Ramli, Nurul Syahida
(2021)
Evaluation of aqueous extract of syzygium polyanthum leaves as anti-hypertensive agent in spontaneous hypertensive rat (SHR).
PhD thesis, Universiti Sains Malaysia.
Abstract
Hypertension is associated with significant morbidity and mortality. The use
of medicinal herbs as alternative medicines to manage hypertension is increasing
exponentially. Syzygium polyanthum, has been claimed traditionally as an
antihypertensive agent. This study aimed to determine the antihypertensive effects of
the aqueous extract of S. polyanthum (AESP) leaves and its mechanisms using
spontaneously hypertensive rats (SHR). The phytochemical profiling, antioxidant
properties and antihypertensive activity were evaluated. Fifty male SHR were divided
equally into 5 groups; untreated-SHR, Losartan-treated, 3 groups of AESP-treated
with different dosages (1500 mg/kg, 1750 mg/kg and 2250 mg/kg), and 10 male WKY
rats as control. All treatments were given orally for 12th weeks. Systolic blood pressure
(SBP) was measured biweekly. Whereas, the biochemical analysis, oxidative stress
markers and angiotensin-converting enzyme (ACE) level were evaluated at the end of
the study. The histology of thoracic aorta and kidney were assessed using
haematoxylin & eosin (H&E) staining, and scanning electron microscope (SEM).
AESP contains flavonoids and phenols with gallic acid detected. AESP showed high
in vitro antioxidant and ACE-inhibitory activities. In AESP-treated SHR; SBP reduced
significantly, improved renal function and oxidative stress markers. However, only
AESP (2250 mg/kg) significantly reduced ACE concentration. There was also
histology improvement of the thoracic aorta and renal in AESP-treated SHR. Hence,
the study suggests that antihypertensive properties of AESP are due to its antioxidant(mainly gallic acid) and ACE inhibitory activity. Thus, this study reveals the
antihypertensive mechanism of AESP exerted inhibitory activity through suppression
of the ACE action which might involved RAAS pathway.
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