An orally bioavailable, glucoside derivative of the flavonoid quercetin and protein disulfide isomerase (PDI) inhibitor, with antioxidant and potential antithrombotic activity. As an antioxidant, isoquercetin scavenges free radicals and inhibits oxidative damage to cells. As a PDI inhibitor, this agent blocks PDI-mediated platelet activation, and fibrin generation, which prevents thrombus formation after vascular injury. In addition, isoquercetin is an alpha-glucosidase inhibitor. PDI, an oxidoreductase secreted by activated endothelial cells and platelets, plays a key role in the initiation of the coagulation cascade. Cancer, in addition to other thrombotic disorders, increases the risk of thrombus formation.