Eugenol suppresses cyclooxygenase-2 expression in lipopolysaccharide-stimulated mouse macrophage RAW264.7 cells

Inducible cyclooxygenase (COX-2) has been implicated in the processes of inflammation and carcinogenesis. Thus, the potential COX-2 inhibitors have been considered as anti-inflammatory or cancer chemopreventive agents. In this study, the methanolic extract of the cortex of Eugenia caryophyllata Thunberg (Myrtaceae) was found to potently inhibit the prostaglandin E-2 production in lipopolysaccharide (LPS)-activated mouse macrophage RAW264.7 cells (98.3% inhibition at the test concentration of 10 mug/ml). Further, hexane-soluble layer was the most active partition compared to ethyl acetate, n-butanol, and water-soluble parts. By bioassay-guided fractionation of hexane-soluble partition, eugenol was isolated and exhibited a significant inhibition of PGE(2) production (IC50 = 0.37 muM). In addition, eugenol suppressed the cyclooxygenase-2 (COX-2) gene expression in LPS-stimulated mouse macrophage cells. On the line of COX-2 playing an important role in colon carcinogenesis further study was designed to investigate the effect of eugenol on the growth and COX-2 expression in HT-29 human colon cancer cells. Eugenol inhibited the proliferation of HT-29 cells and the mRNA expression of COX-2, but not COX-1. This result suggests that eugenol might be a plausible lead candidate for further developing the COX-2 inhibitor as an anti-inflammatory or cancer chemopreventive agent. (C) 2003 Elsevier Science Inc. All rights reserved.