The present dissertation deals with the isolation and characterization of constituents from two Pakistani medicinal plants and their subsequent biological activities. The isolated compounds were characterized by using various sophisticated spectroscopic techniques. Indigofera hetrantha Wall. belongs to the family Leguminosae and has found diverse medicinal uses in the indigenous systems of medicine. Phytochemical studies on the ethyl acetate soluble fraction of Indigofera hetrantha, collected from Swat (Pakistan), have resulted in the isolation and structure elucidation of five new and four known therapeutic agents. Periploca aphylla Decne. (Asclepiadaceae) occurs in the northern areas of Pakistan and finds various uses in the indigenous system of the medicine. Photochemical studies on the ethyl acetate soluble fraction of Periploca aphylla, collected from Swat (Pakistan), have resulted in the isolation and structure elucidation of three new and six known therapeutic agents.