**1.4. Identification and standardization of active principles in medicinal plants**

Medicinal plants are very rich in chemical compounds which they produce for their own defense and are known as secondary metabolites (phytochemicals) and their medicinal potencies are attributed to these chemical compounds [11]. A medicinal plant may contain a mixture of different phytochemicals, for example, saponins, which have ability to lower cholesterol; alkaloids which are rich in nitrogenous compounds and are stimulants; tannins which are natural antibiotics; anthraquinones used as laxative and dye; cardiac glycosides which are good cardiovascular drugs; and phenols and flavonoids which are rich in antioxidants. The ability to identify these biologically active compounds in a medicinal plant serves as a guide in its quality control and dose determination. Most medicinal plants in Nigeria have not been screened for their complete phytochemical compositions, and this would help in their dose determination and standardization. The entire world has more than 250,000 species of higher plants gathered from conservative studies, and only an insignificant percentage has been exhaustively studied for their potentials as drug sources [11].
