CHAPTER ONE
INTRODUCTION
1.1  Background of the Study
Phytochemicals are compounds that occur naturally in plants. They contribute to the color, flavour, and smell of plants. In addition, they form part of a plant’s natural defence mechanisms against diseases. Their therapeutic values to human health and disease prevention have been reported (Okwu, 2004)
Pawpaw (Carica papaya) is a plant that belongs to the family of caricaceae. It is a herbaceous succulent plant with self-supporting stems. Elizabeth (1994) has   reported that unripe pawpaw fruits has therapeutic potential on patients with ulcer and impotence. Pawpaw plants produce natural compounds (Annonaceous acetogenins) in leaf bark and twig tissues that posses both highly anti-tumor and pesticide properties. It has been suggested that a potentially lucrative industry based simply on production of plant biomass could develop for production of anti-cancer drugs, pending food and Drug Agency approval, and natural pesticides. The high level of natural self-defence compounds in the plant makes it highly resistant to insect and disease infestation. Pawpaw leaf extract has been reported as a tumor-destroying agent (Walter, 2008).
Fresh green papaw leaf possesses antiseptic properties, while the brown, dried leaf can serve as a tonic and blood purifier. Chewing the seeds of ripe pawpaw has a therapeutic value due to its antiseptic quality. It cleans the intestines from bacteria, more so that only a healthy intestine is able to absorb vitamin and minerals, especially vitamin B12. Tea, prepared with the green papaya leaf, promotes digestion and aids in the treatment of ailments such as chronic indigestion, overweight, obesity, arteriosclerosis, high blood pressure and weakening of the heart (Mantok, 2005). Although there is sufficient information on the phytochemical constitutes of the fruits, there is scarcity of such information on the leaves.
Biter Kola (Garcinia cola) is also known as an Africa wonder nut.  It comes from Garcinia cola trees, which belong to the family of Clusiaceas and it grows in the coastal rainforests in the south western and south Eastern parts of Nigeria. Traditionally these nuts   were chewed as a masticatory substance, to stimulate the flow of saliva (Leakey, 2001) but are now widely consumed as snack in West and central Africa. The kernels of the nuts are widely traded and eaten as a stimulant. Bitter kola is believed to clean the digestive system, without side effects such as abdominal problems, even when a lot of the nuts are eaten. In folk, G. Kola is used in folklore remedies for the treatment of ailments such as liver disorders, hepatitis, diarrhea laryngitis, bronchitis and gonorrhea (Iwu, 1993). The seed is masticatory and also used to prevent and relieve colic, chest colds, cough and can as well be used to treat headache. This plant can be used for the treatment of jaundice, high fever and as a purgative. The plant is also found useful in the treatment of stomach ache and gastritis.
The phytochemical compounds isolated from G. Kola include Oleoresin, tannins, saponins, alkaloids cardiac glycosides. Other phytochemical compounds so far isolated from G. Kola seeds are biflavonoids such as kola flavone and 2-hydroxybi-flanoids (Okunji et al, 2002). However, there is paucity of such information on the leaves.