Antioxidative and antiplatelet effects of aqueous inflorescence Piper betle extract

Piper betle, belonging to the Piperaceae family, is a tropical plant, and its leaf and inflorescence are popularly consumed by betel quid (BQ) chewers in Taiwan and many other South and Southeast Asian countries. However, little is known about the biochemical properties of inflorescence Piper betle (IPB) toward reactive oxygen species (ROS) and platelet functions. In the present work, aqueous IPB extract was shown to be a scavenger of H2O2, superoxide radical, and hydroxyl radical with a 50% inhibitory concentration (IC50) of about 80, 28, and 73 mug/mL, respectively. IPB extract also prevented the hydroxyl radical induced PUC18 plasmid DNA breaks at concentrations higher than 40 mug/mL. Since ROS are crucial for platelet aggregation, we further found that IPB extract also inhibited the arachidonic acid (AA) induced and collagen-induced platelet aggregation, with an IC50 of 207 and 335 mug/mL, respectively. IPB extract also inhibited the AA-, collagen- (>100 mug/mL of IPB), and thrombin (>250 mug/mL of IPB)-induced thromboxane B-2 (TXB2) production by more than 90%. However, IPB extract showed little effect on thrombin-induced aggregation. These results indicated that aqueous components of IPB are potential ROS scavengers and may prevent the platelet aggregation possibly via scavenging ROS or inhibition of TXB2 production.