The Essential Oil of Myrtus communis L. Produces a Non-Sedating Anxiolytic Effect in Mice Models of Anxiety

Abstract

The myrtle shrub (Myrtus communis L., Myrtaceae) is rich in essential oils used in Ethiopian traditional medicine for the treatment of a variety of ailments, including anxiety. Anxiety is a common disorder that attacks many people in society and often accompanied by physiological sensations such as tachycardia, chest pain, shortness of breath, and insensitivity. The present study was undertaken to evaluate the anxiolytic effect of the essential oil of M. communis using different models of anxiety. Swiss Albino mice of either sex were randomly divided into six groups. Tween 80 (5%, v/v) in distilled water was administered to Group I and served as control. Group II was given diazepam (0.5 mg/kg, orally) suspended in Tween 80 and served as standard. Group III-VI were given the essential oil at doses of 50, 100, 200 and 400 mg/kg, respectively. Animals were then subjected to different anxiety tests, including elevated plus maze (EPM), stair case and open field. Parameters, among others, percentage of time spent in each arm and arm entries, number of steps climbed and number of rears, and number of crossings were then measured. Data were presented as mean ± SEM and analyzed by ANOVA followed by Tuckey posthoc test. In EPM studies, the essential oil at both 100 mg/kg (p<0.01) and 200 mg/kg (p<0.05), as well as diazepam (p<0.01) produced a significant increase in percentage of open arm time compared to controls. In the staircase setting, rearing was significantly decreased with 100 mg/kg (p<0.01) and 200 mg/kg (p<0.05) of the oil, and diazepam (p<0.05) relative to controls. However, at doses of 50 mg/kg and 400 mg/kg no detectable changes were noted on the measured parameters in both EPM and stair case models. The total number of entries into open field was comparable in all groups. At a dose of 100 mg/kg, the essential oil of M. communis showed better anxiolytic activity than the standard drug. The possible mechanism by which the oil showed the activity could be through GABA-related mechanisms. The present work, therefore, holds up the traditional use of the plant for the treatment of anxiety.

Keywords: Myrtus communis, essential oil, anxiety, elevated plus maze, stair case, open field