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THE PHYTOCHEMICAL CONSTITUENTS OF METHANOLIC EXTRACT OF OCIMUM GRATISSIMUM

CHAPTER ONE

INTRODUCTION

1.1     Background of the Study

Plants show enormous versatility in synthesizing complex materials which have no immediate obvious growth or metabolic functions. These complex materials are referred to as secondary metabolites. Plants secondary metabolites have recently been referred to as phytochemicals. Phytochemicals are naturally occurring and biologically active plant compounds that have potential disease inhibiting capabilities. It is believed that phytochemicals may be effective in combating or preventing disease due to their antioxidant effect (Halliwell and Gutteridge, 1992; Farombi et al., 1998).

Antioxidants protect other molecules (in vivo) from oxidation when they are exposed to free radicals and reactive oxygen species which have been implicated in the aetiology of many diseases and in food deterioration and spoilage (Halliwell and Gutteridge, 1992; Kasaikina, 1997; Farombi, 2000; Koleva et al., 2000). Medicinal plants have been used for centuries before the advent of orthodox medicine. Leaves, flowers, stems, roots, seeds, fruit, and bark can all be constituents of herbal medicines. The medicinal values of these plants lie in their component phytochemicals, which produce dedefinite physiological actions on the human body. The most important of these phytochemicals are alkaloids, tannins, flavonoids and phenolic compounds (Hill, 1952). Ocimum gratissimum Linn (Labiatae) is grown for the essential oils in its leaves and stems. Eugenol, thymol, citral, geraniol and linalool have been extracted from the oil (Sulistiarini, 1999). Essential oils from the plant have been reported to possess an interesting spectrum of antifungal properties (Dubey et al., 2000).

The antinociceptive property of the essential oil of the plant has been reported (Rabelo et al., 2003). The whole plant and the essential oil are used in traditional medicine especially in Africa and India. The essential oil is also an important insect repellant. O. gratissimum is germicidal (Nakamura et al., 1999; Pessoa et al., 2003; Holets et al., 2003) and has found wide use in toothpastes and mouth washes as well as some topical ointments. It is used as an excellent gargle for sore throats and tonsillitis. It is also used as an expectorant and a cough suppressant. The plant extract is used against gastrointestinal helminths of animals and man (Fakae, 2000; Chitwood, 2003). In addition, O. gratissimum carminative properties make it a good choice for upset stomach. It is used as an emetic and for hemorrhoids. The plant is also used for the treatment of rheumatism, paralysis, epilepsy, high fever, diarrhea, sunstroke, influenza, gonorrhea and mental illness (Dhawan et al., 1977; Oliver, 1980; Abdulrahman, 1992; Osifo 1992; Sofowora, 1993; Sulistiarini, 1999). In addition, the plant is used as a spice and condiment in the southern part of Nigeria.

Medicinal plants based drugs owe the advantage of being simple, effective and exhibit broad spectrum activity. The revival of interest in the use and importance of African medical plants by WHO and many developing countries has led to intensified efforts on the documentation of ethnomedical data of medicinal efforts. This is because most traditional healers keep no records and their information is passed on mainly verbally from generation to generation. Researchers are increasingly turning their attention to natural products looking for new leads to develop better drugs against cancer, as well as