The Anxiolytic Effect of Two Oriental Herbal Drugs in Japan Attributed to Honokiol from Magnolia Bark

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Abstract
An improved elevated plus-maze test in mice revealed that seven daily treatments with two differnt traditional Chinese medicines, known as Kampo medicines in Japan, Hange-koboku-to (composed of extracts of 5 plants) and Saiboku-to (composed of extracts of 10 plants), produced an anxiolytic effect, and the effect was mainly due to the presence of honokiol derived from magnolia. This study was carried out to evaluate the anxiolytic potential of honokiol, Hange-koboku-to and Saiboku-to, which were prescribed with two different magnolia samples: Kara-koboku (Magnoliae officinalis) (KA) or Wa-koboku (Magnoliae obovata) (WA). The doses of test samples were adjusted to ensure a constant dose of honokiol at 0.2 mg kg−1. Although the doses of magnolol (an isomer of honokiol), as well as those of undetermined chemicals, varied among samples, the seven daily treatments with 9 out of 10 test samples produced an anxiolytic effect almost equivalent to that produced by 0.2 mg kg−1 honokiol. The only exception was the sample containing the lowest amount of honokiol. Magnolia-free preparations of Hange-koboku-to or Saiboku-to did not have any anxiolytic effect. These results confirm that honokiol derived from magnolia is the causal chemical of the anxiolytic effect of Hange-koboku-to and Saiboku-to.