Extracts of feverfew inhibit granule secretion in blood platelets and polymorphonuclear leucocytes.

Extracts of feverfew (Tanacetum parthenium) inhibited secretory activity in blood platelets and polymorphonuclear leucocytes (PMNs). Release of serotonin from platelets induced by various aggregating agents (adenosine diphosphate, adrenaline, sodium arachidonate, collagen, and U46619) was inhibited. Platelet aggregation was consistently inhibited but thromboxane synthesis was not. Feverfew also inhibited release of vitamin B12-binding protein from PMNs induced by the secretagogues formyl-methionyl-leucyl-phenylalanine, sodium arachidonate, and zymosan-activated serum. Feverfew did not inhibit the secretion induced in platelets or PMNs by the calcium ionophore A23187. The pattern of the effects of the feverfew extracts on platelets is different from that obtained with other inhibitors of platelet aggregation and the effect on PMNs is more pronounced than has been obtained with very high concentrations of non-steroidal anti-inflammatory agents.