CHAPTER ONE
INTRODUCTION
1.0 Background of the study
Medicinal plants are commonly used in treating andpreventing specific ailments and diseases and theyare generally considered to be harmful to humans (Awomukwu et al., 2014). Plant materials are sources of food, shelter and medicinal compounds which have been known to play a dominant role in the maintenance of human health in most rural communities in the developing countries (Moghadamtousiet al., 2015). Natural products, especially those derived from plants, have been used to help mankind sustain its health since the dawn of medicine. Both plants and vegetables vary considerably in their nutrient contents and are good sources of vitamins, proteins, essential amino acids as well as minerals and antioxidants. Although there are various drugs for the treatment of inflammation, they are not affordable to many people especially those in the developing countries such as Nigeria. In addition, the rural population in various parts of the world do not have adequate access to high quality drugs for treatment of inflammation, so they depend heavily on plants and herbal products for treatments of diseases.Medicinal plants plays vital role in drug discovery, as plants have the ability to synthesize a wide variety of phytochemical compounds as secondary metabolites, many of which are being used to treat the various diseases of mankind (Jachak and Salani, 2007). Herbal medicine is fast emerging as an alternative to available synthetic drugs for the treatment of diseases possibly due to lower cost, more availability, fewer adverse effects and perceived effectiveness (Vermaet al., 2012). The traditional system of medicine has been such that a large percentage of the population in Africa depends on indigenous system for relief of symptoms. With such huge section of an ever-increasing population relying on herbal remedies, it is imperative that plant products, which have been in use from ages, have scientific support for their efficacy (Chandraet al., 2009). The World Health Organisation (WHO) has shown great interest in plant derived medicines which have been described in the folklore medicines of many countries (Mukherjee, 2008). However, the historic role of medicinal plants in the treatment and prevention of diseases (Padma, 2001), and their role as catalyst in the development of pharmacology do not however, assure their safety for uncontrolled use by an uniformed public (Matthews et al., 2000). More than 50 per cent of all modern drugs are natural plant products in origin and are essential in drug development programme of the pharmaceutical industry (Burton et al., 1985). Over the past century, phytochemicals in plants have been a pivotal pipeline for pharmaceutical discovery. The importance of the active ingredients of plants in agriculture and medicine has stimulated significant scientific interest in the biological activities of these substances (Moghadamtousi et al., 2013). On a pharmaceutical landscape, plants with a long history of use in ethnomedicine are a rich source of active phytoconstituents that provide medicinal or health benefits against various ailments and diseases. One such plant with extensive traditional use is Annona muricata.
1.1Ecological and some Botanical Description of Annona muricata Plant
Annona muricata is a member of the Annonaceae family(De Feo, 1992). The Natural Resources Conservation Service has shown that, Annonaceae is the custard apple family and is a family of flowering plants consisting of trees, shrubs, or rarely lianas. With about 2300 to 2500 species and more than 130 genera, it belongs to the genus Annona and the family areconcentrated in the tropics, with few species found in temperate regions (Popenoe and Wilson, 1920). A. muricata, also known as Ebo in Yoruba, sawansop in Igbo, Tuwon biri in Hausa and soursop in English-speaking countries is referred to by numerous commonnames including, graviola and guanabana (Thompson, 2003). It is an evergreen plant that is mostly distributed in tropical and subtropical regions of the world (Popenoe and Wilson, 1920). About 900 species are Neotropical, 450 are Afrotropical, and the other species Indomalayan. Guyabano is adaptable to tropical climate and is currently cultivated for its fruit in most Southeast Asian countries such as Malaysia, Indonesia and Philippines (Morton, 1987). The soursop is an upright, low-branching tree reaching 8 to 10 meters (Samson, 1980). The tree hasgreen, glossy evergreen leaves. The flowers appear anywhere on the trunk or any branch (Salazar, 1965). It is usually grown from seedswhich can be stored for several months before planting. Germination of seeds usually takes 3 weeks, but under sub-optimal conditions can be delayed for up to 2–3 months. Alternatively, propagation of the Annona species is achieved by cuttings for rapid multiplication of new genotypes and for the elimination of viral and disease infection (Mowry and Wolfe, 2003). With the exception of a few cultivars, clonal propagation of the Annona species by cutting or air layering has not been very successful. Vegetative propagation of rootstocks or cultivars of known agronomic potential could eliminatetree to tree variability in growth and productivity (George and Nissen, 2009). However, the seedling rootstocks arehighly variable in vigour and disease resistance and consequently scion growth and productivity are also variable. They are considered as minor tropical fruits due to strict environmental requirements for tree planting and the shortpost-harvest life of their fruits (Encina, 2005). The soursop is a large fruit of a small, fast-growing tree. The fruit has the most delicious flavour and is picked from the tree before it has fully ripened as it is badly bruised if allowed to ripen and fall. The fruit is mature and is ready for eating when it feels slightly soft and is light green externally (Worrell et al., 2007). The skin is thin and is covered with conical nibs. The white, pulpy flesh, which contains juice, is peppered with small shiny, black inedible seeds, and has a pleasant, sweet-acidic taste. As it is rather fibrous, its squeezed juice makes a better choice, and has, infact become more popular than the fresh fruit as such. Soursop has few seedless varieties, but they are rare, and tend to have fibrous flesh(Paull et al., 2010).
