AIM OF THE STUDY: This study is designed to investigate the vasorelaxation effect of G. uralensis from various extracts and to study its pharmacology effect.
MATERIALS AND METHODS: The vasorelaxation effect of G. uralensis extracts were evaluated on thoracic aortic rings isolated from Sprague Dawley rats.
RESULTS: Among these three extracts of G. uralensis, 50% ethanolic extract (EFG) showed the strongest vasorelaxation activity. EFG caused the relaxation of the aortic rings pre-contracted with phenylephrine either in the presence or absence of endothelium and pre-contracted with potassium chloride in endothelium-intact aortic ring. Nω-nitro-L-arginine methyl ester, methylene blue, or 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one inhibit the vasorelaxation effect of EFG in the presence of endothelium. On the other hand, in the presence of the potassium channel blockers (tetraethylammonium and barium chloride), the vasorelaxation effect of EFG was not affected, but glibenclamide and 4-aminopyridine did inhibit the vasorelaxation effect of EFG. With indomethacin, atropine and propranolol, the vasorelaxation effect by EFG was significantly reduced. EFG was also found to be effective in reducing Ca(2+) release from sarcoplasmic reticulum and the blocking of calcium channels.
CONCLUSIONS: The results obtained suggest that EFG is involved in the NO/sGC/cGMP pathway.
METHODS: Adult male Sprague-Dawley rats were divided into 11 groups; the control group was fed with rat chow, and the other groups were fed with chow that was mixed with 15% weight/weight palm or soy oils, which were either in a fresh form or heated once, twice, five, or ten times. Blood pressures were measured at the baseline and throughout the 24-week study. Plasma nitric oxide levels were assessed prior to treatment and at the end of the study. Following 24 weeks, the rats were sacrificed to investigate their vascular reactivity using the thoracic aorta.
RESULTS: Palm and soy oils had no detrimental effects on blood pressure, and they significantly elevated the nitric oxide contents and reduced the contractile responses to phenylephrine. However, trials using palm and soy oils that were repeatedly heated showed an increase in blood pressure, enhanced phenylephrine-induced contractions, reduced acetylcholine- and sodium nitroprusside-induced relaxations relative to the control and rats that were fed fresh vegetable oils.
CONCLUSIONS: The blood pressure-raising effect of the heated vegetable cooking oils is associated with increased vascular reactivity and a reduction in nitric oxide levels. The chronic consumption of heated vegetable oils leads to disturbances in endogenous vascular regulatory substances, such as nitric oxide. The thermal oxidation of the cooking oils promotes the generation of free radicals and may play an important contributory role in the pathogenesis of hypertension in rats.
AIM OF THE STUDY: Chemico-biological standardization with respect to its vasorelaxation potential is the main objective of the present study. To investigate the vasorelaxation potential of key phytochemical of KGR, i.e., ethyl-p-methoxycinnamate (EPMC) and to study it's the mechanism of action.
MATERIALS AND METHODS: A HPLC method was developed and validated for the quality assessment of KGR using its two major phytochemicals i.e. ethyl-p-methoxycinnamate (EPMC) and ethyl cinnamate (EC) in KGR. The vasorelaxation effect of major phytochemicals of KGR was evaluated on the main mesenteric arteries isolated from male Wistar rats. Specific BKca channel blocker tetraethylammonium (TEA), receptor antagonist, nitric oxide scavenging capacity, and antioxidant potential were also evaluated for its plausible mechanism.
RESULTS: Present validated HPLC method facilitates simultaneous quantitation of EPMC and EC faster than classical GC techniques. EPMC has shown a dose-dependent relaxation in rat main mesenteric arteries (MMA) contracted by U46619 with an Emax of 58.68 ± 3.31%. Similarly, in endothelium-denuded MMA rings, relaxation was also observed (Emax of 61.83 ± 3.38%). Moreover, relaxation response to EPMC has strongly inhibited (Emax 14.76 ± 2.29%) when the tissue exposed to depolarizing high K+ containing buffer for the contraction. The point correlation dimension (pD2) values were also significantly decreased in high K+ treated arterial rings compared to control. Interestingly, when MMA rings incubated with a specific BKca channel blocker (TEA, 1 mM), the relaxation response to EPMC was also significantly blocked.
CONCLUSIONS: The first time this study demonstrated the chemical standardization of K. galanga rhizome and EPMC is responsible for its vasorelaxation potential as demonstrated by the endothelium-independent response mediated by Ca2+ dependent potassium channels.