INTRODUCTION AND LITERATURE REVIEW
1.1 MEDICINAL PLANTS
The use of plants for healing purposes has always been part of human culture and it is getting increasingly popular in Nigeria. Acalypha wilkesiana is one of several medicinal plants used in Nigeria and it has various ethno botanical uses. Acalypha wilkesiana belongs to the family Euphorbiaceae. It is propagated by stem cuttings at any time of the year. Under ideal conditions, it grows as a spreading evergreen shrub with upright branches that tend to originate near the base and can get up to 3.1 m tall with a similar spread. It has leafs (12.7- 20.3 cm long) that are alternate, elliptic to oval, serrate and multi-coloredans small inconspicuous flowers (10.2-20.3 cm) that hangs in catkin-like racemes beneath the foliage
In some parts of southern Nigeria, the use of diuretics in the treatment of hypertension has been traditionally substituted for aqueous leaf extract of Acalypha wilkesiana. Acute changes in body mass over a short time period can frequently be assumed to be due to body water loss or gain; 1 ml of water has a mass of 1 g and therefore changes in body mass can be used to quantify water gain or loss. Over a short time period, no other body component will be lost at such a rate, making this assumption possible (Shirreffs, 2003), thus weight parameters were evaluated and used as makers of hydration status of the male Wistar rats.
1.1.1 ACALYPHA SPECIE
Subtribe: Acalyphinae Genus Acalypha
Acalypha is a plant genus of the family Euphorbiaceae. It is the sole genus of the subtribe Acalyphinae. With 450 to 500 species of shrubs, trees and annuals, the genus is only behind Euphorbia, Croton and Phyllanthus in terms of Malpighiales diversity. The common name is copperleaf, three-seeded mercury or cat's tail (Pax et al, 1924). These plants are mostly tropical or subtropical, with a few representatives in temperate zones. The Americas contain two thirds of the known species, distributed from southern United States to Uruguay and northern Argentina. Several species, such as Acalypha ecuadorica, Acalypha eggersii and Acalypha raivavensis are nearly extinct, and the St. Helena Mountain Bush or "stringwood" Acalypha rubrinervis already is hispida (chenille plant, red-hot cat's tail), cultivated as a houseplant because of its colourful and texturally exciting flowers, has gained the Royal Horticultural Society's Award of Garden Merit. (Grubben et al, 2004), as has Acalypha hispaniolae (Hispaniola cat's tail). Others are grown for their foliage and a number of cultivars have been developed, such as Acalypha wilkesiana 'Obovata Cristata' and Acalypha wilkesiana Acalypha wilkesiana “Hoffmannii'. Acalypha bipartita is eaten as a vegetable in some parts of Africa.
1.1.2 ACALYPHA WILKESIANA
Species: Acalypha wilkesiana
Binomial name: Acalypha wilkesiana
Acalypha wilkesiana is an evergreen shrub. It grows 3 m high and spreads 2 m across. The stem is erect with many branches. The branches have fine hairs. It has a closely arranged crown. The leaves are coppery green with red splashes of colour. This gives them a mottled appearance. The leaves are large and broad with teeth around the edge. They can be 10–20 cm long and 15 cm wide. The leaves are finely hairy. They can be flat or crinkled. The flowers are reddish in spikes at the end of branches. They have separate male and female flowers on the same plant. The male flowers are in long spikes which hang downwards while the female flowers are in short spikes. They do not show up easily as they are often hidden among the leaves. The flower stalks are 10–20 cm long. A tropical and subtropical plant which grows naturally in Vanuatu. It occurs in the Pacific Islands. It prefers light well drained soil. It suits a protected shady position. It is damaged by both drought and frost. It needs a minimum temperature above 10°C. It suits hardiness zones 9-12. Acalypha wilkesiana ointment is used to treat fungal skin diseases (Oyelami et al, 2003) carried out a non-comparative study to evaluate the safety and efficiency of Acalypha wilkesiana ointment using 32 Nigerians with mycological as well as clinical evidence of mycoses. The ointment successfully controlled the mycoses in 73.3% of the affected patients. It was very effective in treating Pityriasis versicolor, Tinea pedia and Candida intetrigo, with 100% cure (Oyelami et al, 2003) concluded that Acalypha wilkesiana ointment can be used to treat superficial mycoses (Akinyemi et al, 2005) evaluated crude extracts from six important medicinal plants, namely: Phylantus discoideus, Ageratum conyzoides, Terminalia avicennioides, Bridella ferruginea, Acalypha wilkesiana and Ocimum gratissimum, to find activity against methicillin resistant Staphylococcus aureus (MRSA. Water and ethanolic extracts of these plants were obtained locally. MRSA strains isolated from patients were used. Both ethanolic and water extracts showed effects on MRSA. Minimum bactericidal concentration (MBC) and minimum inhibition concentration (MIC) of these plants ranged from 30.4-37.0 mcg/ml and 18.2-24.0 mcg/ml respectively. A high MBS value was found in two plants and the other four contained traceable amounts of anthraquinones. This study provided scientific support for the use of Acalypha wilkesiana, T. avicennioides, O. gratissimum and P. discoidens against MRSA based diseases. A. conyzoides and B. ferruginea were unresponsive against the MRSA strains (Oyelami et al, 2003).
