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The Guardian, Nigeria
IT is blamed for the rising cases of strokes, heart attacks, heart failure, atherosclerosis (hardening of arteries), blindness, arterial aneurysm, and chronic kidney failure in the country.
Several studies have shown that moderate elevation of arterial Blood Pressure (BP) or rather hypertension leads to shortened life expectancy.
However, a recent review of natural herbs used in the treatment of hypertension has provided an introduction of the naturally occurring medicinal plants that have so far been scientifically studied and reported to have hypotensive or antihypertensive effects.
The study published in Pharmacognosy Review is titled “Role of natural herbs in the treatment of hypertension.”
According to the study, naturally occurring medicinal plants, herbs having hypotensive/antihypertensive potential include among others: garlic (Allium sativum), buchu (Agathosma betulina), soursop/graviola (Annona muricata), celery (Apium graveolens), breadfruit (Artocarpus altilis), green oat (Avena sativa), tea (Camellia sinensis), stinging weed/coffee weed (Cassia occidentalis), carrot (Daucus carota).
Other herbs for treating hypertension according to the Pharmacognosy Review study are: soybean (Glycine max), zobo/roselle (Hibiscus sabdariffa), stonebreaker (Lepidium latifolium), tomato (Lycopersicon esculentum), Moringa oleiferia, scent leaf/basil (Ocimum basilicum), Phyllanthus amarus (ngwu in Ibo), ginger (Zingiber officinale), sesame (Sesamum indicum).
Phyllanthus amarus belongs to the plant family Euphorbiaceae. To the Efik it is called oyomokeso amanke edem; geeron-tsuntsaayee (birds millet) in Hausa; Ibo (Asaba) buchi oro, Ibo (Umuahia) ngwu; iyeke in Urhobo; and ehin olobe or eyin olobe in Yoruba.
In another published study featured in the Journal of Medicine, it was revealed that common spices can protect from heart disease and the deterioration brought about by aging. In the said study, researchers discovered a connection between the phenol content of certain herbs and spices and their capacity to prevent glycation and formation of AGE compounds that are responsible for premature aging and heart disease.
Also, according to the study, “An Ethnobotanical Survey of Herbal Markets and Medicinal Plants in Lagos State of Nigeria” published in Ethnobotanical Leaflets by researchers from the Department of Botany and Microbiology, University of Lagos, herbal cures for hypertension include: leaves of Persea Americana (avocado) are made into shreds, dried and taken as infusion; leaves of Senecio biafrae (worowo in Yoruba or Sierra Leone bologna) added to fermented seeds of Parkia biglobosa (dawadawa in Hausa, African locust beans in English, Igba/Iyere in Yoruba, and Nere in Bambara) are used to prepare soup which is eaten; leaves of Talinum triangulare (water leaf) or Basella alba (Indian spinach in English, Amunututu in Yoruba) may also be used; and kola nut’s mistletoe mixed with honey is also effective.
Another study titled “Phytochemical Analysis of Medicinal Plants Used for the Management of Hypertension by Esan people of Edo State, Nigeria” and published in Ethnobotanical Leaflets by researchers from Ambrose Alli University, Ekpoma, Edo State, identified 14 endemic plant species distributed in 12 taxonomic families commonly used to manage hypertension.
They include: guava (Psidium guajava), West African black pepper/Ashanti pepper (Piper guineense, Uziza in Igbo and Ata iyere in Yoruba), mistletoe (Loranthus spectobulus), water leaf (Talinum triangulare), Nigerian senna/negro coffee (Senna occidentalis), serpent wood or swizzler stick (Rauwolfia vomitoria), garlic (Allium sativum), onions (Allium cepa), pawpaw (Carica papaya), asthma herb (Euphorbia hirta), scent leaf/basil (Ocimum gratissimum), avocado (Persea americana), cow-foot (Peperomia pellucida), and bitter leaf (Vernonia amygdalina).
Method of preparation:
The bulbs of garlic are blended with honey for the purpose of hypertension. The unripe rind of pawpaw is peeled and soaked in water and after three days, a cup is taken daily. The leaves are also used for treating hypertension.
