CHAPTER ONE

1.0 INTRODUCTION

Polyphenols arenaturalorganic chemicals characterized by the presence of large number

of phenol structural units (Quideauet al., 2011). The most research-informed and

chemistry-aware definition of polyphenol is termed the White–Bate-Smith–Swain–

Haslam (WBSSH) definition (Haslam and Cai, 1994) which describes the polyphenol as

moderately water-soluble compounds, with molecular weight of 500–4000 Dalton,having

more than 12 phenolic hydroxyl groups and with 5–7 aromatic rings per 1000 Da.The

number and characteristics of the phenol structures underlie the unique physical,

chemical, and biological properties of a particular member of the polyphenol

class(Quideau et al., 2011).

Over the past 10 years, researchers and food manufacturers have become increasingly

interested in polyphenols. The main reason for this interest is the recognition of the

antioxidant properties of polyphenols, their great abundance in our diet, and their

probable role in the prevention of various diseases associated with oxidative stress, such

as cardiovascular, cancer and neurodegenerative diseases. As the major active substance

found in many medicinal plants, itmodulates the activity of a wide range of enzymes and

cell receptors.Polyphenols as antioxidants, helps in addressing and reversing the

problems caused by oxidative stress to the walls of arteries, create a heart-healthy

environment by curbing the oxidation of low density lipoprotein cholesterol which stops

the potential for atherosclerosis, and they help relieve chronic pain, as seen in conditions

like rheumatoid arthritis , due to their anti-inflammatory properties.

In addition to having

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antioxidant properties, polyphenols have several other specific biological actions that are

yet to be understood(Quideau et al., 2011).

Plants has been a source of medicinal agents for thousands of years, and an impressive

number of modern drugs have been isolated from natural sources, many based on their

use in traditional medicine (Hostettmann et al., 2000). These plants continue to play an

essential role in health care, with about 90% of the world‟s inhabitants depending mainly

on traditional medicines for their primary health care (Hostettmann et al., 2000).

Recently, there has been an upsurge of interest in the therapeutic potentials of medicinal

plants antioxidants reducing free radical related diseases. It has been mentioned that the

antioxidant activity of plants might be due to their phenolic compounds (Cook and

Samman, 1996).

Vitex doniana is a deciduous tree, usually 4-8m high, with a dense rounded crown. Its

bark is light grey with numerous vertical fissures. The leaves are long stalked with 5-7

leaflets. The leaflets are usually widest towards the tip, more or less hairless. The fruits

are ellipsoid to oblong, green turning black on ripening. It is a savanna species in wooded

grassland and can also be found along forest edges. It is extremely widespread in tropical

Africa. It is commonly known as Black Plum or African olive (Glew et al., 1997), Dinya

(Hausa),Galbihi (Fulani),Oori-nla (Yoruba), Ucha coro (Igbo), and is wide spread in the

southwestern Nigeria as a perennial tree. Earlier reports have shown that aqueous root

bark extract of the plant can be used for the treatment of anaemia (Abdulrahman et al.,

2010), methanolic stem bark extract can be used for the treatment of gastroenteritis,

diarrhoea, dysentery (Kilani, 2006) and aqueous leaves and stem bark extracts for the

treatment of liver disorder (James et al., 2010). The ability of an aqueous extract of Vitex

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doniana stem bark to protect the liver of albino rats from carbon tetrachloride-induced

liver damage was reported by Ladeji and Okoye (1996).

Hyperlipidemia is an elevation of one or more of the plasma lipids, including cholesterol,

cholesterol esters, triglycerides and phospholipids (Raasch, 1988). It is the most common

form of dyslipidemia. It is well established that elevated blood lipid levels

(hyperlipidemia)constitute the primary risk factor for atherosclerosis (Saunders, 2007).

There is now overwhelming evidence that, dietary factors, nutritional habits and genetic

origin influence the risk of coronary artery diseases (Van Horn, 1997). Increased levels of

high-density lipoprotein cholesterol (HDL-c) are associated with a decreased

cardiovascular risk (Wanner and Quaschning 2001; Kourounakisetal., 2002,).

Predominant cardiovascular diseases associated with hyperlipidemia arehypertension,

ischemic heart diseases, stroke, coronary heart diseases and atherosclerosis.They account

for at least 80% of the burden of cardiovascular disease in both developing and developed

countries, which shares many of the same common risk factors (Balakumar et al., 2007).

