Ajuga
bracteosa
has been
used in
traditional medicine to treat hypertension and other ailments. The
present study has been designed to investigate the beneficial effects
of
A. bracteosa
in
l
-nitro
arginine methyl ester (
l
-NAME)-induced hypertensive rats.
Hypertension was induced by intraperitoneal injection of
l
-NAME (185 μmol kg
–1
i.p.). The aqueous methanol
extract of
A. bracteosa
(AMEAB, 250
and 500 mg kg
–1
) and coumarin (30 and 70 mg kg
–1
) were administered orally from day 8 to day 35 of
the study.
In vivo
antihypertensive activity was
assessed by measuring the blood pressure using a PowerLab data system.
The effects of the AMEAB and coumarin on nitric oxide (NO), cyclic
guanosine monophosphate (cGMP), interleukin-6 (IL-6), the tumor necrosis
factor (TNF-α), and oxidative stress markers were also assessed
using kit methods. Phytochemical profiling of the AMEAB was carried
out through high-performance liquid chromatography (HPLC) where quercetin,
gallic acid, caffeic acid, vanillic acid, benzoic acid, syringic acid,
p
-coumaric acid, and ferulic acid were labeled as plant
constituents including coumarin. The AMEAB and coumarin significantly
reduced blood pressure at the tested doses of 500 and 70 mg kg
–1
, respectively. Serum levels of NO and cGMP were found
to be significantly increased in AMEAB- and coumarin-treated groups
when compared with only
l
-NAME-challenged rats. In addition,
a marked decrease was noticed in the serum concentrations of proinflammatory
cytokines (IL-6 and TNF-α) in AMEAB- and coumarin-treated rats.
Moreover, in AMEAB- and coumarin-treated animals, a noticeable improvement
was observed in the levels of antioxidant enzymes including catalase,
superoxide dismutase, and malonaldehyde, and the total oxidant status
when compared with those of only
l
-NAME-challenged rats.
The data of real-time polymerase chain reaction (RT-PCR) experiments
supported that the antihypertensive and anti-inflammatory activities
of the AMEAB and coumarin are possibly mediated through modulation
of endothelial nitric oxide synthase (eNOS), angiotensin-converting
enzyme (ACE), nuclear factor (NF)-kB, and COX-2 gene expressions.
This study concludes that
A. bracteosa
possesses an antihypertensive effect mediated through the modulation
of the antioxidant, anti-inflammatory, and NO/cGMP pathways, thus
providing a rationale to the antihypertensive use of
A. bracteosa
in traditional medicine.