Baicalein,the aglycon of baicalin,is one of the main bioactive flavones in Scutellaria baicalensis Georsi.Five metabolites（M1-M5）and the parent drug（MO）were identified in rat serum after oral administration of baicalein at a dose of 200 mg/kg using the HPLC-DAD and LC-MS/MS methods.Based on the results,the possible metabolic pathway of baicalein in rat serum was proposed.
