The primary role of medicinal chemist has become one of improving upon existing drugs by increasing their potency and duration of action and by decreasing toxic side effects as well as creating new drugs by molecular modifications. Very useful synthetic analogue with improved therapeutic properties can be obtained from a single lead compound by structural modification. The same applies to the group of natural lactone of plant origin, one of the diverse and important system of natural products with a broad spectrum biological activities. Physiological activity of natural lactone is known ever since santonine was used as anthelmintic and ascarisidal agent. The biological importance of unsaturated lactone is well known. The butenolide system is present in many cardiac glycosides shows strong cardiotonic activity. In particular, the -alkylidene butenolide skeleton is a useful entity that is present natural products such as fibrolides, dihydroxerulin and protoanemonin. Protoanemonin and its analogues possess antiviral, antibiotic and anticancer activities."

Several sulphur & nitrogen containing heterocyclic compounds have been studied because of their interesting biological properties such as Anti-bacterial, Anti-fungal, Anti-hypertensive, Anti-HIV, Anti-inflammatory, Anti-microbial, Anti-rheumatic, Aldose reductase inhibitor, ATP-sensitive potassium channel opener. 1,4-Benzothiazine forms an important class of heterocyclic system. Several studies are available for 1, 4-Benzothiazine formation and their application in drugs. 1, 4-benzothiazine and thiazoles constitute an important class of sulfur and nitrogen heterocytes. The utility of thiazole as medicaments is finally established. Recently that attention is being directed towards the synthesis of 1,4-benzothiazine, as they are structurally analogues to phenothiazine nucleus. Luciferin and rifamycin are 1,4-benzothiazine derivatives and are obtained by biosynthesis and found to posses immense pharmacological activities and also have application is dyestuff, photographic developer, UV light absorber and antioxidants.

India has a rich heritage of knowledge on plant based drugs used in traditional system of medicine. A large number of plants and remedies were pharmacologically tested and useful data was generated for development of therapeutic agents. Scientists are searching newer avenues and material for drug development and for that they are search for new medicinal plants, which are till date not have been exploited to their fullest extent (except traditional systems). The rich biodiversity of the tropical region all over the world have attracted scientific attention and tropical region of lower plane land of West Bengal is not an exception of that trend. Hygrophila difformis is a tropical plant, accordingly in our laboratory we have chosen this plant for the detail pharmacological studies to fulfill our quench of thirst and to reveal whether this plant could be utilized as an effective source for future medicine development. In the course of the investigation it was found that the methanolic fraction of the Hygrophila difformis leaf extract possesses various kinds of activities.