Anti-inflammatory effects of Rosmarinus officinalis essential oil in mice

Abstract

Essential oils are plant secondary metabolites possessing various pharmacological properties, primarily anti-oxidative, antimicrobial or immunomodulative, but they can exhibit toxic and allergic effects as well. The aim of this study was to compare the effects of Rosmarinus officinalis essential oil dietary administration in carrageenan paw oedema and trinitrobenzene sulfonic acid (TNBS) colitis. ICR mice received rosemary essential oil at three concentrations (1 250, 2 500 and 5 000 ppm) in the standard laboratory diet starting two weeks before the experiments. The inflammation of paws induced by carrageenan application was evaluated by measurement of paw swelling, paw weight and myeloperoxidase activity. In the TNBS model the mice were killed by cervical dislocation 3 days after colitis induction and the mortality, changes in the body weight of mice, colon weight : body weight ratio, macroscopical scores and myeloperoxidase activity were analysed. Furthermore, IL-1β and IL-6 cytokine levels in colonic tissue were quantified using ELISA assay. Dietary supplementation with 5 000 ppm of rosemary essential oil initially after 2 h increased but after 24 h suppressed the extent of paw oedema. The same dose in the TNBS model exhibited protective effects on colonic mucosa and significantly decreased macroscopic scores for colonic inflammation. On the other hand, in colon samples from mice fed the diet with 1 250 ppm of rosemary essential oil we detected decreased myeloperoxidase activity and significantly lower levels of IL-6 compared to TNBS control animals. Our results indicate that rosemary essential oil is able to influence several variables of murine experimental inflammatory models depending on the concentration used. We conclude that the anti-inflammatory effects of rosemary essential oil should be interpreted carefully due to its timeand dose-related effects.