Coffee extracts inhibit platelet aggregation in vivo and in vitro

The effect of aqueous coffee extracts on platelet aggregation in humans (in vitro) and rabbits (both in vitro and in vivo) was investigated. Coffee extracts were found to have anti-aggregatory effects on in vitro platelet aggregation induced by ADP or arachidonate but not by collagen. Coffee extracts were also effective after intravenous administration in rabbits. The compound(s) responsible for these effects are water-soluble, heat-resistant, appeared to be different from salicylates, and might also be due to unidentified compounds besides nicotinic acid or known xanthines. Coffee extract and selected fractions decreased the conversion of [14C]-arachidonic acid to thromboxane B2 by the platelets. These studies show that coffee extracts contain compounds which are active in inhibiting platelet aggregation, a critical step involved in thrombosis and other vascular disorders.