The history of natural products is as ancient as human being and these are used to cure man since life started. Drugs either isolated or derivative of natural products has played a great role in pharmaceutical industries and specially obtained from plants. Plants have provided us some of the very important life saving drugs used in the armamentarium of modern medicine. The exploration of the chemical constituent of the plants and pharmaceutical screening may provide us the basis for developing the lead for development of novel agents. Among the estimated 400,000 plant species, only 6% have been studied for biological activity and about 15% have been investigated phytochemically. This inadvertently shows a need for the in-depth dissertation of various chemical constituents, medicinal viability, biological and pharmacological evaluation of plants. The Part A of the present Ph. D thesis deals with isolation of bioactive constituents from a medicinally important plant of Pakistan namely Fraxinus xanthoxyloides. The search for the new chemical agents is one of the most challenging tasks for the medicinal chemist. Similarly, the synthesis of high nitrogen containing heterocyclic systems has been attracting and increasing interest among the scientists over the past decade because of their utility in daily life. In recent years, the chemistry of triazoles and their fused heterocyclic derivatives has received considerable attention owing to their synthetic and effective biological importance. The presence of three nitrogen hetero-atoms in five membered ring systems defines an interesting class of compounds, the triazole. Therefore, the present thesis is presented in the following two parts. Part A Studies on the Chemical Constituents of Fraxinus xanthoxyloides Part B Synthesis, Characterization and Biological Evaluation of Substituted Triazoles