Qualitative Analysis of Secondary Metabolites in Centaurea Senegalensis Plant

Abstract

1. Introduction Medicinal plants have been the mainstay of traditional herbal medicine amongst rural dwellers worldwide since time immemorial. The therapeutic use of plants certainly goes back to the Sumerian and the Akkadian civilizations in about the third millennium BC (Mandal et al. 2005). One of the ancient authors, who described medicinal natural products of plant and animal origins, listed approximately 400 different plant species for medicinal purposes. Medicinal plants have always been considered as a source for healthy life for people. Therapeutic properties of medicinal plants are very useful in healing various diseases and the advantages of these medicinal plants are natural (Kalemba and Kunicka, 2003). Over the years they have assumed a very central stage in modern civilization as natural source of chemotherapy as well as amongst scientist in search for alternative sources of drugs. About 3.4 billion people in the developing world depend on plant-based traditional medicines. This represents about 88 per cent of the world's inhabitants, who rely mainly on traditional medicine for their primary health care. According to the World Health Organization, a medicinal plant is any plant which, in one or more of its organs, contains substances that can be used for therapeutic purposes, or which are precursors for chemo-pharmaceutical semi synthesis. Such a plant will have its parts including leaves, roots, rhizomes, stems, barks, flowers, fruits, grains or seeds, employed in the control or treatment of a disease condition and therefore contains chemical components that are medically active. These non-nutrient's plant chemical compounds or bioactive components are often referred to as phytochemicals (phyto in Greek translation meaning 'plant') or phyto constituents are responsible for protecting the plant against microbial infections or infestations by pests (Doughariet al., 2009). The study of natural products on the other hand is called phytochemistry. Phytochemicals have been isolated and characterized from fruits such as grapes and apples, vegetables such as broccoli and onion, spices such as turmeric, beverages such as green tea and red wine, as well as many other sources (Doughari, 2009). The science of application of these indigenous or local medicinal remedies including plants for treatment of diseases is currently called ethno pharmacology but the practice dates back since antiquity. A plant in which one or more of its organs contains substances that can be used for therapeutic purposes on which are precursors for the synthesis of useful drugs are called medicinal plants. Medicinal plants contain biologically active chemical substances (phytochemicals) such as saponins, tannins, essential oils, flavonoids, alkaloids and other chemical compounds, which have preventive and curative properties. These complex chemical substances of different compositions are found as secondary plant metabolites in one or more of these plants and are useful for humanity (Okigbo, 2000). In view of many diseases defiling drugs, health practices are now changing from curative to preventive medicine. Phytochemicals popular in preventive medicine are flavonoids, polyphenols, saponins, lignoids and vitamins. Also, a knowledge of the chemical constituents of plants is desirable, not only for the discovery of therapeutic agents, but also because such information may be of value in disclosing new sources of such economic materials as tannins, oils, gums, which are precursors for the synthesis of complex chemical substances, etc. In addition, the knowledge of the chemical