Evaluation Of Anti-Hypertensive And Vasorelaxant Effects Of Phaleria Macrocarpa Extracts
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Date
2015-04
Authors
Altaf, Rabia
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Abstract
The present study investigated the anti-hypertensive effect of Phaleria macrocarpa
extracts in spontaneously hypertensive rats (SHR), Wistar Kyoto (WKY) rats and
the vasorelaxant effect of the extracts in isolated rat aorta of Sprague Dawley rats
using bioactivity guided approach. The dried fruits were extracted sequentially in
solvents with different polarity. The anti-hypertensive effect of the graded doses of
crude extracts was evaluated in SHR by non-invasive blood pressure method.
Petroleum ether (PE) and water extracts (WE) significantly reduced the blood
pressure on 14th day of treatment (15.9 and 27.7% respectively, p<0.05) suggesting
profound anti-hypertensive activity of these two extracts. WE reduced both the
mean arterial pressure (MAP) and heart rate (HR) in WKY by 16.3 and 4.3%
respectively (p<0.05). WE inhibited norepinephrine (NE) induced elevation of
MAP and HR in WKY with less effects against the pressor responses to
isoprenaline (p<0.05) suggesting its possible alpha-antagonistic and calcium
channel blocking effect. WE significantly inhibited MAP, HR and pulse wave
velocity (PWV) when compared with control group (p<0.05). An oral
administration of WE to SHR for 14 days significantly inhibited the plasma level of
angiotensin converting enzyme (p<0.05). Moreover, it elevated plasma nitric oxide
(NO) level with respect to control group (p<0.05) supporting its effect on PWV as
NO directly reduces the stiffness in arteries determined by the values of PWV. In the in vitro study, PE and WE inhibited NE induced contraction in rat aortic rings
by 40 and 58% respectively (p<0.05). The active WE fraction WF-4 showed
considerable vasorelaxant effect (42.8% relaxation, p<0.05). The sub-fraction SF-2
of WF-4 inhibited contraction in rat aorta up to 44.5% (p<0.05). SF-2 elicited
vasorelaxation in aortic rings with both denuded as well intact endothelium.
However, incubation of intact aortic rings with L-NAME and indomethacin
significantly blocked the vasorelaxant effect of SF-2, suggesting the involvement of
NO and prostacyclin pathway respectively. Moreover, SF-2 was found to exhibit its
vasorelaxant effect in denuded aortic rings pre-contracted with NE by inhibiting
calcium induced contraction in calcium free Kreb’s solution suggesting blockage of
calcium influx through receptor operated calcium channels (ROCC) (p<0.05).
When subjected to high performance liquid chromatography (HPLC) analysis, SF-2
was found to contain rutin, mangiferin and gallic acid (0.04%, 0.21% and 0.04%
respectively) in SF-2. This study supports the potential of use of Phaleria
macrocarpa extracts to treat hypertension in traditional medicine.
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