Eugenol: a dual inhibitor of platelet-activating factor and arachidonic acid metabolism

• Published in: Phytomedicine (Stuttgart) 1995-07, Vol.2 (1), p.23-28
• Main Authors: Saeed, S.A., Simjee, R.U., Shamim, G., Gilani, A.H.
• Format: Article
• Language: English
• Subjects: anti-inflammatory; arachidonic acid; Eugenol; inhibitor; platelet aggregation; platelet-activating factor
• ISSN: 0944-7113; 1618-095X
• DOI: 10.1016/S0944-7113(11)80044-9

Eugenol is an active principal and responsible for several pharmacological activities of clove oil. We studied the effects of eugenol on human platelet aggregation, arachidonic acid (AA) and platelet-activating factor (PAF) metabolism and in vivo effects on AA and PAF-induced shock in rabbits. Eugenol strongly inhibited PAF-induced platelet aggregation with lesser effect against AA and collegen. The IC 50 values were against AA: 31 ± 0.5; collagen: 64 ± 0.7 and PAF 7 ± 0.2 μM (n=9) respectively. In addition, eugenol stimulated PAF-acetylhydrolase activity suggesting that inhibition of PAF could be due to its inactivation to lyso-PAF. Pretreatment of rabbits with eugenol (50–100 mg/kg) prevented the lethal effects of intravenous PAF (11 μgg/kg) or AA (2 mg/kg) in a dose-dependent fashion. The protective effects of eugenol in the rabbits, however, were more pronounced against PAF-induced mortality (100% protection). In addition, eugenol also inhibited AA metabolism via cyclooxygenase and lipoxygenase pathways in human platelets. Both the production of thromboxane-A 2 and 12-hydroxy-eicosatetraenoic acid was inhibited by eugenol in a concentration-related manner (30–120 μM). In vivo, eugenol (50–100 mg/kg; i.p.) inhibited carrageenan-induced rat paw oedema (P < 0.001). In this test, eugenol was 5 times more potent than aspirin. These results provide evidence that eugenol acts as a dual antagonist of AA and PAF.