Digestibility of Quinoa (Chenopodium quinoa Willd.) Protein Concentrate and Its Potential to Inhibit Lipid Peroxidation in the Zebrafish Larvae Model

Quinoa protein concentrate (QPC) was extracted and digested under in vitro gastrointestinal conditions. The protein content of QPC was in the range between 52.40 and 65.01% depending on the assay used. Quinoa proteins were almost completely hydrolyzed by pepsin at pH of 1.2, 2.0, and 3.2. At high pH, only partial hydrolysis was observed. During the duodenal phase, no intact proteins were visible, indicating their susceptibility to the in vitro simulated digestive conditions. Zebrafish larvae model was used to evaluate the in vivo ability of gastrointestinal digests to inhibit lipid peroxidation. Gastric digestion at pH 1.2 showed the highest lipid peroxidation inhibition percentage (75.15%). The lipid peroxidation activity increased after the duodenal phase. The digest obtained at the end of the digestive process showed an inhibition percentage of 82.10%, comparable to that showed when using BHT as positive control (87.13%).

Protein degradation and peptide release from milk proteins in human jejunum. Comparison with in vitro gastrointestinal simulation

Human jejunal digests after oral ingestion of casein and whey protein were collected by a nasogastric tube and protein degradation and peptide release was compared with that found in the digests of the same substrates using a standardised protocol. No intact casein was detected in the jejunal nor in the in vitro samples taken during the intestinal phase, while β-lactoglobulin was found in one hour-jejunal samples in agreement with the in vitro digestion. In vivo and in vitro digests showed comparable peptide profiles and high number of common sequences. A selective precipitation step was used to strengthen the identification of phosphorylated peptides. Most of the sequences found in jejunum, some of them not previously described, were also identified in the simulated digests. Common resistant regions to digestion were identified, revealing that the in vitro protocol constitutes a good approximation to the physiological gastrointestinal digestion of milk proteins.

Chemopreventive properties of Peptide Lunasin: a review

Cancer has become one the most common causes of death in developed countries and has been defined as the medical challenge of our times. Accumulating evidence support the notion that prevention can be a major component of cancer control. Chemoprevention, a relatively new and promising strategy to prevent cancer, is defined as the use of natural and/or synthetic substances to block, reverse, or retard the process of carcinogenesis. Plant-based foods, containing significant amounts of bioactive phytochemicals, may provide desiderable health benefits beyond basic nutrition to reduce the process of cancer. In the last few years, proteins and peptides have become one group of nutraceuticals that show potential results in preventing the different stages of cancer including initiation, promotion, and progression. Lunasin is a 43- amino acid peptide identified in soybean and other plants whose anti-carcinogenic activity has been demonstrated both in in vitro and in vivo assays. Moreover, this peptide has been found to exert anti-inflammatory and antioxidant properties that could contribute to its chemopreventive effects. Lunasin's bioactivity and its molecular mechanism(s) of actions are summarized in this review.

β-Lactoglobulin as source of bioactive peptides

Beta-lactoglobulin (beta-Lg) is currently an important source of biologically active peptides. These peptides are inactive within the sequence of the precursor protein, but they can be released by in vivo or in vitro enzymatic proteolysis. Once released, these peptides play important roles in the human health, including antihypertensive, antioxidant and antimicrobial activities as well as opioid-like features and ability to decrease the body-cholesterol levels. Bioactive peptides derived from beta-Lg are currently a point of intensive research. Their structure, biological significance and mechanism of action are briefly presented and discussed in this review.

Angiotensin-Converting Enzyme Inhibitory Activity of Peptides Derived from Caprine Kefir

In this study, a potent angiotensin-converting enzyme (ACE)-inhibitory activity was found in a commercial kefir made from caprine milk. The low molecular mass peptides released from caseins during fermentation were mainly responsible for this activity. Sixteen peptides were identified by HPLC-tandem mass spectrometry. Two of these peptides, with sequences PYVRYL and LVYPFTGPIPN, showed potent ACE-inhibitory properties. The impact of gastrointestinal digestion on ACE-inhibitory activity of kefir peptides was also evaluated. Some of these peptides were resistant to the incubation with pepsin followed by hydrolysis with Corolase PP. The ACE-inhibitory activity after simulated digestion was similar to or slightly lower than unhydrolyzed peptides, except for peptide beta-casein f(47-52) (DKIHPF), which exhibited an activity 8 times greater after hydrolysis.