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- Nigella (Black Cumin; Nigella sativa)
- Hypertension
- Oxidative Stress
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Date:
04-30-2013 | HC# 041351-471
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Re: Potential Role of Nigella in Prevention and Control of Hypertension
Leong
X-F, Mustafa MR, Jaarin K. Nigella sativa
and its protective role in oxidative stress and hypertension. Evid Based Complement Altern Med. 2013;2013:120732.
doi: 10.1155/2013/120732.
Nigella
(black cumin; Nigella sativa), also
known by its Arabic name habat-ul sauda
or habbatussauda, has been used for
centuries medicinally and as a food spice throughout the Middle East, India,
and Northern Africa. It is an annual flowering plant with pale blue flowers and
has fruit with black, angular seeds. The seeds are used for treating diabetes, hypertension,
hypercholesterolemia, inflammation, and gastrointestinal disorders. The purpose
of this article was to review the literature evaluating the antihypertensive effect
of nigella.
The
seed oil is rich in polyphenols and tocopherols. The seeds contain 36-38% fixed
oils (mainly fatty acids: linoleic [C18:2], oleic [C18:1], palmitic [C16:0], and
stearic [C18:0] acids), 0.4-2.5% essential (volatile) oil, proteins, alkaloids,
saponins, and 30-48% thymoquinone along with its derivatives dithymoquinone,
thymohydroquinone, and thymol. Thymoquinone is the most pharmacologically
active ingredient in abundance in the seeds.
The
seed oil has strong antioxidant properties. In particular, thymoquinone is a potent
superoxide radical scavenger which is as effective as superoxide dismutase (SOD)
against superoxides generated either photochemically, biochemically, or derived
from calcium ionophore. Thymoquinone has a strong protective effect by decreasing
oxidative stress through preserving glutathione and increasing the levels and
activities of antioxidant enzymes like SOD and glutathione peroxidase.
Oxidative
stress may play an important role in hypertension pathogenesis by enhancing
sequestration of nitric oxide (NO) by reactive oxygen species (ROS), forming
lipid peroxidation products, and depleting nitric oxide synthase (NOS) cofactor
tetrahydrobiopterin. NO causes vasodilation that reduces peripheral resistance,
thus decreasing blood pressure, so its lower bioavailability may result in
endothelial dysfunction. Also, oxidative stress may cause functional and
structural damage in the molecules and cells of the vascular wall and blood
vessels. Therefore, nigella may protect against hypertension via its
antioxidant abilities. However, more research is needed to test this
hypothesis.
Hypertension
may be reduced by a cardiac depressant effect, calcium channel blockage, and a diuretic
effect. Studies show that nigella volatile oil and thymoquinone decreased
arterial blood pressure and heart rate in rats, which was mainly mediated
centrally, either directly or indirectly, via serotoninergic and muscarinic receptors.
Also in rats, the cardiac depressant effects of nigella may be mediated by
nicotinic receptors. Overall, the cardiac depressant and hypotensive effects of
nigella may be centrally mediated, involving the vasomotor center of the
medulla and sympathetic outflow to the periphery. Thymol has been shown to dose-dependently
reduce blood pressure by inhibiting calcium ion channels. When calcium channels
are blocked, vasorelaxation increases. Kidney function is important for the
control and pathogenesis of hypertension. Nigella may decrease blood pressure
via a diuretic action; it increased urinary excretion of sodium, potassium,
chloride, and urea. It also increased glomerular filtration rate and urinary
and electrolyte output, independent of the renin-angiotensin-aldosterone
system.
One
study in patients with mild hypertension revealed that oral nigella seed
extract of 100 mg/day or 200 mg/day for eight weeks significantly and
dose-dependently reduced diastolic and systolic blood pressure compared with
placebo and baseline (P<0.01 for all; except
systolic blood pressure with 100 mg/day, P=0.03). There were also
significant decreases in total cholesterol and low-density lipoprotein (LDL)
cholesterol (P<0.01 for both), and no adverse effects.1
The
authors conclude that nigella may have cardiovascular protective effects via a
multitude of actions. They state that nigella has been used in traditional
medicine with no reported adverse events. The authors only include one clinical
study assessing the effect of nigella seed extract in patients with
hypertension. A quick search of PubMed revealed that there are only two clinical
trials available for this indication. More studies in humans are needed to
confirm efficacy.
—Heather S. Oliff,
PhD
Reference
1Oppel M. Study finds
nigella seed extract may help lower mild high blood pressure as well as total
and LDL cholesterol levels. HerbClip.
May 15, 2009 (No. 120682-376). Austin, TX: American Botanical Council. Review
of Antihypertensive effect of Nigella
sativa seed extract in patients with mild hypertension by Dehkordi FR,
Kamkhah AF. Fundam Clin Pharmacol.
August 2008;22(4):447-452.
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