**1. Introduction**

Coumarins are members of the benzopyrone class of organic compounds that are found in many plants [1] and possess a variety of pharmacological properties such as antimicrobial, anti-inflammatory, antidiabetic, and antioxidant activity, as well as a significant influence on physiological processes like enzyme inhibitory activity [2]. Despite the wide availability of coumarins and their lead compounds and metabolites in natural products [3], their application up till now has been mostly limited to the anticoagulant activity of warfarin derived from dicoumarol and its analogues [4]. The mechanism of action of these anticoagulants lies in the competitive antagonism of vitamin K, through which they inhibit coagulation of blood in the body by preventing the production of prothrombin and several other coagulation factors [5]. Due to this action, these coumarins are a major group of oral drugs with anticoagulant activity. Anticoagulants reduce the risks of undesirable

blood clots leading to myocardial infarction, pulmonary embolism, and ischemic stroke among others. This chapter gives an overview of medical applications of coumarins, in particular the history and evolution of warfarin and related compounds as important anticoagulant agents.
