Novel bioactive peptides sequences released by in vitro digestion of proteins isolated from Amaranthus hypochondriacus.

Amaranth is a protein-rich seed, highly consumed in Mexico and reported as a potential source of bio-peptides with physiological function. Therefore, the objective of this study was to evaluate and identify bioactive peptide sequences from amaranth protein fractions released by pepsin and pancreatin in vitro digestion. Multifunctional bioactivities of peptides were measured through antihypertensive, antithrombotic and antioxidant assays. Peptide sequences were identified by analysis with a Nano-LC-ESI-MS/MS. With these results, it was demonstrated that the in vitro enzymatic digestion mechanism allows the release of multifunctional bioactive peptide fractions from amaranth proteins.

Sequence Identification of Bioactive Peptides from Amaranth Seed Proteins (Amaranthus hypochondriacus spp.).

Amaranthus hypochondriacus spp. is a commonly grown cereal in Latin America, known for its high protein content. The objective of this study was to separate and identify bioactive peptides found in amaranth seeds through enzymatically-assisted hydrolysis using alcalase and flavourzyme. Hydrolysis was carried out for each enzyme separately and compared to two-step continuous process where both enzymes were combined. The biological activity of the resulting three hydrolysates was analyzed, finding, in general, higher bioactive potential of the hydrolysate obtained in a continuous process (combined enzymes). Its fractions were separated by RP-HPLC, and their bioactivity was analyzed. In particular, two fractions showed the highest biological activity as ACE inhibitors with IC50 at 0.158 and 0.134, thrombin inhibitors with IC50 of 167 and 155, and antioxidants in ABTS assay with SC50 at 1.375 and 0.992 mg/L, respectively. Further sequence analysis of the bioactive peptides was carried out using MALDI-TOF, which identified amino acid chains that have not been reported as bioactive so far. Bibliographic survey allowed identification of similarities between peptides reported in amaranth and other proteins. In conclusion, amaranth proteins are a potential source of peptides with multifunctional activity.

Bioactivity of Peptides Released During Lactic Fermentation of Amaranth Proteins with Potential Cardiovascular Protective Effect: An In Vitro Study.

Fermentation has shown to be an effective technique in bioactive peptides release. That is why in this study antihypertensive, antithrombotic, and antioxidant activity was evaluated during amaranth proteins fermentation with Lactobacillus casei Shirota and Streptococcus thermophilus 54102 in mono and combined culture. During fermentation an increase of free amine groups was observed, and no statistical differences among monocultures were shown, getting higher concentration in combined culture. This was related to antihypertensive and antioxidant activities, where the highest values were also found in the combined process (45% of angiotensin-converting enzyme inhibition, and 168 µmol Trolox equivalents per liter [TE/L] for 2,2-diphenyl-1-picrylhydrazyl, 268 µmol TE/L for 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid, and 381 µmol Fe2E/L for ferric reducing ability of plasma). On the contrary, antithrombotic activity was not related to free amine groups during fermentation, having the highest bioactivity in different moments in each experiment. L. casei Shirota and S. thermophilus 54102 are strains that are able to release bioactive peptides from amaranth protein, although amaranth is not a common matrix for the development of lactic acid bacteria. In addition, in this study it was observed for the first time that lactic acid strains are able to release bioactive peptides from amaranth protein. In addition, this methodology could be part for the development of fermented beverages, different from fermented milk, to diversify matrix to obtain a novel functional food.