ANTIPLATELET PRINCIPLES FROM A FOOD SPICE CLOVE (SYZGIUM-AROMATICUM L)

In continuation of our studies on the oil of cloves - a common kitchen spice and a drug for home medicine - we have isolated and identified two antiplatelet components, eugenol and acetyl eugenol. They inhibite d arachidonate-, adrenaline- and collagen-induced platelet aggregation ; they were more potent in inhibiting aggregation by the first two ago nists. Their inhibitory effect was reversible. These components were a ntiaggregatory by a combination of at least two effects: (i) inhibitio n of platelet thromboxane formation, and (ii) increased formation of 1 2-lipoxygenase products (12-HPETE). Though the presence of plasma prot eins would reduce the effective concentration of these substances due to binding, the relatively lower amounts of these components which inh ibited arachidonate-induced aggregation when compared to their effects on thromboxane production was intriguing. The answer might partly lie in an increased formation of 12-HPETE facilitated by albumin which ac ts as a 'conduit' to divert free arachadonic acid (AA) from the platel et cyclooxygenase (CO) to the lipoxygenase pathway (22). Based on thei r IC50 values, it was found that both eugenol and acetyl eugenol were more potent than aspirin in inhibiting platelet aggregation induced by arachidonate, adrenaline and collagen. In arachidonate-induced aggreg ation eugenol was on a par with indomethacin. It was found that eugeno l and acetyl eugenol when used in-combination potentiated inhibition o f platelet aggregation induced by arachidonate, adrenaline and collage n. This effect was, however, not evident from the metabolism of AA in platelets; when used in combination the two compounds produced an addi tive effect.