Abstract:
Ginger (Zingiber officinale) and turmeric (Curcuma longa) rhizomes have been reportedly used in folk medicine for the treatment of hypertension, but the mechanism of action remains unexplored. Hence, this study investigated the effect of the rhizomes on some enzyme activities of renin-angiotensin, purinergic and cholinergic systems in hypertensive rats. Aqueous extracts of both rhizomes were prepared in distilled water (1:20 w/v). Subsequently, the ability of the extracts to inhibit some pro-oxidants (FeSO4 and Sodium nitroprusside) induced lipid peroxidation in rat heart was assessed in vitro. Then, the effect of the extracts on some key enzymes linked with hypertension [angiotensin-1-converting enzyme (ACE), arginase, acetylcholinesterase (AChE) and ectonucleotidase (NTPDase, 5'-nucleotidase and adenosine deaminase (ADA)] was also determined in vitro. Thereafter, the effect of dietary supplementation of both rhizomes in high cholesterol (2%) diet fed rats and Nω-Nitro-L-arginine-methylester (L-NAME) were evaluated. Thereafter, the physioactive phenolic constituents were characterized using high performance liquid chromatography (HPLC). The results revealed that both rhizomes exhibited antioxidant properties, inhibited ACE, arginase, and AChE activities as well as modulate ectonucleotidase activity in vitro. Furthermore, the rhizomes demonstrated anti-hypertensive properties by lowering systolic and diastolic blood pressures; inhibiting ACE, arginase, acetylcholinesterase and butyrylcholinesterase activities as well as modulate ectonucleotidase activity in L-NAME induce hypertensive rats. Also, they exhibited hypocholesterolemic (cholesterol-lowering) properties in high cholesterol diet fed rats by preventing alterations in the lipid profile [total cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol and very low-density lipoprotein (VLDL) cholesterol], level of lipid peroxidation, arginase and ACE activities. Therefore, the antioxidant capacity, hypocholesterolemic properties and inhibitory/modulatory
iii
effect on enzyme activities of renin-angiotensin (ACE), purinergic (ectonucleotidase [NTPDase, 5-nucleotidase and ADA]) and cholinergic (AChE and BuCHE) systems could further buttress their antihypertensive benefits in folk medicine. However, these activities may be directly/indirectly attributed to the phenolic constituents.
