Biol. Pharm. Bull. 28(7) 1224—1228 (2005)

Ohwi (Leguminosae), has been clinically used as an antipyretic and spasmolytic agent in traditional Chinese medicine. Many Chinese herbal formulas contain Pueraria root as their major ingredient; most well-known being “Kakkon-To” (in Japanese), which is indicated for fever and chills with stiffness or rigidity of the neck and upper back. The constituents of Pueraria root have been studied extensively with various isoflavonoids, such as puerarin, daidzin, daidzein, genistin, and genistein, having been identified. The isoflavone O-glycoside daidzin inhibits cyclic AMP phosphodiesterase and induces differentiation in murine erythroleukemia cells. The C-glycoside puerarin exhibits hypoglycemic activity and increases coronary artery blood flow. The spasmolytic activity of daidzein, the aglycone of daidzin, has been demonstrated by a Magnus experiment using excised murine small intestine. On the other hand, genistein had estrogenic activity, a tyrosine kinase inhibitory action, and a histidine kinase inhibitory action. However, the active compounds in Pueraria root that produce antipyretic activity have not been identified. We previously showed that orally administered glycoside daidzin and genistin were hydrolyzed to the aglycone daidzein and genistein in vivo, respectively. Furthermore, daidzin or genistein were metabolized to dihydrodaidzein, equol or dihydrogenistein, p-ethylphenol through hydrogenation, reduction or ring-fission in vivo, respectively. Therefore, we investigated the pharmacological relationship between the antipyretic, analgesic, and muscle relaxant activities and chemical components of Pueraria root to identify the active compounds and to elucidate the empirical use.