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.

Simulated gastrointestinal digestion of amaranth flour and protein isolate: Comparison of methodologies and release of antioxidant peptides.

The effect of both the simulated gastrointestinal digestion conditions and the matrix over protein hydrolysis and antioxidant peptides generation was evaluated by comparing an in-house method with COST INFOGEST-based SGD protocols. The in-house protocol was used to digest amaranth protein isolate I (Id1), while the standardized method and a modified version (similar enzyme/substrate ratio than in our lab) were used to digest I and amaranth flour F (Id3 and Fd3, Id2 and Fd2). Protein hydrolysis degree (TNBS method) was similar for the three I digested (about 60%), but lower for F digested (45 and 34% for Fd2 and Fd3, respectively). The five digested obtained presented comparable protein solubility and only small differences in the polypeptide/peptide composition (SDS-PAGE, tricine-SDS-PAGE, gel filtration FPLC), similar antioxidant activity by the ORAC assay (IC50 values between 0.023 and 0.034 mg.mL-1) and some mild differences by the HORAC assay (IC50 values between 1.13 and 1.30 mg.mL-1 for Id1, Fd2, and Fd3; 1.50 mg.mL-1 for Id2; 1.61 mg.mL-1 for Id3). All the FPLC fractions presented high ORAC activity, while only fractions between 0.43 and 3.5 kDa showed HORAC activity (due to peptide concentration). Differences in activity and potency among fractions were registered, especially for F digested. The modification of digestion conditions produced only small differences in the molecular composition but did not affect the proteolysis degree and the antioxidant activity in the case of digested from protein isolate. The presence of other components and changes in the digestion method had an impact on proteolysis, composition and antioxidant activity of flour digested.

Effects of the Dietary Addition of Amaranth (Amaranthus mantegazzianus) Protein Isolate on Antioxidant Status, Lipid Profiles and Blood Pressure of Rats.

The effects of the dietary addition of 2.5% (w/w) Amaranthus mantegazzianus protein isolate (AI) on blood pressure, lipid profiles and antioxidative status of Wistar rats were evaluated. Six diets were used to feed animals during 28 days: (base (AIN93G), Chol (cholesterol 1%, w/w), CE (α-tocopherol 0.005%, w/w), CholE (cholesterol 1% (w/w) + α-tocopherol 0.005%, w/w), CAI (AI 2.5% w/w), CholAI (cholesterol 1% (w/w) + AI 2.5%, w/w). Lipid profiles of plasma and liver and faecal cholesterol content were analyzed. Antioxidant status was evaluated by the ferric reducing activity of plasma (FRAP), the 2-thiobarbituric acid (TBA) assay and superoxide dismutase (SOD) activity in plasma and liver. Blood pressure was measured in the tail artery of rats. CholA group presented a significant (α < 0.05) reduction (16%) in the plasma total cholesterol. In liver, the intake of cholesterol (Chol group) induced a significant increment in cholesterol and triglycerides (2.5 and 2.3 times, respectively), which could be decreased (18% and 47%, respectively) by the addition of AI (CholA group). This last group also showed an increased faecal cholesterol excretion (20%). Increment (50%) in FRAP values, diminution of TBA value in plasma and liver (70% and 38%, respectively) and diminution of SOD activity (20%) in plasma of CholA group suggest an antioxidant effect because of the intake of AI. In addition, CA and CholA groups presented a diminution (18%) of blood pressure after 28 days.