Higher plant are rich source of medicinally important compounds which can be inhanced by plant tissue culture technique.. The useful natural products are synthesized through secondary metabolism, hence they are also known as secondary metabolites. During metabolism in growing cells, the secondary metabolites are either deposited in vacuoles or excreted from gland cells. Large scale yield of secondary metabolites from cultured plant cells can be increased simply by changing the physiological and biochemical conditions from growth medium. The present work was carried out to enhance the production of medicinally important sec. metabolites by using different protocols like precursors,intermediate compounds,of biosynthetic pathway,biotic and abiotic ellicitors. In the present study we have used medicinal plants like Allium cepa(Liliaceae),Trachyspermum ammi(Umbellifereae),Helipterum roseum(Compositeae),Cajanun cajan (Leguminoseae) and Tylophora indica(Asclepeadaceae) as experimental system.The study relates to the isolation,identification,characterization and also enhancement of bioactive principal of these medicinal plants in vitro tissue culture in vitro bioassay were also done.