Maintenance and achievement of an optimal platelet function by dietary solutions might be considered an interesting target to influence cardiovascular health. Polyphenol-rich foods such as vegetables and fruits have been shown to significantly improve platelet function in ex vivo studies in humans. However, until yet, it still remains unclear if polyphenols itself, their metabolites or a mixture of both are responsible for the beneficial effects observed so far. Our study aims to evaluate the effect of anthocyanins, in vivo metabolites of different polyphenols from colonic origin and a representative mixture of both at physiological concentrations on platelet aggregation and activation function. Some anthocyanins [1 microM], colonic metabolites [10 microM] and a mixture (4 phenolic acid [1 microM], 4 anthocyanin [0.1 microM] showed significant platelet sedating and desensitizing effects. Activation of the platelets (P-selectin expression) was significantly reduced by 10-40% in resting platelets, TRAP-activated and hydrogen peroxide-stressed platelets and epinephrine pre-activated platelets relative to controls. The dose-response curve of the weak agonist TRAP was also significantly altered resulting in a >0.8 microM increase of threshold concentration to induce aggregation. The representative mixture was active despite ten times lower concentrations of the individual components, which showed no activity when tested individually at that concentration, indicating synergism of the different components. Platelet reactivity to strong agonists such as collagen and ADP was not influenced. These results show that anthocyanins and in vivo metabolites of polyphenols have anti-thrombotic properties, suggesting themselves as well as their dietary sources and precursors as potential cardiovascular health promoters.