Abstract
The study was carried out to determine pharmacognostic standards, phytochemical constituents, evaluate the antioxidant and hepatoprotective activities of the extract and fractions of Annona senegalensis Pers. (Annonaceae) by employing both the in vitro and in vivo experimental models. The acute toxicity tests result showed the drug is safe at 5000mg/kg doses.
The effect of DPPH free radical scavenging, ABTS radical scavenging, Hydroxyl radical scavenging, Hydrogen peroxide scavenging, lipid peroxidation assay, assay of catalase, superoxide Dismutase assay, total protein, β-carotene bleaching, FRAP scavenging, liver and superoxide anion radical scavenging activities were evaluated. Hepatoprotective effects of the extract was evaluated against CCl4 induce liver damage. Carbon tetrachloride (CCl4) induce hepatotoxicity was evaluated by significant increase ( p < 0.05 ) in serum AST, ALT, ALP activity and bilirubin level accompanied by significant decrease ( p > 0.05 ) lipid peroxidation, and catalase activity in liver tissue. All these parameters were also evaluated using the n–hexane, ethyl acetate, methanol fractions.
The results showed that the extract/fractions of stem bark of A. senegalensis had better antioxidant activities at high concentrations when compared to the standard. Co-administration of the extract/fractions (400mg/Kg) protects the CCl4 – induced lipid peroxidation, restored altered serum elevated enzymes. It showed that it is dose dependent.
The results obtained in the present study indicate that the stem bark is a potential source of natural antioxidants.
CHAPTER ONE
1.0 INTRODUCTION
There is amazing abundance of plant life in rain forest and nature has blessed the mankind with a treasure of herbal remedy secrets that offer new approaches to health and healing. It is quite interesting to discover that different herbs can be indicated for a vast number of health problems. Therefore, a lot of scientific screening and research have been going on into investigating the various constituents of plants that are responsible for a particular activity or more, despite all odds. Many drugs have been discovered by the exploitation of traditional medicine since the early dates of human existence (Nwaogu, 1997). Plants have invariably been a rich source for new drugs and some antioxidant drugs in use today were either obtained from plants or developed using their chemical structures as templates(Nwaogu, 1997).
Currently, there is an increasing awareness of the value of traditional medicine and the necessity for improving its standard. Indeed, the Organization of African Unity (O.AU) has in the last few years, held lots of international symposia and these were on a particular aspect of a subject, notably medicinal plants. It has been observed that many plants contain a variety of phytochemical substances, which have appreciable physiological and pharmacological actions on man and animals. Researches on natural products over the years have revealed enormous potentials of plants as source of medicinal agents. Plants are no longer being cultivated for food alone, but also as sources of drugs.
Herbal medicine, which is the oldest form of healthcare known to mankind, involves the use of herbs (medicinal plants) for therapeutic or medicinal purposes. Herbal medicine can be broadly classified into various systems: traditional Chinese herbalism, which is part of the traditional oriental medicine; Ayurveda herbalism, which is derived from Ayurveda; and Western herbalism, which originally came from Greece and Rome to Europe and then spread to North and South America.
The medicinal plants which may be leaves, stems, roots, flowers, seeds, fruits or whole plant or any combination of these parts are prepared in various forms for therapeutic purposes. From a scientific approach, most of the preparations are considered unscientific since they are not pharmacologically authenticated or standardized and are seen as unrefined.
Many plants have varied pharmacological effects which have been confirmed. Extracts of Digitalis spp, Colchicumautomnale, Catharanthusroseus and Peyotecactus had cardio – active, anti – inflammatory, anti – neoplastic and central nervous system actions respectively. It is already estimated that 122 drugs from 94 plants species have been discovered throughethno botanical leads. Plants commonly used in traditional medicines assumed to be safe due to their long usage in the treatment of disease according to knowledge accumulated over centuries. However, recent scientific findings had shown that many plants used as food or in traditional medicine are potentially toxic, mutagenic and carcinogenic (Schimmer et al., 1994).
Cancer chemoprevention by using antioxidant approaches has been suggested to offer a good potential in providing important fundamental benefits to public health, and is now considered by many clinicians and researchers as a key strategy for inhibiting, delaying, or even reversal of the process of carcinogenesis. The cancer chemopreventive activities of naturally occurring phytocompounds are of great interest.
Liver diseases such as jaundice, cirrhosis and fatty liver diseases are very common and large public health problem in the world. Jaundice and hepatitis are two major hepatic disorders that account for a high death rate. There is no rational therapy available for treating liver disorders and management of liver diseases is still a challenge to the modern medicine. The modern medicines have little to offer for alleviation of hepatic ailments whereas most important representatives are of phytoconstituents .The traditional system of medicine like Ayurveda and Siddha system of medicine, Unani system, Chinese system of medicine, Kampoo (Japanese) system of medicine have a major role in the treatment of liver ailments.
Some medicinal plants are used in treatment of hepatobiliary pathologies. Many Nigerian ethno botanic traditions propose a rich repertory of medicinal plants used by the population for treatment of liver diseases. However, there were not enough scientific investigations on the hepatoprotective activities conferred to these plants. One of such plant from Nigerian flora is Annona senegalensisPers.It is believed in folkore that the fruit obtained from this multipurpose plant is widely used locally in the treatment of two commonly energy deficiency syndrome known as kwashiorkor and marasmus. Dalziel, (1995) made report about the plant to be of great medicinal value and its used in native medicine to treat headache and body ache, eyelid swelling. The stem bark of A. senegalensis is used by local populations all over Africa in treating guinea worms, diarrhea and especially in northern Nigeria, gastroenteritis, snake bites, toothache, respiratory infections and malaria. Awa and colleagues (2012) reported the use of leaves in the treatment of pneumonia, and as a stimulant to improve health. A decoction from the roots is used to stop chest colds, venereal diseases, stomach ache and dizziness (Jiofack. et al., 2010).
Many indigenous herbal plants of regional interest have been used popularly as folk medicines in Nigeria or other African countries; however, their bioactivities or pharmacological effects are to be investigated.
