Evaluation of acute toxicity of a natural compound (+)-limonene epoxide and its anxiolytic-like action.

The aim of the study is to determine the acute toxicity and anxiolytic-like effects of a mixture of cis and trans of (+)-limonene epoxide in animal models of anxiety. After acute treatment with (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg (i.p.) no mortality was noted during 14 days of observation. In general, behavior, food and water consumption showed no significant changes. In open field test, (+)-limonene epoxide at doses of 25, 50 and 75 mg/kg, after intraperitoneal administration, significantly decreased the number of crossings, grooming and rearing (p<0.001). All these effects were reversed by the pre-treatment with flumazenil (25 mg/kg, i.p.), similar to those observed with diazepam used as a positive standard. In the elevated-plus-maze test, (+)-limonene epoxide increased the time of permanence and the number of entrances in the open arms. All these effects were reversed by flumazenil, an antagonist of benzodiazepine receptors. In addition, (+)-limonene epoxide (75 mg/kg) also produced a significant inhibition of the motor coordination (p<0.01), that was reversed by flumazenil. In conclusion, the present work evidenced sedative and anxiolytic-like effects of (+)-limonene epoxide, which might involve an action on benzodiazepine-type receptors. These results indicate that the properties of (+)-limonene epoxide should be more thoroughly examined in order to achieve newer tools for management and/or treatment of central nervous system diseases and anxiolytic-like effects. The LD50 obtained for the acute toxicity studies using intraperitoneal route of administration was 4.0 g/kg. These findings suggest that acute administration of the (+)-limonene epoxide exerts an anxiolytic-like effect on mice, and it could serve as a new approach for the treatment anxiety, since it practically does not produce toxic effects.