Type 2 diabetes

Worldwide prevalence of Type 2 Diabetes (T2D) has become a major concern with several implications for public health, economy, and social well-being, especially in developing countries. Conventional pharmacological management of T2D have proved effective, but possess underlying side effects, leading the scientific community to research alternative compounds that exert beneficial effects on current therapeutic targets of T2D. Bioactive peptides (BAPs) from food sources, have shown relative advantages in this matter, moreover, BAPs have proved to impart anti-diabetic activity through one or more mechanisms such as enzymatic inhibition of α-glucosidase, α-amylase and DPP-IV. Several plants and animal have been used as protein sources of anti-diabetic BAPs, in the sense of this matter, the pseudo-cereals amaranth and quinoa, along with the ancestral grain chia, have gained attention. Due, to their high protein content and balanced amino-acid composition, along with proved anti-diabetic features, the three seeds are top choices for the obtention of anti-diabetic BAPs. With a comprehensive overview of the most recent reported in silico and in vitro anti-diabetic studies in relation to biomarkers α-glucosidase, α-amylase and DPP-IV, the present review aims to examine the current knowledge of amaranth, quinoa and chia derived anti-diabetic BAPs and their effects on T2D therapeutic markers.

Antioxidant effect of amaranth flour or protein isolate incorporated in high-fat diets fed to Wistar rats. Influence of dose and administration duration

This study evaluated the effect on Wistar rat's oxidative status of incorporating amaranth flour (AF) and protein isolate (AI) in increased-fat diets. Five of the groups were fed for 4 weeks with either BD (basal diet), Chol+F (2% cholesterol, 10% porcine fat), Chol+F+E (0.005% α-tocopherol), Chol+F+AF₁ or Chol+F+AI₁ (25% of protein replacement) diets. The other two groups were fed for 4 weeks with Chol+F and then 1 week with Chol+F+AF₂ or Chol+F+AI₂ diet (50% of protein replacement). Various effects on the oxidative stress biomarkers in tissues (intestine and liver) were observed. These effects were dependent on the ingredients, dose, and administration time. In the intestinal cells, Chol+F+AF₁ and Chol+F+AI₂ produced an increment in the reduced glutathione (GSH) content (56% and 39%, respectively), while Chol+F+AF₂ induced an increment in the superoxide dismutase (SOD) (25%) and glutathione peroxidase (GPx) (46%) activities. The presence of certain components in flour (e.g., fiber, polyphenols, squalene) could explain the higher activity recorded for AF. In the liver, Chol+F+AF₂ produced a decrease in SOD (19%) and GSH (36%), as well as an increase in GPx (255%); Chol+F+AI₁ and Chol+F+AI₂ also produced a decrease in GSH (36% and 24%, respectively) and important increments in GPx activity (273% for Chol+F+AI₁ and 2,900% for Chol+F+AI₂ ). These effects were dependent on the AI dose and were probably produced by absorbed peptides. PRACTICAL APPLICATIONS: It is known that redox imbalances are involved in the genesis of many chronic diseases. Therefore, it is possible to prevent them or limit their severity by improving the body's antioxidant defense mechanisms through dietary incorporation of antioxidant substances. The results suggest that amaranth protein isolate and amaranth flour have the potential for regulating intestinal and liver cells redox balance; effects were more evident when they contributed 50% of the diet's protein content and were administered for 1 week. Both amaranth ingredients could be used as ingredients in the development of functional foods with beneficial antioxidant properties.

Bioactive peptides from food fermentation: A comprehensive review of their sources, bioactivities, applications, and future development

Bioactive peptides (BPs) are specific protein fragments that exert various beneficial effects on human bodies and ultimately influence health, depending on their structural properties and amino acid composition and sequences. By offering promising solutions to solve diverse health issues, the production, characterization, and applications of food-derived BPs have drawn great interest in the current literature and are of particular interest to the food and pharmaceutical industries. The microbial fermentation of protein from various sources is indubitably a novel way to produce BPs with numerous beneficial health effects. Apart from its lower cost as compared to enzymes, the BPs produced from microbial fermentation can be purified without further hydrolysis. Despite these features, current literature shows dearth of information on the BPs produced from food via microbial fermentation. Hence, there is a strong necessity to explore the BPs obtained from food fermentation for the development of commercial nutraceuticals and functional foods. As such, this review focuses on the production of BPs from different food sources, including the extensively studied milk and milk products, with emphasis on microbial fermentation. The structure-activity (antihypertensive, antioxidant, antimicrobial, opiate-like, anti-inflammatory, anticancer/antiproliferative, antithrombotic, hypolipidemic, hypocholesterolemic, and mineral binding) relationship, potential applications, future development, and challenges of BPs obtained from food fermentation are also discussed.

