Research On Angiotensin Converting Enzyme Inhibitory Effect And Antioxidant Activity Of Hemp Seed(Cannabis Sativa L.)

Hypertension is a common chronic disease with increased arterial blood pressure as the main clinical symptom. Some undesirable side effects of synthetic drugs for hypertension have been reported. Therefore, to find safe, effective and innovative drugs is required to control the high blood pressure. Traditional Chinese medicine(TCM) has attracted particular attention due to their non-toxic nature(no side effects). The development of effective traditional Chinese medicine in lowering blood pressure and to research the mechanism and active ingredients are of great significance.According to the Chinese medical theory, the hemp seed has the antihypertensive effect. Scarce data has been reported on its active components and its mechanism of antihypertension, mainly on the inhibition effect of protein hydrolysate towards angiotensin-converting enzyme(ACE) and renin. The hemp seed is rich of polyunsaturated fatty acids(PUFA), which have roles in lowering blood pressure and are involved in the inhibition of ACE activity. In addition, it has been pointed out that hypertension is associated with the reactive oxygen species(ROS). In this thesis, the inhibition effect on ACE and its antioxidant activity of of the hemp seed(the protein hydrolysate and polyunsaturated fatty acids) in vitro were investigated, which will be helpful to understand its antihypertensive mechanism.The fatty acids constituents in the hemp seed oil was determined by gas chromatography-mass spectrometry, when purified by the method of urea inclusion. The factors that affect the separation, including the amount of solvent and urea, the crystal temperature and crystal time were discussed. With the optimal conditions, the purity of polyunsaturated fatty acids reached up to > 90%, while the yield was 31.3%.The ACE inhibitory activity of purified polyunsaturated fatty acids has been estimated. The IC50 values of standards of free fatty acids, oleic acid, linoleic acid and linolenic acid as well as the protein hydrolysate were evaluated. Both fatty acids and protein were proved to be active. The IC50(ACE) value of the polyunsaturated fatty acids is between those of inoleic acid and oleic acid. It indicates that these threekinds of fatty acids work together to inhibit the activity of ACE. Lineweaver–Burk plots revealed that the PUFA were uncompetitive inhibitor of ACE, which inhibited ACE via binding to ES.18 constituents(Xn, n= 1-18)were obtained after the different solvents extraction of the hemp seed, AB-8 macroporous resin and Sephadex LH-20 size exclusion chromatography. The regression equation was established to reproduce their scavenging ability of 2,2-Diphenyl-1-picrylhydrazyl(DPPH) radical with stepwise regression method. It indicated that the compounds corresponding to X12, X6 and X5 peaks are the main components with antioxidant activity.