Acute and Sub-chronic Oral Toxicity Evaluation of Eucalyptus globulusEssential Oil-Water Emulsion in Mice

Abstract

Background: plants are composed of bioactive chemicals some of which may be toxic. Therefore, scientists advocate for toxicological studies to be carried out in order to ensure the safety of drugs. Accordingly, this study was aimed to assess the possible toxic effects of Eucalyptus glubulus essential oil- water emulsion after oral administration in mice. Methods: The essential oil used in this study was obtained by extraction of the fresh leaves of E. glubulus through hydro-distillation technique. In the acute toxicity study, the mice placed in the seven treatment groups were administered with randomly selected 0.5 ml/kg initial dose up to 3.5 ml/kg body weight spaced by 0.5 ml/kg. The control animals received vehicle. All animals were gavaged the designated dose once and observed for the next two weeks. In the sub-chronic study, a control and two treatment groups, each containing twelve animals were used. Based on the findings of acute toxicity study, the two treatment groups were received 1.5 and 2.0 ml/kg body weight test doses respectively for three months in 24 hours interval. At the end study period, blood samples were taken by cardiac puncture and then, all animals were sacrificed and the vital organs were collected and processed for histopathological examination. Results: In the acute toxicity study, some toxicity signs and deaths of mice were recorded only at doses higher than 2.0 ml/kg body weight. 1 out of 6 mice in a group treated with 3.0 ml/kg and, 4 out of 6 animals in a group treated with 3.5 ml/kg body weight test doses of the emulsion were died following the administration. Therefore, the oral route LD50 of the emulsion falls between 3 ml/kg and 3.5 ml/kg. In the sub-chronic treatment, no death was recorded, and there was no statistically significant (p>0.05) change in the body weight, evaluated hematological and biochemical parameters of blood. However, minor pathological changes like; pyknosis and vacuolations of hepatocytes in some liver sections, and perivascular lymphocytic infiltrations and hyaline casts in renal tubules of some kidney sections, were observed in mice treated with 2.0 ml/kg body weight test dose. Conclusions and recommendations: The emulsion at relatively lower doses does not produce obvious toxic effects after acute and prolonged oral administration in mice. However, further investigation is needed to confirm this.