Amaranth as a bread enriching ingredient

Amaranth is a promising raw material for enriching foods with protein, minerals, vitamins, dietary fibre, squalene, and other nutrients. However, its varieties differ significantly in composition and properties. The research included two stages. At first, we studied the composition of eight amaranth varieties grown in a collection nursery of Voronezh State Agrarian University. Their composition was a factor that determined their functional use as an enriching ingredient. We found that amaranth grain of the Universal variety could be best used to increase the biological value of foods, whereas the Universal and Valentina varieties could be recommended as multifunctional ingredients. The addition of enriching ingredients into foods, including breads, often leads to changes in their traditional consumer properties. Therefore, our next step was to study changes in the composition of Universal amaranth during extrusion using IR spectroscopy. Also, we assessed the effect of amaranth extrudate on the baking properties of model wheat flour and extrudate mixtures as the main factor of the product’s consumer properties. The results showed a redistribution of moisture between flour gluten proteins and extrudate dietary fibre. We also established amounts of amaranth extrudate needed to ensure the preservation of crumb appearance and structure close to the traditional ones.

Polyphenols and antioxidant activity in pseudocereals and their products

Pseudocereals are important as gluten-free crops that could be utilized as functional foods. They contain proteins with high biological value and also bioactive compounds such as phenolic compounds, flavonoids, vitamins, and minerals that can possess positive health effects on the body. Three types of pseudocereals (amaranth, buckwheat, and quinoa) were evaluated for polyphenols and antioxidant activity. Spectrophotometric methods were used for the determination of free phenols amount with Folin-Ciocalteu reagent, and total antioxidant capacity (TAC) with DPPH and ABTS reagents. Free phenols, the predominant part of polyphenols, were in pseudocereals in the range from 12.4 to 678.1 mg GAE.100g-1. The highest content of FP was found in buckwheat products (146.8 - 678.1 mg GAE.100g-1); quinoa and amaranth products reached much lower values (up to 226.1 mg GAE.100g-1). Antioxidant activity was in an agreement with the FP amounts order, the highest TAC values were again for buckwheat products (167.3 - 473.9 and 876.9 - 3524.8 mg TE.100g-1), followed by quinoa (78.2 - 100.6 and 738.9 - 984.5 mg TE.100g-1) and amaranth ones (25.0 - 69.7 and 118.2 - 431.4 mg TE.100g-1). A high positive correlation between FP amount and TAC values was evaluated for analyzed pseudocereals. The highest content of free phenols and the best antioxidant potential showed buckwheat wholemeal flour, so buckwheat could be characterized as a great source of free phenols with high antioxidant activity.

A biotechnological approach for the production of branched chain amino acid containing bioactive peptides to improve human health: A review

Improper nutrition provokes many types of chronic diseases and health problems, which consequently are associated with particularly high costs of treatments. Nowadays, consumer's interest in healthy eating is shifting towards specific foods or food ingredients. As a consequence, bioactive peptides as a promising source of health promoting food additives are currently an intensely debated topic in research. Process design is still on its early stages and is significantly influenced by important preliminary decisions. Thus, parameters like peptide bioactivity within the product, selection of the protein source, enzyme selection for hydrolysis, peptide enrichment method, as well as stability of the peptides within the food matrix and bioavailability are sensitive decision points, which have to be purposefully coordinated, as they are directly linked to amino acid content and structure properties of the peptides. Branched chain amino acids (BCAA) are essential components for humans, possessing various important physiologic functions within the body. Incorporated within peptide sequences, they may induce dual functions, when used as nutraceuticals in functional food, thus preserving the foodstuff and prevent several widespread diseases. Furthermore, there is evidence that consuming this peptide-class can be a nutritional support for elderly people or improve human health to prevent diseases caused by incorrect nutrition. Based on the knowledge about the role of BCAA within various peptide functions, discussed in the review, special attention is given to different approaches for systematic selection of the protein source and enzymes used in hydrolysis, as well as suitable peptide enrichment methods, thereby showing current trends in research.

Effect of the Incorporation of Amaranth (Amaranthus Mantegazzianus) into Fat- and Cholesterol-Rich Diets for Wistar Rats

The hypocholesterolemic effect of amaranth was studied in male Wistar rats fed a high-fat diet that was supplemented with amaranth flour, AF, or isolated protein, AI. Likewise, an in vitro test was carried out, in which the capacity of the AI, AF, the digested isolate, DAI, and the digested amaranth flour, DAF, to displace the cholesterol of the model micelles was evaluated. The in vivo results showed an increase in the excretion of cholesterol through feces (77% for AF7; 23% and 108% for AI30 and AF30, respect control) and a decrease in the content of hepatic cholesterol (98% for AF7; 96% and 53% for AI30 and AF30 respect control); whereas in vitro it was shown that both AF and DAF have greater power to displace cholesterol than the AI and DAI (IC₅₀ 0.1, 0.71, 0.2, and 2.1 for AF, DAF, AI, and DAI, respectively). These evidences show that the proteins and fibers of amaranth have an effect on cholesterol metabolism. PRACTICAL APPLICATION: Nowadays, consumers give great importance to the effect that food has on health. The results shown in this work evidence the potential hypocholesterolemic activity presented by amaranth, this is of great importance due to the increase in the incidence of dyslipidemia in the world population and the importance of amaranth as a nonextensive crop of excellent agronomic, nutritional, and bioactive properties suitable for preparation of functional foods.