Leaves of avocado pear are cut into pieces, dried and made into tea, for the management of hypertension. The cotyledons of avocado pear seed are cut into pieces, dried and grinded into powder. A dessert spoonful in 200ml hot water taken after meals gives relieve for the ailment.
Guava leaves are soaked in salt water, washed and squeezed and product made up with fresh water to give a greenish liquid that is taken, one glass two times daily for one week to increase blood level and offer protection against heart attack.
Also, the fresh leaves of bitter are chewed and swallowed or ground, or stirred in water, and the liquid taken, to manage hypertension.
Garlic has long been used for a variety of cardiovascular conditions, especially hyperlipidemia. It has also been reported to have hypotensive action. It is thought to increase nitric oxide production, resulting in smooth muscle relaxation and vasodilatation. One of the primary active compounds that gives garlic its characteristic odor and many of its healing benefits is called allicin.
Meta-analysis of randomly chosen literary data has demonstrated that garlic is related to decrease of BP in patients with increased systolic pressure, but not in patients without increased systolic pressure.
Garlic preparations have been found to be superior to placebo in reducing BP in individuals with hypertension. The antioxidative and antihypertensive effect of garlic has been observed in 20 patients with hypertension compared to 20 patients with normal pressure, who have been receiving garlic pearls preparation for a period of two months.
The results have revealed decreased BP, significant reduction of 8-hydroxy-2-deoxyguanosin, level of nitric oxide, and lipid peroxidation, and an increased level of antioxidative vitamins (C and E). This study points to the beneficial cardioprotective action of garlic in essential hypertension.
In a pilot study made at Clinical Research Center of New Orleans, United States, on whether garlic could lower blood pressure, nine patients with severe hypertension were given a garlic preparation containing 1.3 per cent allicin. Sitting blood pressure fell with a significant decrease in diastolic blood pressure only five to 14 hours after the dose. Moreover, it was proven in a 2009 study that fresh garlic has more potent cardio-protective properties than processed garlic.
Annona muricata is a member of the family of custard apple trees called Annonaceae and a species of the genus Annona, known mostly for its edible fruits Annona. The tree grows natively in the Caribbean and Central America. The leaf extract of the plant has been reported to lower an elevated BP by decreasing the peripheral vascular resistance.
The plant is native to the Malay Peninsula and western Pacific islands. A study has shown that the leaf extract of the plant decreased the tension of phenylephrine-stimulated isolated guinea pig aorta rings by 15 to 35 per cent.
It has been used in traditional medicine to treat hypertension. Activity-directed fractionation of aerial parts of D. carota resulted in the isolation of two coumarin glycosides coded as DC-2 and DC-3. Intravenous administration of these compounds caused a dose-dependent (1–10 mg/kg) fall in arterial BP in NMT anesthetized rats. In the in vitro studies, both compounds caused a dose-dependent (10–200 ?g/ml) inhibitory effect on spontaneously beating guinea pig atria as well as on the K+ -induced contractions of rabbit aorta at similar concentrations.
These results indicate that DC-2 and DC-3 may be acting through blockade of calcium channels, and this effect may be responsible for the BP-lowering effect of the compounds observed in the in vivo studies. Two new guaiane-type sesquiterpene terpenoids containing an interesting epoxy unit, daucuside and daucusol, have been isolated from fruits of D. carota.
This happens to be one of the most extensively studied plants for antihypertensive properties. The leaves, calyx, and corolla of this plant are used traditionally in many West African countries for various medicinal purposes and as edibles. The antihypertensive effect of this plant extract has been variously studied. One study reported the antihypertensive effect of calyx of HS.
A similar result was independently produced in Lagos, Nigeria by Adegunloye et al. An intravenous administration of 20 mg/kg of a water extract of dry HS calyx produced a fall in the BP of experimentally induced hypertensive rats.
The antihypertensive effects of the crude extract of the HS have been attributed to mediation through acetylcholine and histamine like dependent mechanism through direct vasorelaxant effects.
