Characterization and Bile Acid Binding Capacity of Dietary Fiber Obtained from Three Different Amaranth Products.

Amaranth is a dicotyledonous plant, now considered a health-promoting food. It has been rediscovered by the worldwide food industry, which is increasingly becoming aware of the many uses and benefits provided by amaranth in various food preparations. Amaranth dietary fibers, soluble and insoluble fractions, obtained from flour, protein isolate, and beverage were physicochemically characterized and their potential bile acid binding capacity was evaluated. Primary bile acids binding to fiber might contribute to a hypocholesterolemic effect, while the binding of secondary bile acids could minimize the cytotoxic effect that these metabolites exert on the colon. Amaranth fiber fractions were capable of sequestering cholate, taurocholate, deoxycholate, and bovine bile, with a percentage depending not only on the origin and the type of amaranth fiber evaluated but also on the bile acid studied. Flour fiber and the protein isolate insoluble fractions were the most efficient for binding bile and bile acids with uptake values between 29 and 100% relative to cholestyramine. Moreover, deoxycholate, a hydrophobic secondary bile acid, was the most captured by all the fractions, reaching 100% uptake with total and insoluble fibers of the three amaranth products. These results would suggest that the main effect through which amaranth fiber binds bile acids corresponds to an adsorptive effect mediated by hydrophobic interactions.

Amaranth Lemon Sorbet, Elaboration of a Potential Functional Food.

In the present work, amaranth proteins were used as a functional ingredient of formulated food. An amaranth lemon sorbet, a healthy alternative dessert for celiac, vegan and any consumer that chooses to follow a conscious diet, was elaborated and characterized. The sorbet base mixture behaved like a pseudoplastic and thixotropic fluid, with a Kokini viscosity of 0.42 ± 0.07 Pa.s, a suitable value for elaborating products with good thickness characteristics. Aeration rate of the sorbet was 36.15 ± 3.48, an overrun value within the expected range of 30-50%, indicating that amaranth proteins presented adequate foaming properties in low pH elaboration conditions. Moreover, the stability study showed that the sorbet did not suffer significant changes in its structure over time during the first two months of storage at -20 °C. Sensory evaluation evidenced panelists accepted the product (8 ± 1, acceptability assay) and related it with airy, creamy and healthy attributes (CATA assay). Finally, simulated gastrointestinal digestion was able to release peptides capable of inhibiting fibrin clot formation (IC50 = 3.4 ± 0.1 mg protein/mL), demonstrating that amaranth proteins could be used as a good foaming ingredient in the elaboration of potential functional foods with antithrombotic activity.

Antiproliferative Effect of Amaranth Proteins and Peptides on HT-29 Human Colon Tumor Cell Line.

Antiproliferative effect of Amaranthus mantegazzianus proteins and peptides released after simulated gastrointestinal digestion (DH% 37.8 ± 3.8) was investigated on human colon cancer cell line HT-29. Inhibition of proliferation of HT-29 cells was exhibited after a 24 h treatment with different concentrations of amaranth protein isolate (API) and the peptides released after digestion (DGS), presenting IC50 values of 1.35 ± 0.12 and 0.30 ± 0.07 mg soluble protein/mL, respectively. Lactate dehydrogenase assay indicated that both samples caused the loss of membrane integrity and cell lysis over HT-29 cells, and DAPI fluorescence microscopies evidenced typical apoptotic features. Moreover, Annexin V-FITC flow cytometry showed a significant increase of early apoptotic and late apoptotic/necrotic HT-29 cells compared to untreated ones, and caspase-3 assay confirmed the apoptosis induction with a 43.0 ± 10.3 and 65.8 ± 12.7% increase of caspase-3 activity produced by a 2 mg/mL treatment of API and DGS, respectively. In conclusion, amaranth peptides successfully released after simulated gastrointestinal digestion would exert a potential antiproliferative activity over HT-29 tumor cells. This effect was linked to the induction of cell necrosis and apoptosis, supporting the idea of using amaranth proteins as a potential food alternative ingredient for functional foods.

Antithrombotic Effects of Amaranthus hypochondriacus Proteins in Rats.

Cardiovascular disease (CVD) is a major cause of disability and premature death throughout the world. Diets with antithrombotic components offer a convenient and effective way of preventing and reducing CVD incidence. The aim of the present work was to assess in vivo and ex vivo effects of Amaranthus hypochondriacus proteins on platelet plug formation and coagulation cascade. Amaranth proteins were orally administrated to rats (AG, 8 animals) and bleeding time was determined showing no significant difference compared with control rats (CG, 7 animals). However, results show a strong tendency, suggesting that amaranth proteins are involved in the inhibition of thrombus formation. Non-anticoagulated blood extracted from animals was analyzed with the hemostatometer, where AG parameters obtained were twice the values showed by CG. The clotting tests, thrombin time (TT) and activated partial thromboplastin time (APTT), presented a 17 and 14% clotting formation increase respectively when comparing AG with CG. The ex-vivo assays confirm the hypothesis inferring that amaranth proteins are a potential antithrombotic agent.

Antithrombotic and Antioxidant Activity of Amaranth Hydrolysate Obtained by Activation of an Endogenous Protease.

