Anti-anxiety activity of Stachys tibetica Vatke

S. tibetica Vatke is a herb distributed in the tropical and subtropical regions of the world, including Tibet, China, and India. In India it is found in the cold desert regions of Kargil, Ladakh Valley, and in the mountains of Himachal Pradesh. The traditional practitioners in the Kargil and Ladakh use the natural medicine Stachys tibetica for the treatment of various mental disorders and phobias. The present study is aimed at evaluating the anxiolytic effects of the methanolic extract of the root, stem, leaf, and whole plant material of Stachys tibetica Vatke in rats.

Powdered materials (1 kg) of each plant part were subjected to extraction in a Soxhlet apparatus with methanol (95%); to yield 12.8%, 8.3%, 17.2%, and 19.6% W/W extractives, respectively. Extracts were evaluated for their anxiolytic effects using the elevated plus maze (EPM) test in rats.

In the present study, it was found that the methanolic extracts (200 and 400 mg·kg(-1)) of the root, stem, leaf and whole plant of Stachys tibetica Vatke and diazepam (DZ) increased the time spent and the number of entries in the open arm significantly (**P < 0.01), while they decreased the time spent and the number of entries in the closed arm. At the same time, all of the extracts and DZ decreased the time spent at the center of the maze (latency), along with closed arm returns. The head dip counts increased significantly in the rats treated with DZ, SMR400, SML400 and SMW400 in the open arm of EPM, which was a sign of reduction anxiety. The DZ and SMW did not show the fecal bolus, while other groups had reduced fecal bolus (**P < 0.01) as compared to control. These allied parameters helped to assess the anxiolytic potential of Stachys tibetica Vatke. Whole plant and leaf materials have shown the maximum activity, the root intermediate while the stem had the least anxiolytic activity (*P < 0.05, **P < 0.01) in EPM.

The results strongly justify the use of this plant for the treatment of anxiety. Further studies are in progress in this laboratory to isolate and identify the components responsible for the anxiolytic activity and the mechanism of action involved.