Earlier report showed that the petal crude extract of same plant had a direct relaxant effect on the aortic smooth muscle of rats. The chronic administration of aqueous extract of HS has been reported to reverse cardiac hypertrophy in renovascular hypertensive rats.
Clinical trials of the plant extract in human being have shown reliable evidence of antihypertensive effects. A standardized dose of HS (9.6 mg per day) given to 39 patients and captopril, 50 mg per day, given to the same number of patients did not show significant difference relative to hypotensive effects, antihypertensive effectiveness and tolerability.
Tomato extract contains carotenoids, such as lycopene, beta carotene, and vitamin E, which are known as effective antioxidants, to inactivate free radicals and to slow the progress of atherosclerosis. A study showed that extract of tomato (Lyc-O-Mato) modestly reduces BP in patients with mild, untreated hypertension.
A significant correlation has been observed between systolic BP and lycopene levels. Tomato extract when added to patients treated with low doses of ACE inhibition, calcium channel blockers, or their combination with low-dose diuretics had a clinically significant effect-reduction of BP by more than 10 mmHg systolic and more than 5 mmHg diastolic pressure. No side effects to treatment were recorded and the compliance with treatment was high.
It has been reported that a crude extract of O. basilicum causes a fall in systolic, diastolic, and mean BP in a dose-dependent manner with median effective dose of 30 mg/kg. The antihypertensive effect is brief and returns to normal within two minutes. This cardiovascular effect of the extract has been attributed to eugenol, which exerts its effect by blocking the calcium channels.
Ginger root is commonly used in Asian cooking. It acts to improve blood circulation and relaxes muscles surrounding blood vessels. The crude extract of ginger (Zo.Cr) induced a dose-dependent (0.3-3 mg/kg) fall in the arterial BP of anesthetized rats. In guinea pig paired atria, Zo.Cr exhibited a cardiodepressant activity on the rate and force of spontaneous contractions.
In rabbit thoracic aorta preparation, Zo.Cr relaxed the phenyl ephrine-induced vascular contraction at a dose ten times higher than that required against K+ (80 mM)-induced contraction. Ca2+ channel-blocking activity was confirmed when Zo.Cr shifted the Ca2+ dose-response curves to the right, similar to the effect of verapamil. These data indicate that the BP-lowering effect of ginger is mediated through blockade of voltage-dependent calcium channels.
Chronic administration of Pet ether extract (PE) (50 mg/kg/day; po), toluene fraction (10 mg/kg/day; po) of ginger rhizome, and Korean ginseng extract (KGE) (30 mg/kg/day; po) significantly reduced the BP in deoxycorticosterone acetate salt-induced hypertensive rats, whereas PE (50 mg/kg/day; po) and KGE (30 mg/kg/day; po) reduced the BP in fructose-induced hypertensive rats. The mechanism of action may partly involve the serotonergic antagonistic property. Human trials for hypotensive effect of ginger have been few and generally used a low dose with inconclusive results.
Onions contain quercetin, an antioxidant flavonol found to prevent heart disease and stroke. In a research study published in the Journal of Nutrition, subjects with hypertension experienced a decrease in their blood pressure by 7mmHg systolic and 5 mmHg diastolic as opposed to those who were taking placebo.
This herb is a significant part of the Mediterranean diet, recognized to be one of the healthiest in the world. Oil made from olives has been found to reduce blood pressure. In a study conducted on the importance of olive oil, Dr. L. Aldo Ferrara, Associate Professor at the Frederico II University of Naples in Italy discovered that the daily use of 40 grams of olive oil reduced the dosage of blood pressure medication in hypertensive patients by about 50 percent. Polyphenols in extra-virgin olive oil was credited for the significant reduction of blood pressure.
Preliminary studies suggest that fish oil may have a modest effect on high blood pressure. Although fish oil supplements often contain both DHA (docohexaenoic acid) and EPA (eicosapentaenoic acid), there is some evidence that DHA is the ingredient that lowers high blood pressure.