Ingestion of diets with antithrombotic and antioxidant components offer a convenient and effective way to prevent and reduce the incidence of cardiovascular diseases. The aim of the present work was to obtain an amaranth hydrolysate by the activation of an endogenous aspartic protease, to establish adequate experimental conditions, and to evaluate its antithrombotic and antioxidant activity in order to assess its potential application as an ingredient in functional foods. The results obtained not only confirmed the presence of an endogenous protease in the amaranth isolate, but also allowed us to select an adequate incubation conditions (pH 2, 40 °C, 16 h). The hydrolysate obtained (degree of hydrolysis 5.3 ± 0.4 %) showed potential antithrombotic activity (IC50 = 5.9 ± 0.1 mg soluble protein/mL) and had more antioxidant activity than the isolate, indicating that the activation of the protease released bioactive peptides from amaranth proteins. Decreasing the pH is a simple and cheap process and is another way to obtain potential functional ingredients with bioactive compounds.

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.

Amaranth peptides decreased the activity and expression of cellular tissue factor on LPS activated THP-1 human monocytes.

The effect of amaranth peptides on the activity and expression of tissue factor (TF) on THP-1 activated cells was evaluated in vitro. An active anticoagulant peptide fraction (AF) was found to inhibit TF expression (IC50 = 0.39 mg mL-1) and activity. Immunocytochemical fluorescence confocal microscopy analysis showed that treated monocytes decreased TF membrane translocation by 49.0% and increased two-fold in nuclei compared to a positive control, indicating a decrease of active TF to initiate the coagulation cascade. Moreover, a cytokine array suggested that the AF mechanism of action implied the inhibition of the NF-κB pathway. Expression of MIP-3α, interleukin-1ß, interleukin-1α, TARC, pentaxin 3, and PDGF-AA cytokines was highly suppressed by AF peptides, producing reductions of 78.8%, 61.8%, 54.1%, 42.6%, 37.9% and 37.8%, respectively, compared to a positive control. The results suggest a potential mechanism for the antithrombotic and anti-inflammatory effect of AF, by showing that amaranth peptides play a negative feedback regulatory role over the NF-κB pathway. In this research, we link for the first time the immunomodulatory activity of amaranth peptides with the inhibition of TF expression and therefore their antithrombotic potential.

Amaranth proteins foaming properties: Film rheology and foam stability - Part 2.

In this work the influence of pH and ionic strength on the stability of foams prepared with amaranth protein isolate was analyzed. The behaviour observed was related to the physico-chemical and structural changes undergone by amaranth protein as a result of those treatments. The results obtained show that foams prepared at acidic pH were more stable than the corresponding to alkaline pH. At pH 2.0 the foams presented higher times and more volumes of drainage. This behaviour is consistent with the characteristics of the interfacial film, which showed a higher viscoelasticity and a greater flexibility at acidic pH than alkaline pH value, which in turn increased by increasing the concentration of proteins in the foaming solution. It is also important to note that the presence of insoluble protein is not necessarily detrimental to the properties of the foam. Detected changes in the characteristics of the interfacial film as in the foam stability have been attributed to the increased unfolding, greater flexibility and net charge of amaranth proteins at acidic conditions.

Functional properties of guava seed glutelins.

Five guava seed glutelin extracts were obtained with different buffer solutions: Na(2)B(4)O(7) alone (Glut.Bo) or containing SDS (Glut. BoSDS), 2-mercaptoethanol (Glut.Bo2-ME), or a combination of both (Glut. BoSDS2-ME) and NaOH (Glut.Na). All borate buffer solutions were at pH 10. The higher yield of glutelins corresponded to the Glut. BoSDS extract (81.9% dry basis) and the lower to Glut.Bo (6.8%). The functional properties of the five guava seed glutelin extracts were determined. Glut. BoSDS, Glut. BoSDS2-ME, and Glut.Na showed high values for several properties, including surface hydrophobicity (7.7, 10.8, and 0.6, respectively), solubility at pH 10 (91.1, 77.9, and 96.7, respectively), water-holding capacity at pH 3.6 (1.7, 2.5, and 2.8, respectively), emulsifying activity index (pH 10; 503.5, 238.2, and 838.0, respectively), and foaming properties (pH 10; V(0) = 0.14, 0.25, and 0.19, respectively; V(max) = 6.1, 5.59, and 4.51, respectively; t(1/2) = 266, 255.3, and 94 s, respectively). These results suggest that the denaturing reagent (SDS or NaOH) during extraction conferred on the proteins a structure that facilitated the development of their functional properties.

Amaranth proteins foaming properties: adsorption kinetics and foam formation--part 1.

This work has focused on the study of the relationships between the structural changes in proteins of amaranth under different conditions of pH and ionic strength and the ability to form foam, also taking into consideration the kinetics of adsorption of proteins at the interface. Results showed that treatment at pH 2.0 significantly improves the foaming properties of amaranth proteins. The structural studies performed indicate that amaranth proteins at acidic pH are denatured, dissociated and undergo partial hydrolysis due to the existence of an endoprotease. They also present a lower content of ß-sheet and random coil secondary structures. Diffusion-adsorption studies of proteins at the air:water interface allowed to determine that the acidic pH favors adsorption thereof (higher values of kdiff and ka) and reduces the need for a rearrangement (higher values of γr). The interfacial behavior of amaranth proteins is a direct consequence of the structural changes they undergo at acidic pH, changes that also were reflected on the increased foaming capacity (higher vo) thus forming more dense and homogeneous foams. The behavior of the soluble proteins as surfactants was not altered by the presence of protein aggregates and insoluble proteins.