Loureirin A (50 μM, 100 μM) inhibits collagen-induced platelet ATP secretion and thrombin-stimulated P-selectin expression in a dose-dependent manner. Loureirin A also significantly impairs platelet spreading on immobilized fibrinogen. Loureirin A almost completely eliminates collagen-induced Akt phosphorylation at Ser473 at the dose of 100 μM, and has an additive inhibitory effect with the phosphoinositide 3-kinase (PI3K) inhibitor Ly294002 on collage-induced Akt phosphorylation in platelets at 50 μM.