Anxiolytic Effect of Echium amoenum L. in Mice

Abstract

Putative activity of hydroalcoholic and aqueous infusion extracts of Echium amoenum L. was investigated in mice using the rotarod model of motor coordination and the elevated plus maze model of anxiety. The extracts were administered intraperitonealy (i.p.) once, one hour before performing the tests. Preliminary phytochemical study of the plant, with standard procedures, showed that it contains saponins, flavonoids, unsaturated terpenoids and sterols. There was no evidence of tanins, alkaloids and cyanogenic glycosides. The hydroalcoholic extract of Echium amoenum in the dose range employed (125, 250 and 500 mg/kg) had no significant effect on motor coordination while the aqueous extract (62.5, 125, 250 and 500 mg/kg) disrupted motor coordination significantly. Intraperitoneal injection of aqueous extract (5, 10, 20, 30, 62.5, 80 and 125 mg/kg) showed a significant dose-dependent increase in time spent in open arm (OAT) with no significant change in open arm entries (OAE), closed arm entries (CAE) and total arm entries (TAE). The anxiolytic effect was most evident in 125 mg/kg group. It is almost evident that the extract produces its anxiolytic effect in the doses in which no change in motor activity is observable. Comparison of the dose response curve with the anxiolytic dose response of diazepam (0.25, 0.5, 1.0 and 2.0 mg/kg) in the same setting showed that the maximal efficacy of the extract is significantly lower than diazepam. Because of different maximal efficacies we were not able to calculate Extract/diazepam potency ratio but it does not seem to be more than 1/100. It is concluded that single administration of aqueous extract of Echium amoenum L. produces a significant but mild to moderate anxiolytic effect.