Hyperlipidemia is divided into primary and secondary subtypes. Primary hyperlipidemia

is usually due to genetic causes such as a mutation in a receptor protein, while secondary

hyperlipidemia arises due to other underlying causes such as diabetes. (Chait and

Brunzell, 1990). Traditionally, factors such as hypercholesterolemia, cigarette smoking,

diabetes mellitus and sedentary life style have been implicated in the development of

hyperlipidemia and atherosclerotic cardiovascular disease (Frohlich and Lear, 2002).

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1.1 Statement of Research Problem

Hyperlipidemia is one of the greatest risk factors contributing to the prevalence and

severity of cardiovascular disease (Grundy, 1986). It accounts for about 56% of stroke,

18% of ischemic heart disease and more than 4 million deaths per year globally (WHO

2002).In Nigeria, it accounts for about (45–73) % death per year (Ebesunum et. al.,

2008). Cardiovascular diseases are one of the major causes of death worldwide (Murray

and Lopez, 1996).Although several factors, such as diet high in saturated fats and

cholesterol, age, family history, hypertension and life style play a significant role in

causing heart failure.High levels of cholesterol particularly total cholesterol, triglycerides

and low density lipoprotein cholesterol is mainly responsible for the onset of CHDs

(Choudhary et al., 2005). About 20% reduction of blood cholesterol level can decrease

about 31% of CHD incidence and 33% of its mortality rate (Marzyieh et al., 2007).

Cardiovascular disease covers a wide array of disorders, including disease of the cardiac

muscle and of the vascular system supplying the heart, brain, and other vital organs

(Bently et al., 2002). Predominant cardiovascular diseases associated with hyperlipidemia

are hypertension, ischemic heart disease, stroke, coronary heart disease and

atherosclerosis (Balakumar et al., 2007). Hyperlipidemia is asymptomatic, characterized

by elevated serum total cholesterol, low density lipoprotein, very low density lipoprotein

and decreased high density lipoprotein levels.Hyperlipidemia associated with lipid

disorders are considered to cause atherosclerotic cardiovascular diseases (Saravanan et.

al., 2003). Among these are hypercholesterolemia, hypertriglyceridemia and ischemic

heart disease (Kaesancini and Krauss, 1994).

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1.2 Justification

Polyphenols are natural products found in fruits and vegetables, as well as in beverages

such as tea and red wine. Recent datasuggests that diet rich in these compounds is

associated with a decreased risk of cardiovascular diseases such as atherosclerosis,

ischemic heart disease, stroke, coronary heart disease and hypertension. Their effects are

also believed to underlie part of the improved cardiovascular health ascribed to the

„French paradox‟. Polyphenols are hypothesized to provide cardio-protective effects

through their ability to scavenge free radicals and inhibit lipid peroxidation. As

antioxidants, they help in addressing and reversing the problems caused by oxidative

stress to the walls of arteries, create a heart-healthy environment by curbing the oxidation

of LDL cholesterol, and they help relieve chronic pain, as seen in conditions

like rheumatoid arthritis , due to their anti-inflammatory properties.

Recent works are available on the scavenging potential of the aqueous extract of Vitex

doniana in the treatment of carbon tetrachloride induced liver damage, but there is no

documentated work on the effect of itsethanol extractson hyperlipidemic rats.Hence there

is a need to investigate the effect of these extracts on hyperlipidemic rats.

1.3 Aim and Objectives

The general aim of this study is to investigate theantihyperlipidemic effect of ethanol

extracts from different parts (leaves, stem and root bark) ofVitex doniana in therats, with

a view of providing a pharmacological justification and for the use of the plant in the

management, control and/or treatment of hyperlipidemic relateddiseases.

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1.3.1 Specific objectives

1. To carry out the plant phytochemicalscreening, extracts total polyphenol and in vitro

antioxidant activity.

2.To carry out in vivoantihyperlipidemic activity of the extractsand quantitative

phytochemical of most potent extract.

3. To determine the effect of the extract onlipid profile andsomebiochemicalparameters

of the hyperlipidemic and normal rats.

4.To determine the effect of the extract on lipid peroxidationand endogenous antioxidant

enzymesin hyperlipidemic and normal rats.

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