Inhibitory effect of eugenol on rat ileal motility in vitro

Abstract

Eugenol, an essential oil of clove oil possesses several different pharmacological properties, including antimicrobial, antifungal, insecticidal and antihelmintic. With regard to the digestive tract, eugenol has shown spasmolitic and relaxant effects. To elucidate some of the mechanisms involved, the effects of eugenol on contractions of isolated rat ileum induced by electrical field stimulation (EFS) were investigated. Eugenol (100 µM) significantly and reversibly reduced EFS induced contractions by approximately 80%. Control contractions were 2.00±0.18 g, while contractions in the presence of eugenol decreased to 0.40±0.02 g (n=7; P=0.0001), respectively. Moreover, eugenol (100 µM) reversibly decreased ileal basal tonus from 0.88±0.04 g to 0.65±0.04 g (n=7; P=0.0002). After incubation with the nitric oxide synthase inhibitor nitro-Larginine methyl ester (L-NAME), eugenol (100 µM) still significantly inhibited ileum contractions (reduction by 75.30%), from 1.70±0.09 g to 0.42±0.08 g (n=6; P=0.0001), respectively. Likewise, incubation with L-NAME did not alter the eugenol relaxant effect on ileal basal tonus. Mean control basal tonus was 0.84±0.07 g and significantly decreased after the addition of eugenol (100 µM), to 0.37±0.09 g (n=6; P=0.0003). After incubation with 300 µM of L-NAME mean basal tonus was 0.85±0.08 g, while eugenol significantly relaxed ileal preparations in the presence of L-NAME to 0.34±0.11 g (n=6; P=0.0003). Our results suggest that eugenol reversibly inhibits contractions caused by EFS and induces relaxation of rat ileum via a mechanism largely independent of NO activity.