Abstract

Thrombotic disorders remain a leading cause of morbidity and mortality, necessitating the search for novel antiplatelet agents with favorable safety profiles. This study investigates the mechanism by which the polymethoxylated flavonoid, Nobiletin, exerts its antiplatelet effect, focusing on its interaction with the platelet membrane-bound A2A Adenosine Receptor (A2AAR). The A2AAR is a G-protein coupled receptor known to inhibit platelet activation by elevating intracellular cyclic adenosine monophosphate (cAMP) levels. Using human washed platelets, we demonstrated that Nobiletin significantly inhibits agonist-induced platelet aggregation and secretion. Crucially, this inhibitory effect was completely abolished by the selective A2AAR antagonist, SCH 58261, confirming the receptor's central role. Further biochemical analysis revealed that Nobiletin acts as an agonist, leading to a robust, dose-dependent increase in intracellular cAMP concentration, which is a key second messenger in the anti-aggregatory signaling cascade. These findings establish a clear membrane-level mechanism for Nobiletin's action, identifying it as a novel, naturally-derived A2AAR activator. The study highlights Nobiletin's potential as a promising therapeutic candidate for the prevention and treatment of cardiovascular diseases by targeting a critical regulatory pathway on the platelet cell surface.