EFFECT OF METHANOLIC LEAF EXTRACT OF ACALYPHA WILKESIANA ON WEIGHT PARAMETERS IN PARACETAMOL INDUCED HEPATOXICITY IN MALE WISTAR RAT

ABSTRACT

The potential effect of methanolic extract of the leaves of Acalypha wilkesiana on the weight of wistar rats was investigated. Calculated amount of methanolic leaf extract of Acalypha Wilkesiana were constituted in distilled water from the stock solution to give doses of 500,500 and 1000 mg/kg body weight of paracetamol, vitamin C and leaf extract respectively and administered to the various groups (A, B, C and D). Prior to the administration of methanolic leaf extract of Acalypha Wilkesiana at every interval of seven days, the body weights of the animals were recorded. The acute administration of the aqueous leaf extract of  Acalypha wilkesiana  did not result in obvious signs of morphological changes or death of male rats throughout the experimental period. A significant difference (P>0.05) was obtained in the average body weight of animals administered with the extract as compared with the paracetamol treated group. The organ weight  also elucidated no significant differences (P<0.05) in the kidney, brain, heart, lung and pancreas except for the liver where there was an increase in the weight of the liver treated with extract as compared to that of the rats treated with paracetamol. From the results obtained it is shown that the extract altered the weight of the liver and is therefore not hepatoprotective, this extract should undergo further investigation before oral administration is recommended.

CHAPTER ONE

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

(Al-attar, 2010).

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.

• ACALYPHA SPECIE                                     

Kingdom:                    Plantae

Order:                        Malpighiales

Family:                       Euphorbiaceae

Subfamily:                Acalyphoideae

Tribe:                      Acalypheae

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 wilkesianaAcalypha wilkesiana “Hoffmannii‘. Acalypha bipartita is eaten as a vegetable in some parts of Africa.

1.1.2 ACALYPHA WILKESIANA

Kingdom:                        Plantae

Order:                             Malpighiales

Family:                            Euphorbiaceae

Genus:                             Acalypha

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).

• PARACETAMOL

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.

• MEDICAL USES OF PARACETAMOL

In medicine paracetamol is used to;

1. 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.

1. 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.

• 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    WEIGHT

1.3.1 WEIGHT DETERMINATION

Prior to this research the weight of these wistar rats were determined using

1. A beam balance: this instrument was used to measure the body weight of the rats
2. 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.