Fig 1: structure of paracetamol
Paracetamol (called acetaminophen in the USA) is one of the most commonly used non-narcotic analgesic and antipyretic agents. It has relatively weak anti-inflammatory activity. Paracetamol is reported to be selective inhibitor of Cox 3 (cyclooxygenase). Although some reported evidence show that paracetamol has significant anti- inflammatory action (Granberg et al, 1999). Paracetamol toxicity is one of the most common causes of poisoning worldwide. In the United States and United Kingdom it is the most common cause of acute liver failure. Paracetamol was the fourth most common cause of death following self-poisoning in the United Kingdom in 1989; (karthikeyan et al., 2005), yet it is still one of the most common analgesic and antipyretic drugs often used around the world to treat pains and mild feverish conditions. As far as this is true, it is also one of the major causes of liver damage such as liver necrosis. Traditionally, a number of herbal medicines have been used in ameliorating this problem of hepatotoxicity such as fresh garlic; (moller et al, 2009), methanolic extract of Acalypha wilkesiana; (khashab et al, 2007).Toxic doses of paracetamol cause a serious potentially fatal hepatotoxicity.
1.2.1 MEDICAL USES OF PARACETAMOL
In medicine paracetamol is used to;
a) Reduce Fever:
Paracetamol is approved for reducing fever in people of all ages. The World Health Organization (WHO) recommends that paracetamol only be used to treat fever in children if their temperature is greater than 38.5 °C (101.3 °F). The efficacy of paracetamol by itself in children with fevers has been questioned and a meta-analysis showed that it is less effective than ibuprofen. Paracetamol has a well-established role in pediatric medicine as an effective analgesic and antipyretic.
b) Reduce Pain:
Paracetamol is used for the relief of pains associated with many parts of the body. It has analgesic properties comparable to those of aspirin, while its anti-inflammatory effects are weaker. It is better tolerated than aspirin in patients in whom excessive gastric acid secretion or prolongation of bleeding time may be a concern. Available without a prescription, it has in recent years increasingly become a common household drug.
1.2.2 PARACETAMOL INDUCED HEPATOXICITY
The toxic effect of paracetamol on the liver occur when the liver enzymes catalyzing the normal conjugation reactions are saturated, causing the drug to be metabolized by the mixed function oxidases. The resulting toxic metabolized, N-acetyl-p- benzoquinoneimine (NAPQI), is inactivated by conjugation with glutathione, but when glutathione is depleted the toxic intermediate accumulates and reacts with nucleophilic constituents in the cell. This causes necrosis in the liver and also in the kidney tubules.
1.2.3 MECHANISM OF ACTION OF PARACETAMOL ON HEPATOXICITY
Metabolic activation of acetaminophen toxicity is metabolically activated by cytochrome P450 to form a reactive metabolite that covalently binds to protein (Mitchell et al,). The reactive metabolite was found to be N-acetyl-p-benzoquinone imine (NAPQI), which is formed by a diret to-electron oxidation (Dahlin et al, 1984). More recently, the cytochromes 2E1, 1A2, 3A4, and 2A6 have been reported to oxidize acetaminophen to the reactive metabolite. Also, Dr. Gillette's laboratory showed that NAPQI is detoxified by glutathione (GSH) to form an acetaminophen-GSH conjugate. After a toxic dose of acetaminophen, total hepatic GSH is depleted by as much as 90%, and as a result, the metabolite covalently binds to cytokine groups on protein, forming acetaminophen-protein adducts (Mitchell et al, 1973). This mechanism is shown in Fig. 2.
Fig 2: showing the schematic representation depicting the role of
Metabolism in acetaminophen toxicity (Mitchell et al, 1973)
Events that produce hepatocellular death following the formation of acetaminophen protein adducts are poorly understood. One possible mechanism of cell death is that covalent binding to critical cellular proteins results in subsequent loss of activity or function and eventual cell death and lysis. Primary cellular targets have been postulated to be mitochondrial proteins, with resulting loss of energy production, as well as proteins involved in cellular ion control (Nelson, 1990).
1.3.1 WEIGHT DETERMINATION
Prior to this research the weight of these wistar rats were determined using
i) A beam balance: this instrument was used to measure the body weight of the rats
ii) An electronic weigh balance: this instrument was used to measure the organ weight of the rats
1.3.2 WEIGHT ASSOCIATED DISEASES
Excess body weight is a very serious problem, especially in North America and Europe. It has been referred to as a "pandemic" since it has progressively increased over the past several decades. Moreover, excess body weight significantly increases the risk of numerous diseases and clinical disorders, including all-cause mortality, coronary and cerebrovascular diseases, various cancers, type 2 diabetes mellitus, hypertension, liver disease and asthma, as well as psychopathology, among others. Unfortunately, overweight and obesity are now common in both young children and adolescents. Although the causes of excess body weight are multi-factorial, the most important factors are excess caloric intake coupled with limited energy expenditure. Therefore, lifestyle modification can significantly reduce the risk of morbidity and mortality and thereby increase longevity and improve the quality of life.
