The anxiolytic potential and psychotropic side effects of an echinacea preparation in laboratory animals and healthy volunteers

Abstract

We investigated the toxicity, psychotropic side effects and anxiolytic potential of an Echinacea angustifolia extract that produced promising effects in laboratory tests performed earlier. Rats were studied in the elevated plus-maze, conditioned fear, open-field, object recognition and conditioned place preference tests. Toxicity was studied in rats after intragastric administration. The preparation decreased anxiety in the elevated plus-maze and ameliorated contextual conditioned fear. No lethality or behavioural signs of discomfort were noticed in rats treated with 1000 and 3000 mg/kg Echinacea angustifolia. The extract was without effect in tests of locomotion (open-field), memory (object recognition) and rewarding potential (conditioned place preference) within a wide dose range. A pharmacological formulation based on the same E. angustifolia extract was tested in human subjects. One or two tablets per day were administered for 1 week to healthy volunteers scoring high on the State-Trait Anxiety Inventory (STAI). The tablets contained 20 mg of the plant extract. Data were collected using a structured self-assessment diary technique. The high dose (2 tablets per day) decreased STAI scores within 3 days in human subjects, an effect that remained stable for the duration of the treatment (7 days) and for the 2 weeks that followed treatment. The lower dose (1 tablet per day) did not affect anxiety significantly.