Overview of the Pharmacological Features of Honokiol

This paper provides an overview of the pharmacological features of honokiol (3′,5-di-2-propenyl-1,1′-biphenyl-2,4′-diol), an isomer of neolignans isolated and identified from the stem bark of Magnoliaceous plants (Magnolia obovata Thunb, Wa-Koboku in Japanese). The magnolia bark has been utilized as a herbal remedy for the treatment of a wide variety of clinical disorders. Honokiol and magnolol (an isomer of honokiol) were recently identified as anxiolytic agents in the extracts of Saiboku-to, an oriental herbal medicine (Kampo). Behavioral evaluation through an elevated plus-maze test demonstrated that honokiol, 0.2–2 mg/kg, p.o., for 7 days, was at least 5000 times more potent than Saiboku-to. Honokiol has a comparatively lower risk of causing benzodiazepine-like side effects, such as central depression, muscle relaxation, amnesia, or physical dependence. In addition to these central actions, a wide variety of pharmacological effects and biochemical activities of honokiol have been reported during the past 10 years. The main effects, including the limited information regarding the metabolism and kinetics of the compound, are briefly introduced in this text. Information available on honokiol, including its specific and simple chemical structure, suggests the possibility of deriving more potent compounds in the drug design process.