1.4 ORGAN WEIGHT OF RATS
1.4.1 THE LIVER
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion. The liver is necessary for survival; there is currently no way to compensate for the absence of liver function in the long term, although new liver dialysis techniques can be used in the short term.
This organ plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification. It lies below the diaphragm in the abdominal-pelvic region of the abdomen. It produces bile, an alkaline compound which aids in digestion via the emulsification of lipids. The liver's highly specialized tissues regulate a wide variety of high-volume biochemical reactions, including the synthesis and breakdown of small and complex molecules, many of which are necessary for normal vital functions.
The liver is a reddish brown organ with four lobes of unequal size and shape. A human liver normally weighs 1.44–1.66 kg (3.2–3.7 lb), and is a soft, pinkish-brown, triangular organ. It is both the largest internal organ (the skin being the largest organ overall) and the largest gland in the human body. It is located in the right upper quadrant of the abdominal cavity, resting just below the diaphragm. The liver lies to the right of the stomach and overlies the gallbladder. It is connected to two large blood vessels, one called the hepatic artery and one called the portal vein. The hepatic artery carries blood from the aorta, whereas the portal vein carries blood containing digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas. These blood vessels subdivide into capillaries, which then lead to a lobule. Each lobule is made up of millions of hepatic cells which are the basic metabolic cells. Lobules are the functional units of the liver.
Two major types of cells populate the liver lobes: karat parenchymal and non-parenchymal cells. 80% of the liver volume is occupied by parenchymal cells commonly referred to as hepatocytes. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. Sinusoidal endothelial cells, Kupffer cells and hepatic stellate cells are some of the non-parenchymal cells that line the hepatic sinusoid. The liver is also prone to many diseases. The most common include infections such as hepatitis A, B, C, D, E, alcohol damage, fatty liver, cirrhosis, cancer, drug damage (particularly by acetaminophen (paracetamol) and cancer drugs). Many diseases of the liver are accompanied by jaundice caused by increased levels of bilirubin in the system. The bilirubin results from the breakup of the hemoglobin of dead red blood cells; normally, the liver removes bilirubin from the blood and excretes it through bile. There are also many pediatric liver diseases including biliary atresia, alpha-1 antitrypsin deficiency, alagille syndrome, progressive familial intrahepatic cholestasis, and Langerhans cell histiocytosis, to name but a few. Diseases that interfere with liver function will lead to derangement of these processes. However, the liver has a great capacity to regenerate and has a large reserve capacity. In most cases, the liver only produces symptoms after extensive damage.
Liver diseases may be diagnosed by liver function tests, for example, by production of acute phase proteins.
1.4.2 THE KIDNEY
The kidneys are organs that serve several essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and regulation of blood pressure (via maintaining salt and water balance). They serve the body as a natural filter of the blood, and remove wastes which are diverted to the urinary bladder. In producing urine, the kidneys excrete wastes such as urea and ammonium, and they are also responsible for the reabsorption of water, glucose, and amino acids. The kidneys also produce hormones including calcitriol, erythropoietin, and the enzyme renin.
1.4.3 THE HEART
The heart is a hollow muscle that pumps blood throughout the blood vessels by repeated, rhythmic contractions. It is found in all animals with a circulatory system (including all vertebrates). The vertebrate heart is principally composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue found only in this organ and responsible for the ability of the heart to pump blood. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males.
1.4.4 THE BRAIN
The brain is the centre of the nervous system in all vertebrate and most invertebrate animals—only a few invertebrates such as sponges, jellyfish, adult sea squirts and starfish do not have one, even if diffuse neural tissue is present. It is located in the head, usually close to the primary sensory organs for such senses as vision, hearing, balance, taste, and smell. The brain of a vertebrate is the most complex organ of its body. In a typical human the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons, each connected by synapses to several thousand other neurons. These neurons communicate with one another by means of long protoplasmic fibres called axons, which carry trains of signal pulses called action potentials to distant parts of the brain or body targeting specific recipient cells.
1.4.5 THE TESTES
The testicle (from Latin testiculus, diminutive of testis, meaning "witness" of virility,plural testes) is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system. The primary functions of the testes are to produce sperm (spermatogenesis) and to produce androgens, primarily testosterone. Both functions of the testicle are influenced by gonadotropic hormones produced by the anterior pituitary.
1.4.6 THE LUNGS
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart. Their principal function is to transport oxygen from the atmosphere into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere. This exchange of gases is accomplished in the mosaic of specialized cells that form millions of tiny, exceptionally thin-walled air sacs called alveoli.
1.5 OBJECTIVE OF STUDY
The objective of this study is to determine the effect of methanolic leaf extract of Acalypha wilkesiana in paracetamol induced hepatoxicity on the weight parameters of Wistar rats
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