Pharmacological Evaluation On The Effect Of Syzygium Polyanthum (Wight) Walp. Leaves Extract On Rat’s Blood Pressure And Related Parameters
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Date
2015-07
Authors
Ismail, Azlini
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
Syzygium polyanthum (Wight) Walp. var. Polyanthum leaves are
traditionally consumed by the Malays as an alternative treatment for hypertension.
However, the scientific evidence to support this claim is scarcely reported. The
present study investigated the effects of aqueous (AESP) and residual methanolic
extracts (met-AESP) of S. polyanthum leaves on rat’s blood pressure and related
parameters. Both extracts were orally administered on Wistar-Kyoto (WKY) and
Spontaneously Hypertensive rats (SHR), then systolic blood pressure (SBP) were
monitored within 24 hours. Later, both extracts were daily administered via oral
administration for 3 weeks in SHR, then the SBP were monitored within 3 weeks. In
the subsequent study, both extracts were intravenously administered in anaesthetized
WKY and SHR, then, mean arterial, systolic, and diastolic blood pressures, as well
as the heart rate were recorded within 20 minutes. In the following study, both
extracts were added on the phenylephrine (1 μM) - and serotonin (10 μM)-
contracted isolated thoracic aorta rings from WKY and SHR. Possible involvement
of autonomic receptors and nitric oxide in mediating the blood pressure reduction
and vasorelaxation by both extracts was investigated by using respective blockers
for nicotinic-and muscarinic-acetylcholine, α- and β-adrenergic receptors, and nitric
oxide. Phytochemical screening, gas chromatography mass spectrometry, and high
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performance liquid chromatography were carried out to obtain phytochemical profiles of the extracts. The orally-administered extracts, either as an acute dose or repeated-dose significantly reduced blood pressure of conscious SHR. Both extracts showed significant hypotensive effects after 3-week treatment, but the onset of hypotensive effect by met-AESP was faster than AESP. Both of the intravenously-administered extracts caused significant reduction in blood pressure, but only AESP at the highest dose caused mild reduction in heart rate of anaesthetized WKY and SHR. The blood pressure reduction by met-AESP was more sustained than AESP in anaesthetized SHR. Both extracts also caused vasorelaxation on aorta rings from WKY and SHR with comparable effects. The reductions in blood pressure and heart rate, and also vasorelaxation by AESP, were suggested to partly involve α-adrenergic receptors, while the reduction in blood pressure and vasorelaxation by met-AESP partly involved muscarinic-acetylcholine and β-adrenergic receptors. A part of the reduction in blood pressure and the vasorelaxation effects by both extracts possibly involve nitric oxide. AESP contained phenolics, tannins, flavonoids, saponins, and cardiac glycosides; while met-AESP contained phenolics, tannins, flavonoids, terpenoids, and resins. Glycerine, acetic acid, and gallic acid were the potential compounds in AESP, while seselin, linoleic acid, methyl hexadecanoate, oleic acid, and gallic acid were the potential compounds in met-AESP that possibly contributed to the reduction in blood pressure and vasorelaxation by these extracts. In conclusion, this study supported the traditional use of S. polyanthum leaves extracts as an alternative treatment for hypertension.
Description
Keywords
Syzygium polyanthum , alternative treatment for hypertension.