Regular Article Effective anti-platelet and COX-1 enzyme inhibitors from pungent constituents of ginger Effie Nurtjahja-Tjendraputra, Alaina J. Ammit, Basil D. Roufogalis, Van H. Tran, Colin C. Duke * Herbal Medicines Research and Education Center, Faculty of Pharmacy, University of Sydney, NSW 2006, Australia Received 15 April 2003; received in revised form 18 August 2003; accepted 16 September 2003 Abstract Background: Based on recent studies, pungent constituents of ginger (Zingiber officinale) and related substances represent a potential new class of anti-platelet agents. The ability of 20 pungent constituents of ginger and related substances to inhibit arachidonic acid (AA) induced platelet activation in human whole blood was studied. Methods: Anti-platelet activity of the compounds was measured in vitro by the Chrono Log whole blood platelet aggregometer. Molecular hydrophobicity (log P) was measured by reversed-phase high-performance liquid chromatography. COX-1 (ovine) inhibitory effect of [8]-paradol and analogues 1 and 5 was carried out using a COX-1 inhibitor assay kit. Results: [8]-Gingerol, [8]-shogaol, [8]-paradol and gingerol analogues (1 and 5) exhibited anti-platelet activities with IC 50 values ranging from 3 to 7 AM, whilst under similar conditions the IC 50 value for aspirin was 20 F 11 AM. The COX-1 inhibitory activity of [8]-paradol (IC 50 =4 F 1 AM) was more potent than the gingerol analogues (1 and 5) (IC 50 approximately 20 AM). Conclusion: The above findings show that gingerol compounds and their derivatives are more potent anti-platelet agents than aspirin under the conditions described in this study. [8]-Paradol, a natural constituent of ginger, was found to be the most potent COX-1 inhibitor and anti platelet aggregation agent. The mechanism underlying AA-induced platelet aggregation inhibition may be related to attenuation of COX-1/Tx synthase enzymatic activity. Lastly, important features of phenolic compounds for inhibition of AA-induced platelet aggregation and COX-1 activity were revealed in this study. D 2003 Elsevier Ltd. All rights reserved. Keywords: Aspirin; Ginger; Arachidonic acid; Platelet aggregation; Cyclooxygenase-1; Human whole blood Platelets are the smallest components in the blood stream, where they exist as a-nucleate disc-shaped cells in their resting state and travel singly as discoidal particles [1– 3]. In the presence of stimuli such as arachidonic acid, activated platelets change shape into spiny spheres. They bind to fibrinogen, aggregate and release the contents of their intracellular granules, including adenosine diphosphate (ADP) and serotonin [1–3]. ADP and an arachidonic acid (AA) metabolite acting an endogenous platelet activator, thromboxane A 2 (TxA 2 ), intensify the extent of platelet aggregation. These substances act in positive feedback loops, making platelet aggregation an autocatalytic rather than equilibrium response [4]. Under pathophysiological conditions, platelet activation may result in peripheral, cardiovascular or cerebrovascular thrombosis with serious consequences. Inhibition of cyclooxygenase (COX-1) enzyme activity, by inhibitors such as aspirin, greatly reduces the production of TxA 2 and subsequently inhibits platelet aggregation and the formation of the platelet plug [4]. Although an effective drug, aspirin usage is associated with potentially life-threat- ening side effects such as gastric haemorrhage [4]. Thus, researchers have been encouraged to investigate and ulti- mately develop new anti-platelet medicinal agents that are equivalent in strength to aspirin, but with less or no adverse events. Ginger, the rhizome of Zingiber officinale, is a traditional medicine with a carminative effect and anti-nausea action. 0049-3848/$ - see front matter D 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.thromres.2003.09.009 Abbreviations: AA, arachidonic acid; ASA, aspirin; COX-1/Tx, cyclo- oxygenase-1/thromboxane; TxA 2 , thromboxane A 2 ; SAR, structure – activity relationship; log P, logarithm of octanol– water partition coefficient; G, gingerols; S, shogaols; P, paradols; Gd, gingerdiols. * Corresponding author. Tel.: +61-2-93512321; fax: +61-5-93514391. E-mail address: colind@pharm.usyd.edu.au (C.C. Duke). Thrombosis Research 111 (2003) 259 – 265