PHYTOCHEMICAL CONTENT IN WHITE YAM AND WATER YAM
CHAPTER ONE
1.0    INTRODUCTION
    The investigation of phytochemicals content in white yam and water yam are natural bioactive compounds presented in plants diatary fibre to protect against disease according to Okwu (2004).  Research works have shown the phytochemicals working in conjunction with the nutrients found in food plants may help to slow down the aging process and reduces the risk of many disease including heart diseases, stroke, urinary tracts injections cataracts and osteoporosis in humans.  They can have a complete and over lapping mechanism of actions including antioxidant effects, antibacterial effect, antiviral effects, antifungal effects and modulation of hormone metabolism (Okwu 2004).  Phytochemicals like alkaloids play some metabolic roles and control development in living system (Burkil 1985).
    According to Okwu (2004) saponins prevent disease invasion of plants by parasitic fungi thus, possessing antifungal properties.  Apart from food, yams are mainly used for medical purposes for the sapogenins, aglycons of yam.  Saponins are important mainly because of their steroid structure (Okwu and Ndu 2006).  Yam like higher plants have a complex phytochemical profile (Okwu and Ndu 2006) the most predominant is the presence of Terpenoid, saponin, flavonoid and alkaloid although dioscorine and diosgenin and naturally considered toxic, such toxicity is removed by washing, boiling and cooking (Eka 1998).  The bitterness or acute toxicity in yams may be due to its alkaloid content while saponin and sapogenis may be due to the presence of flavonoids carotanoid (OKwu and Ndu 2006).  However the natural attribute of water yam and white yam necessitated the need for undertaking this study to ascertain the phytochemical (alkaloid, flavonoid, saponin and terpenoid in dioscorea rotundata and dioscorea alata.

1.1    BACKGROUND OF THE STUDY
    Yam are monocotyledonous plants belonging to the genus dioscorea of the family dioscoreaceae dioscorea are import food crops in West Africa and other tropical countries including East Africa, central Africa, South America, South East Asia and India
    The most important area of cultivation and usuage of yam stretches from Ivory Coast through Ghana, Nigeria, Cameroon, Central Africa and Western part of Democratic republic of Congo.
There are about 600 species of dioscorea with more than 10 species cultivated for good and 6 species for pharmaceutical use.
Yam contains many phytochemicals which are non nutritive plant chemical that have protective or disease preventive properties.  These phytochemicals protect human against disease.
There are more than one thousand phytochemical known but only four were tested here (flavonoid, alkaloid, saponin and terpernoid).
1.2    STATEMENT OF PROBLEM
    The phytochecials which has, high medical health benefit cures diseases through consumption of natural food order than drugs which has side effect.
1.3    AIMS AND OBJECTIVES
    This is to identify the phytochemical content in white yam and water yam.  To extract those phytochemicals.  To quantify the phytochemicals in white yam and water yam.
1.4    SCOPE AND LIMITATION
    To identify the phytochemical content in white yam and water yam, the health benefits of this content in human being and quantity to be consumed.  There are many phytochemicals in yams but the research was limited on alkaloid, flavonoid, saponin and terpenoid.
1.5    RESEARCH DESIGN
    This research was carried out by laboratory method collection of sample and blanching.  Pulverization and solvent extraction, quantification and result analysis.
1.6    SIGNIFICANCE OF THE STUDY
    To gain practical experience
    To determine phytochemicals and their health benefits
    Developing our knowledge concerning the importance and health benefit of water yam and white yam