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Umami peptides can help reduce the salt content in foods while still maintaining a savory taste. Few studies have reported the bioactivity of umami peptides after consumption. We studied the bioactivities of 12 umami peptides after gastrointestinal digestion. Three umami peptides exhibited angiotensin I-converting enzyme (ACE) inhibitory and antioxidant activity after digestion. Six novel peptides were identified from digestion solutions of the peptides by HPLC-MS/MS. Among them, CC, CCNK, and HCHT had both ACE inhibitory activity (IC50 values were 9.81, 9.00, and 114.99 μM, respectively) and antioxidant activity (strong 1,1-Diphenyl-2-pycryl-hydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical scavenging activities). AHSVRF had strong ACE inhibitory activity. These peptides increased the nitric oxide concentration and decreased the content of endothelin-1 in a medium of human umbilical vein endothelial cells in a dose-dependent manner. Experiments with damaged HepG2 cells showed that peptides CC, CCNK, and HCHT had antioxidant activity through their cytoprotective effects and by reducing the reactive oxygen species content. The results indicated that umami peptides may provide many health benefits after consumption.

Broccoli-derived peptides show beneficial metabolic effects, and it is necessary to examine their exact functional sequences. First, peptides from the trypsin hydrolysate of broccoli proteins were isolated and identified using column chromatography and quadrupole time-of-flight mass spectrometry. After that, their functions were verified by oral administration. The results identified two novel peptides as Leu-Pro-Gly-Val-Leu-Pro-Val-Ala (LPGVLPVA) and Tyr-Leu-Tyr-Ser-Pro-Ala-Tyr (YLYSPAY). LPGVLPVA exhibited an ACE IC50 value of 0.776 ± 0.03 μM and a DPP-IV IC50 value of 392 ± 24 μM; YLYSPAY showed an ACE IC50 value of 8.52 ± 0.63 μM and a DPP-IV IC50 value of 181 ± 4 μM. Administration of the peptides reduced the blood pressure of spontaneously hypertensive rats and reduced blood glucose levels in the oral glucose tolerance test in mice. The results indicated that LPGVLPVA and YLYSPAY could be potential nutritional candidates for hypertensive and diabetic people, especially for those with diabetes associated with hypertension.

The angiotensin-converting enzyme (ACE) inhibitory peptide LVLPGE provides outstanding antihypertensive effects in vivo, with a maximum systolic blood pressure (SBP) drop of 39 mmHg at a dose of 10 mg/kg. We evaluated the gastrointestinal digestion, transport, and in vivo antihypertensive effects of LVLPGE at different doses. LVLPGE was resistant to gastrointestinal enzymes with a stability of 97.8% and a permeability Papp of (5.09 ± 0.94) × 10-7 cm/s. LVLPGE was mainly transported through the Caco-2 cell monolayer by the peptide transporter PepT 1 and passive-mediated transport. LVLPGE at doses of 30 and 50 mg/kg had a positive antihypertensive effect in vivo; 30 mg/kg had a more significant effect than 50 mg/kg. After oral administration, the pharmacokinetics of LVLPGE showed that the Cmax was 4.65 ng/mL at 2 min. The blood pressure-lowering effect increased as the concentration of LVLPGE increased in the plasma of spontaneous hypertensive rats (SHRs).

In the present study we purified and identified peptides from broccoli protein hydrolysates and evaluated their angiotensin-converting enzyme (ACE) inhibitory activity in vitro and hypotensive effect in vivo. Three ACE inhibitory peptides were isolated and identified as IPPAYTK, LVLPGELAK, and TFQGPPHGIQVER, and their inhibitory IC50 values were 23.5, 184.0, and 3.4 μM, respectively. We then investigated the effect of gastrointestinal digestion on ACE inhibitory activity. We detected almost two times the ACE inhibitory activity of the peptide LVLPGELAK following simulated digestion than prior to digestion. LVLPGE and LAK, two novel peptides exhibiting high ACE inhibitory activity, were discovered following digestion and possessed IC50 values of 13.5 and 48.0 μM, respectively. The hypotensive effect of the peptides was assessed after oral administration to spontaneous hypertensive rats (SHRs). We found that LVLPGE and LAK demonstrated a significant hypotensive effect in vivo. Protein from broccoli may thus constitute a potential antihypertensive peptide source.