4.4. Platelet Aggregation in Plasma-Rich Platelets (PRP)

The effect of phenolic compounds on platelet aggregation against PAF, ADP, and TRAP (Thrombin analogue) was determined on plasma-rich platelets (PRP) from healthy volunteers. The molecules were dissolved in DMSO (1.6% maximum DMSO final concentration). Platelet count of PRP was adjusted to 300.000/mL with PPP. Samples were incubated at 37 °C, with a stirring rate of 1.000 rpm. A Chronolog Aggregometer (Model 440VS) was used for determining aggregation responses based on the light transmittance method against various concentrations of PAF, ADP, and thrombin receptor-activating peptide (TRAP), a PAR-1 (Protease-Activated Receptor) selective activating peptide. Optical aggregation results were expressed as a percentage of aggregation at a given time interval from agonist addition; aggregation was defined as the difference between the 0% (PRP) baseline and the 100% (PPP) baseline. The aggregation was induced by final concentration of PAF ranging between 1–4 μM (dissolved in bovine serum albumin 2.5 mg/mL), of ADP ranging between 50–100 μM (dissolved in saline) and of TRAP ranging between 4–7 μM (dissolved in saline) with respect to each volunteer. In addition, 0% inhibition was considered as platelet aggregation without the addition of the examined compound. The plot of percentage inhibition (ranging from 20% to 80%) vs. different concentrations of the examined compound is linear and it was used to calculate the concentration of the sample that induced 50% inhibition against each agonist. This value was defined as the IC₅₀, namely, inhibitory concentration producing 50% inhibition.