NQ301, an antithrombotic agent, inhibits collagen-challenged rabbit platelet aggregation (IC50: 10 mg/mL).

NQ301 dose-dependently inhibits collagen (10 mg/mL, IC50: 0.60±0.02 μM), U46619 (1 mg/mL, IC50: 0.58±0.04 μM) and arachidonic acid (100 mg/mL, IC50: 0.78±0.04 μM) challenged rabbit platelet aggregation. NQ301 potently suppresses thromboxane B2 formation by platelets that are exposed to arachidonic acid in a concentration-dependent manner, but had no effect on the production of prostaglandin D2, indicating an inhibitory effect on thromboxane A2 synthase. NQ301 markedly inhibits the increase of cytosolic Ca2+ concentration and ATP secretion, and also markedly increases platelet cAMP levels in the activated platelets. The antiplatelet activity of NQ301 may be mediated by inhibition of cytosolic Ca2+ mobilization, enhancement of cAMP production and inhibition of ATP secretion in activated platelets.

Compounds are dissolved in DMSO (5 mg/mL) and diluted with PBS/EtOH (70:30).Kinetic analyses are carried out for TB5 and TB8. A set of Lineweaver–Burk plots are constructed in the absence and presence of various concentrations of compounds TB5 and TC8. The set consists of five graphs, each constructed by measuring MAO-B and MAO-A catalytic rates at different substrate concentrations (0.1-1 μM). The first Lineweaver–Burk plot is constructed in the absence of inhibitor, while the remaining four graphs are constructed in the presence of different concentrations of TB5 and TB8[1].

ished rabbit platelet suspension is challenged by addition of collagen (10 mg/mL), arachidonic acid (100 μM) or U46619 (1 μM). Concentration- response relationship is determined in the absence or presence of a range of concentrations of NQ301 (0, 0.25, 0.5, 0.75, 1 μM); aspirin-treated platelets (50 μM for 5 min) are used to prevent any possible contribution of endogenous arachidonic acid metabolites to platelet aggregation. The resulting aggregation, measured as the change in light transmission, is recorded for 5 min. The extent of platelet aggregation is expressed as % of the control[1].