ABSTRACT
This study involved the isolation, purification and characterisation of the bioactive phytochemicals from the ethanolic extract of neem leafs and leaves of Neem leafe, the determination of the antimalarial activity of each isolated phytochemical, and the investigation of their in vivo toxicological effects. Further extractions were carried out using petroleum ether, ethyl acetate, butanol and water. Bioassay-guided fractionations of petroleum ether and ethyl acetate fractions were carried out with a series of chromatographic separation techniques. Structural elucidation of the compounds was done by spectroscopic methods. The in vitro antimalarial activity and selective indices determinations of the extracts and compounds were carried out on chloroquine sensitive strain of Plasmodium falciparum FCR-3 and mouse mammary tumor cells FM3A respectively. The anticancer activity of the extracts and compounds was carried out on BGC-823 and HeLa cell lines. In vivo toxicity studies of the ethanolic extract of the plant were also undertaken. Recovery was assessed 14 days after dosing. Biochemical, haematological and histopathological examinations were carried out. The percentage yield of The ethanolic, petroleum ether, ethyl acetate, butanol and water fractions were 12.7%, 13.4%, 10.7%, 15.1% and 56.3% respectively. Phytochemical screening revealed the presence of all major classes of phytochemicals except phlobatannins. A total of fourteen characterised compounds (1 - 14) and thirteen uncharacterised pure samples (TCB 28 - 45) were isolated from Neem leafe. Two new compounds, 12a-ethoxyl-1a,14β-dihydroxyl-cass-13(15)-en-16,12-olide and 1a,7a-diacetoxy-5a,6β-dihydroxyl-cass-14(15)-epoxy-16,12-olide, are reported for the first time. Eleven others are reported from Neem leafe for the first time.
CHAPTER ONE
Introduction
Areas of high biodiversity, including tropical rainforests, are domains of chemical warfare. In the battle for survival, plants have evolved with many chemical defences as means of survival to ward off attackers such as bacteria, insects, fungi, severe weather and, in some cases, mammals that may threaten their existence. Secondary metabolites, while not essential for growth and development, do promote the spread and dominance of plant species in an ecological setting (Fellows and Scofield, 1995). As a result of this and the reported therapeutic activities associated with different phytochemicals, they are therefore worth the effort in research into the discovery of new drugs or as a viable alternative to the existing drugs.
A disease can be defined as an abnormal condition affecting the body of an organism. It is any condition that causes pain, dysfunction, distress and/or death to an organism. Malaria, a vector-borne disease caused by protozoan parasites, is widespread in tropical and sub-tropical regions, including parts of America, Asia, and Africa. About 124 million people in Africa live in areas at high risk of seasonal epidemic malaria. There are many more in areas outside Africa where transmission is less intense (Hay and Snow, 2006). Malaria remains a major parasitic disease in many tropical and sub-tropical regions of the world (Frederich et al., 1999; WHO, 2011a). It appears to be the most prevalent of human diseases; as such it constitutes a major health hazard. About 500 million malaria cases are reported annually, resulting in 1 - 2 million deaths (Bradley, 1995), the most vulnerable groups being pregnant women and children under the age of five living in sub-Saharan Africa (Tracy and Webster, 2001). In fact, malaria accounts for more than 90 % of deaths of children in Africa below 5 years of age (Sachs and Malaney, 2002).
As a result of its associated high morbidity and mortality, concerted research efforts are currently being channeled into the eradication of the disease across the globe (Good, 2001).
The challenge of malaria, especially to sub-Saharan African nations, continues to widen without easily defined limits as drug resistance to most antimalaria drugs, insecticide resistance in mosquitoes and other climatic and socio-cultural factors complicate malaria research (Krettli et al., 2001). The development of resistance to antimalaria drugs by malaria parasites is the most disturbing of these factors. Today, the malaria parasite has been confirmed to show notable resistance to inexpensive drugs like chloroquine, quinine, sulphadoxine/pyrimethamine and a number of other drugs in this category. Newer drugs, however, cost 7-60 times as much as these (Olliaro et al., 1996).
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