Phellamurin is a flavanone glycoside that is abundant in the leaves of Phellodendron wilsonii Hayata et Kanehira (Rutaceae). The disposition kinetics of phellamurin metabolites in rat brain was investigated in this study. Doses of 100 mg/kg and 200 mg/kg were orally administered to rats. At 0.33, 2, 4 and 6 hr after dosing, rats were dissected and the [)rain concentrations of the aglycone neophellamuretin were determined by an HPLC method prior to and after hydrolysis with [beta -glucuronidase. The mobile phase was acetonitrile: H2O (containing 1% acetic acid, 38:62, v/v). Our results indicated that neophellamuretin glucuronide might be able to cross the blood-brain barrier and its concentration in the brain was dose-dependent at the two doses investigated, whereas the aglycone neophellamuretin was present in a trace amount in the brain.