Antinociceptive activity of carvacrol (5-isopropyl-2- methylphenol) in mice

Objectives Carvacrol (5-isopropyl-2-methylphenol) is a monoterpenic phenol which is present in the essential oil of oregano and thyme.We have investigated the behavioural effects of carvacrol in animal models of pain, such as acetic acidinduced abdominal constriction, formalin and hot-plate tests in mice. The spontaneous motor activity of animals treated with carvacrol was investigated using open-field and rotarod tests. Methods Carvacrol was administered orally, at single doses of 50 and 100 mg/kg while indometacin (5 mg/kg), morphine (7.5 mg/kg) and diazepam (2 mg/kg) were used as standard drugs. Naloxone (1 mg/kg) and l-arginine (150 mg/kg) were used to elucidate the possible antinociceptive mechanism of carvacrol on acetic acidinduced abdominal constriction and formalin tests. Key findings The results showed that carvacrol produced significant inhibitions on nociception in the acetic acid-induced abdominal constriction, formalin and hotplate tests. In the open-field and rotarod tests carvacrol did not significantly impair the motor performance. The effect of the highest dose of carvacrol in mice in the acetic acid-induced abdominal constriction and formalin tests were not reversed by naloxone or l-arginine. Conclusions Based on these results, it has been suggested that carvacrol presents antinociceptive activity that may not act through the opioid system nor through inhibition of the nitric oxide pathway