No abstract

Antithrombotic activity of brewers' spent grain peptides before and after simulated gastrointestinal digestion and their effects on blood coagulation pathways were evaluated. Two hydrolysates were produced using sequential enzymatic systems: alkaline protease + Flavourzyme (AF) and neutral protease + Flavourzyme (PF). Simulation of gastrointestinal digestion of AF and PF hydrolysates was made using porcine pepsin and pancreatin enzymes, obtaining the corresponding digested samples: AFD and PFD, respectively. Peptides were fractionated by ultrafiltration using a 1 kDa cut-off membrane. Hydrolysates had peptides with medium and low molecular weights (2100 and 500 Da, respectively), and Glu, Asp, Leu, Ala, and Phe were the most abundant amino acids. Gastrointestinal digested hydrolysates presented high proportion of small peptides (~500 Da), and higher amount of Val, Tyr, and Phe than hydrolysates. Mass spectrum (HDMS Q-TOF) of AFD-ultrafiltered fraction <1 kDa exhibited peptides from 500 to 1000 Da, which are not present in AF. PFD showed the generation of new peptides from 430 to 1070 Da. All samples showed thrombin inhibitory activity. However, no effect was observed on prothrombin time. Peptides <1 kDa from hydrolysates and digested samples delayed thrombin and thromboplastin time respect to the control (~63%). Also the samples showed thrombin inhibitory activity at common pathway level. Thus, brewers' spent grain peptides exerted their antithrombotic activity by inhibiting the intrinsic and common pathways of blood coagulation. This is the first report to demonstrate that brewers' spent grain peptides are able to delay clotting time after simulated gastrointestinal digestion.

The aim of this work was to evaluate copper-chelating, iron-chelating and anticariogenic activity of peptides obtained by enzymatic hydrolysis of P. columbina protein concentrate and to study the effects of chelating peptides on iron bio-accessibility. Two hydrolyzates were obtained from P. columbina protein concentrate (PC) using two hydrolysis systems: alkaline protease (A) and alkaline protease + Flavourzyme (AF). FPLC gel filtration profile of PC shows a peak having molecular weight (MW) higher than 7000 Da (proteins). A and AF hydrolyzates had peptides with medium and low MW (1013 and 270 Da), respectively. Additionally, AF presented free amino acids with MW around 82 Da and higher content of His and Ser. Peptides from AF showed the highest chelating properties measured as copper-chelating activity (the lowest β-carotene oxidation rate: Ro; 0.7 min(-1)), iron-chelating activity (33%), and phosphorous and Ca(2+) release inhibition (87 and 81%, respectively). These properties could indicate antioxidant properties, promotion of iron absorption and anticariogenic activity, respectively. In fact, hydrolyzates promoted iron dialyzability (≈ 16%), values being higher than that found for P. columbina seaweed. Chelating peptides from both hydrolyzates can maintain the iron in a soluble and bio-accessible form after gastrointestinal digestion.