Warfarin primarily exists as the open-chain 4-hydroxycoumarin tautomer in aqueous environments. According to spectroscopic studies, the ionized form of the open-chain tautomer binds with HSA to distribute the drug to the body. The binding study of 3,4,7,8-Tetrahydroxyflavone with HSA indicated that this molecule exists in both keto and enol tautomers; however, in HSA bound complex, both tautomers are deprotonated by releasing proton from hydroxyl group. One of the tautomers has a significant interaction in one of the sites, and another tautomer has a weak interaction in the other site. Overall, the interaction of drugs with human HSA is a complex process and plays a significant role in drug transport, distribution, drug-drug interactions, clearance, and toxicity.