Efficient Preparation of Hangekobokuto (Banxia-Houpo-Tang) Decoction by Adding Perilla Herb before Decoction is Finished

Hangekobokuto (banxia-houpo-tang) is a Kampo (traditional Japanese) medicine used mostly for anxiety disorder and consists of Pinellia Tuber, Poria Sclerotium, Magnolia Bark, Perilla Herb and Ginger. Perilla Herb contains an essential oil rich in perillaldehyde, which has a pleasant flavor, but this is easily lost due to heating. We therefore investigated how the major constituents of hangekobokuto, namely perillaldehyde, rosmarinic acid, magnolol and [6]-gingerol, varied with time during decoction and approached an optimal condition for decoction. Rosmarinic acid at 15 min after boiling, and magnolol and [6]-gingerol at 30 min were mostly extracted, while 0.09 mg of perillaldehyde remained at 15 min, but was not detected at 30 min. From these results, a decoction was prepared by adding Perilla Herb 1, 2, 5 and 10 min prior to the termination time of decoction at 30 min. When Perilla Herb was added 1 min beforehand, perillaldehyde was abundant (1.58 mg) and the amount of rosmarinic acid was already the same as that in the conventional decoction at 30 min, but the amount of total extract was inadequate. When Perilla Herb was added 5 min beforehand, perillaldehyde remained to some extent (0.61 mg) and rosmarinic acid was significantly increased compared with that in the conventional decoction at 30 min. From these results, we can conclude that the decoction should be prepared by boiling for not more than 30 min and, if possible, Perilla Herb should be added 5 min prior to the termination time. Considering the antidepressant-like activity of perillaldehyde and rosmarinic acid, the suggested method will not only achieve better treatment for anxiety, but also provide an effective use of crude drugs in the resource-limited environment.