Kinetics of Enzyme Inhibition and Antihypertensive Effects of Hemp Seed (<Emphasis Type="Italic">Cannabis sativa</Emphasis> L.) Protein Hydrolysates

The aim of this study was to determine the antihypertensive effects of enzymatic hemp seed protein hydrolysate (HPH) and its peptide fractions. Hemp seed protein isolate was digested by the sequential action of pepsin and pancreatin to mimic gastrointestinal digestion in human beings. The resultant HPH was separated by membrane ultrafiltration into peptide fractions with different sizes (<1 and 1–3 kDa). The HPH led to significantly higher (P < 0.05) in vitro inhibition of the activities of angiotensin I-converting enzyme (ACE) and renin, the two main enzymes involved in abnormal blood pressure elevation (hypertension). Kinetic studies showed that HPH and peptide fractions inhibited renin and ACE activities in a mixed-type pattern, indicating binding to areas other than the active site. Oral administration of HPH (200 mg/kg body weight) to spontaneously hypertensive rats led to significant reductions (P < 0.05) in systolic blood pressure (SBP) that reached a maximum of −30 mmHg after 8 h. In contrast, the hypotensive effects of peptide fractions (<1 and 1–3 kDa) had a maximum value of about −15 mmHg after 6–8 h post oral administration. The results suggest a synergistic antihypertensive effect of the peptides present within HPH; this effect was reduced significantly (P < 0.05) upon separation into peptide fractions.