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Buchu Leaf

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Pharmacogn Rev. 2011 Jan-Jun; 5(9): 30–40. 

doi: 10.4103/0973-7847.79097

PMCID: PMC3210006

PMID: 22096316

Role of natural herbs in the treatment of hypertension

Nahida Tabassum and  Feroz Ahmad

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This article has been cited by other articles in PMC.

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Abstract

Hypertension (HTN) is the medical term for high blood pressure. It is dangerous because it makes the heart work too hard and contributes to atherosclerosis (hardening of arteries), besides increasing the risk of heart disease and stroke. HTN can also lead to other conditions such as congestive heart failure, kidney disease, and blindness. Conventional antihypertensives are usually associated with many side effects. About 75 to 80% of the world population use herbal medicines, mainly in developing countries, for primary health care because of their better acceptability with human body and lesser side effects. In the last three decades, a lot of concerted efforts have been channeled into researching the local plants with hypotensive and antihypertensive therapeutic values. The hypotensive and antihypertensive effects of some of these medicinal plants have been validated and others disproved. However, ayurvedic knowledge needs to be coupled with modern medicine and more scientific research needs to be done to verify the effectiveness, and elucidate the safety profile of such herbal remedies for their antihypertensive potential.

Keywords: Antihypertensive, herbs, hypotensive, hypertension, medicinal plants

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INTRODUCTION

Hypertension (HTN) or high blood pressure (BP) is a chronic medical condition in which the BP in the arteries is elevated. It is classified as either primary (essential) or secondary. About 90 to 95% of cases are termed primary HTN, which refers to high BP for which no medical cause can be found.[1] The remaining 5 to 10% of cases, called secondary HTN, are caused by other conditions that affect the kidneys, arteries, heart, or endocrine system.[2]

Persistent HTN is one of the risk factors for strokes, heart attacks, heart failure, and arterial aneurysm, and is a leading cause of chronic kidney failure.[3] Moderate elevation of arterial BP leads to shortened life expectancy. Both dietary and lifestyle changes as well as medicines can improve BP control and decrease the risk of associated health complications.

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CLASSIFICATION

HTN is usually classified based on the systolic and diastolic BPs. Systolic BP is the BP in vessels during a heartbeat. Diastolic BP is the pressure between heartbeats. A systolic or the diastolic BP measurement higher than the accepted normal values for the age of the individual is classified as pre-HTN or HTN.

HTN has several subclassifications including, HTN stage I, HTN stage II, and isolated systolic HTN. Isolated systolic HTN refers to elevated systolic pressure with normal diastolic pressure and is common in the elderly. These classifications are made after averaging a patient's resting BP readings taken on two or more office visits. Individuals older than 50 years are classified as having HTN if their BP is consistently at least 140 mmHg systolic or 90 mmHg diastolic. Patients with BP s higher than 130/80 mmHg with concomitant presence of diabetes or kidney disease require further treatment. HTN is also classified as resistant if medications do not reduce BP to normal levels.[4] Exercise HTN is an excessively high elevation in BP during exercise.[5] The range considered normal for systolic values during exercise is between 200 and 230 mmHg.[6] Exercise HTN may indicate that an individual is at risk for developing HTN at rest.[7]

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CAUSES

Essential Hypertension

Essential HTN is the most prevalent type of HTN, affecting 90 to 95% of hypertensive patients.[1] Although no direct cause has identified itself, there are many factors such as sedentary lifestyle, stress, visceral obesity, potassium deficiency (hypokalemia),[8] obesity,[9] (more than 85% of cases occur in those with a body mass index greater than 25),[10] salt (sodium) sensitivity,[11] alcohol intake,[12] and vitamin D deficiency that increase the risk of developing HTN.[13] Risk also increases with aging,[14] some inherited genetic mutations,[15] and having a family history of HTN.[16] An elevation of renin, an enzyme secreted by the kidney, is another risk factor,[17] as is sympathetic nervous system over activity.[18] Insulin resistance, which is a component of syndrome X, or the metabolic syndrome, is also thought to contribute to HTN. Consuming foods that contain high fructose corn syrup may increase one's risk of developing HTN.[19]

Secondary hypertension

Secondary HTN by definition results from an identifiable cause. This type is important to recognize since it is treated differently than essential HTN, by treating the underlying cause of the elevated BP. HTN results compromise or imbalance of the pathophysiological mechanisms, such as the hormone-regulating endocrine system, that regulate blood plasma volume and heart function. Many conditions cause HTN. Some are common and well-recognized secondary causes such as Cushing's syndrome, which is a condition where the adrenal glands overproduce the hormone cortisol.[20] In addition, HTN is caused by other conditions that cause hormone changes such as hyperthyroidism, hypothyroidism, and adrenal gland cancer. Other common causes of secondary HTN include kidney disease, obesity/metabolic disorder, pre-eclampsia during pregnancy, the congenital defect known as coarctation of the aorta, and certain prescription and illegal drugs.

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PATHOPHYSIOLOGY

Most of the mechanisms associated with secondary HTN are generally fully understood. However, those associated with essential (primary) HTN are far less understood. What is known is that cardiac output is raised early in the disease course, with normal total peripheral resistance (TPR). Over time, cardiac output drops to normal levels, but TPR is increased. The following three theories have been proposed to explain this:

 

  • Inability of the kidneys to excrete sodium, resulting in natriuretic factors such as atrial natriuretic factor being secreted to promote salt excretion with the side effect of raising TPR.

  • An overactive renin-angiotensin system leads to vasoconstriction and retention of sodium and water. The increase in blood volume leads to HTN.[21]

  • An overactive sympathetic nervous system, leading to increased stress responses.[22]

  • It is also known that HTN is highly heritable and polygenic (caused by more than one gene) and a few candidate genes have been postulated in the etiology of this condition.[23]

 

Recently, work related to the association between essential HTN and sustained endothelial damage has gained popularity among HTN scientists. It remains unclear however whether endothelial changes precede the development of HTN or whether such changes are mainly due to long-standing elevated BPs.

HTN is a major independent risk factor for coronary artery disease, stroke, and kidney failure. Each increase of 20 mmHg in systolic BP and 10 mmHg in diastolic BP, over the range of 115/75 to 185/115 mmHg, doubles the risk of a fatal coronary event.

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