Effects of a Combination of Thyme and Oregano Essential Oils on TNBS-Induced Colitis in Mice

[Crohn2357]

Effects of a Combination of Thyme and Oregano Essential Oils on TNBS-Induced Colitis in Mice
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2233768/

 

[Crohn2357]

From the study:

We applied three doses of thyme and oregano essential oil combination (0.4% thyme and 0.2% oregano oils, 0.2% thyme and 0.1% oregano oils, 0.1% thyme and 0.05% oregano oils) to mice with TNBS-induced colitis, and found that administration of the medium dose decreased the mortality rate from 53% to 33%, significantly accelerated the body weight gain recovery, and significantly reduced the macroscopic damage of the colonic tissue. In animals fed with the two other doses of the essential oils, we did not find a significant improvement in the mortality rate, body weight gain recovery, or colonic tissue damage.

Examination of IL-1β and IL-6 protein expression in our experiment confirmed the best efficacy of the medium dose of thyme and oregano oil combination in the suppression of colitis. The cytokine protein level in animals treated with the medium dose, but not in animals treated with the other two doses, was significantly lower than in the untreated colitic animals. The low effectiveness in attenuating the colitis found after administration of the highest dose of thyme and oregano oil combination could be connected with possible cytotoxic effects of higher concentrations of these oils. In our preliminary experiments with intact mice, we found negative effects of higher concentrations of thyme essential oil (1%) and oregano essential oil (0.5%) on body weight and food intake. Moreover, the cytotoxic effect of higher concentrations of these oils has been demonstrated in intestinal cells and lymphocytes [39, 40]. Thus, the lack of the dose dependency found in this study could be due to a combination of positive and negative effects of the highest concentration of thyme and oregano essential oil combination. On the other hand, too low doses of essential oils can be insufficient to reduce the intensity of inflammation. A similar phenomenon was found in the study examining the protective effects of curcumin on TNBS-induced colitis in mice, where the medium tested dose was more effective at improving body weight gain than the lower or higher doses of curcumin. To explain the lack of the dose dependency, authors speculated about curcumin toxicity or about the influence on the food intake [4]. Thus, the use of optimal doses is essential for good efficacy of essential oils (or their components) in attenuating inflammation. Further experiments are needed to establish the most efficient concentration of thyme and oregano essential oil combination.

In our preliminary experiments (using similar experimental conditions as in the present study), we administered thyme (0.5%, 0.25%, 0.12%) or oregano (0.4, 0.2%, 0.1%) essential oil alone in diet to mice with TNBS-induced colitis and we found no significant positive effect. Furthermore, we observed negative effects on body weight and food intake with oregano at 0.4% concentration. However, we observed a better recovery of body weight after treatment with a combination of these essential oils in preliminary tests. The results of the present study confirm the positive effects of the combined administration of appropriate concentrations of thyme and oregano oils on TNBS-induced colitis. It is known that oregano essential oil possesses strong antimicrobial activity, which is ascribed to carvacrol, the main component of this oil [41]. Thymol, one of the major compounds of thyme essential oil, has anti-inflammatory activity [21]. Thus, it seems that major components of these oils can complement one another, having synergic effects on inflammation so that their combination could exhibit positive preventive or therapeutic effects. A similar phenomenon was found in another study where the effect of peppermint oil and caraway oil on postinflammatory visceral hyperalgesia was examined (using a rat model of TNBS-induced colitis). Neither peppermint nor caraway oil administered individually had a significant effect on postinflammatory visceral hyperalgesia, but combined treatment with these essential oils significantly reduced the visceromotor response [42].