7,4'-Dimethoxy-3-hydroxyflavone is an orally active PAR4 antagonist. This compound inhibits PAR4-mediated human platelet aggregation with an IC50 of 1.4 μM. It disrupts PAR4-mediated aggregation and related signaling pathways, including NF-κB, Ca2+/protein kinase C (PKC), Akt, ERK, and p38. In a streptozotocin (STZ)-induced diabetic mouse model, 7,4'-Dimethoxy-3-hydroxyflavone inhibits vascular PAR4 expression, improves endothelial dysfunction, and reduces oxidative stress. Additionally, it prevents thrombosis in mice without affecting bleeding time.

7,4'-Dimethoxy-3-hydroxyflavone, administered at concentrations ranging from 1 to 10 μM for periods of 6 to 48 hours, inhibits high glucose-induced endothelial PAR4 expression in EA.hy 926 cells, a function not observed with other PAR4 antagonists like 7,4'-dimethoxyflavone (DMF, 10 μM), YD-3 (1 μM), or BMS-986120 (BMS; 1 nM). The compound blocks high glucose-induced endothelial PAR4 activity in these cells by completely inhibiting PAR4-mediated calcium responses and significantly reducing the calcium response to AYPGKF-NH₂ (a PAR4 activating peptide) or thrombin. At 1-10 μM for 24 hours, 7,4'-Dimethoxy-3-hydroxyflavone prevents PAR4-aggravated endothelial dysfunction in a high glucose environment by inhibiting ROS-driven NF-κB activation, subsequently suppressing PAR4 expression. Furthermore, at concentrations of 1-5 μM for 3-5 minutes, it inhibits PAR4-mediated human platelet aggregation and secretion by blocking the activation of GPIIb/IIIa, a critical step in PAR4-activating peptide-induced platelet aggregation. Additionally, at 1-5 μM for 1-3 minutes, it disrupts downstream PAR4 signaling pathways in platelets, including Ca²⁺/protein kinase C, Akt, ERK, and p38. In CHO-K1 cells, concentrations of 5-20 μM for 10 minutes inhibit β-arrestin recruitment to PAR4 in a concentration-dependent manner. At 5-20 μM for 3 minutes, 7,4'-Dimethoxy-3-hydroxyflavone enhances the inhibition effect of Vorapaxar and Ticagrelor on thrombin-induced platelet aggregation. Lastly, at 5-10 μM for 10 minutes, it reduces thrombosis under flow conditions in whole blood.

The compound 7,4'-Dimethoxy-3-hydroxyflavone (DMF-OH), administered orally at a dose of 20 mg/kg daily for 21 days, reduces vascular PAR4 expression, improves endothelial dysfunction, and mitigates oxidative stress damage in a Streptozotocin (STZ)-induced diabetic mouse model. Additionally, a single intraperitoneal dose of 7,4'-Dimethoxy-3-hydroxyflavone (1-7.5 mg/kg) effectively prevents FeCl₃-induced carotid artery occlusion without affecting tail bleeding time.