The work embodied in this book is divided into three parts. Part-A includes the literature based phytochemical studies on the methanolic extract of one of the most significant medicinal herb Iris germanica, which led to the isolation and characterization of the 6 new compounds beside this, 6 known compounds. The oil fraction was also isolated which resulted the identification of eleven compounds. The Part-B includes the biological screening of various plant extracts with special reference to antioxidant activity, microbial activity and toxicity of two compounds and oil fraction. The Part-C discusses literature survey and computational modeling of cis-decalin reaction using Friedel Crafts acylating.