Inhibition of platelet aggregation and 5-HT release by extracts of Australian plants used traditionally as headache treatments

To identify potential migraine therapeutics, extracts of eighteen plants we re screened to detect plant constituents affecting ADP induced platelet agg regation and [C-14]5-hydroxytryptamine (5-HT) release. Extracts of the seve n plants exhibiting significant inhibition of platelet function were reanal ysed in the presence of polyvinyl pyrrolidone (PVP) to remove, polyphenolic tannins that precipitate proteins. Two of these extracts no longer exhibit ed inhibition of platelet activity after removal of tannins. However, extra cts of Crataegus monogyna, Ipomoea pes-caprae, Eremophila freelingii, Eremo phila longifolia, and Asteromyrtus symphyocarpa still potently inhibited AD P induced human platelet [C-14]5-HT release in vitro, with levels ranging f rom 62 to 95% inhibition. I. pes-caprae, and C. monogyna also caused signif icant inhibition of ADP induced platelet aggregation. All of these plants h ave been previously used as traditional headache treatments, except for C. monogyna which is used primarily for protective effects on the cardiovascul ar system. Further studies elucidating the compounds that are responsible f or these anti-platelet effects are needed to determine their exact mechanis m of action. (C) 2000 Elsevier Science B.V. All rights reserved.