Rhodiola rosea is a medicinal plant used by the indigenous Inuit people of Nunavik and Nunatsiavut, Eastern Canada, as a mental and physical rejuvenating agent. This traditional use led to the present investigation of R. rosea in the context of anxiety disorders. An alcohol extract of R. rosea roots was characterized phytochemically and orally administered for three consecutive days to Sprague-Dawley rats at 8 mg/kg, 25 mg/kg, and 75 mg/kg body weight. The rats were subjected to three behavioral paradigms of anxiety, including the elevated plus maze, social interaction, and contextual conditioned emotional response tests. Rhodiola rosea showed dose-dependent anxiolytic activity in the elevated plus maze and conditioned emotional response tests, with moderate effects in the higher-anxiety SI test. The active dose varied according to the anxiety test. In order to elucidate a mechanism, the extract was further tested in an in vitro GABAA-benzodiazepine receptor-binding assay, where it demonstrated low activity. This study provides the first comparative assessment of the anxiolytic activity of Nunavik R. rosea in several behaviour models and suggests that anxiolytic effects may be primarily mediated via pathways other than the GABAA-benzodiazepine site of the GABAA receptor.
This is the first report on the phytochemistry of Nunavik (Québec, Canada) populations of Rhodiola rosea L., a medicinal plant widely used in Eurasia as a tonic and adaptogen. The wild harvested rhizome of the Nunavik populations contained the marker phytochemicals (salidroside, rosarin, rosavin and rosin) reported in authentic Eurasian material, although in lesser amount. Phytochemical profiling by HPLC of the Nunavik populations also showed the presence of new marker compounds not found in the Eurasian material. For quantitative analysis of the phytochemicals, method validation was undertaken, and the marker phytochemicals were measured in the rhizome, leaf, stem, and seeds. The rhizome showed the highest amount of salidroside and rosavins, as well as the highest total phytochemical content. Consequently, the rhizome remains the most medicinally valuable part of R. rosea.
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