Simultaneous Determination of Three Flavonoids in Rat Plasma by RP-LC After Oral Administration of the Total Flavonoids of Scutellaria barbata

A liquid chromatographic method for the simultaneous determination of three flavonoids, scutellarin (SCU), isoscutellarein-8-O-glucuronide (ISO) and luteolin (LUT) in rat plasma was developed and validated. Following a single-step liquid-liquid extraction with ethyl acetate, the analytes and internal standard (IS) (rutin) were successfully separated on a Diamonsil C-18 column using a mobile phase composed of acetonitrile (A)-0.2% phosphoric acid aqueous solution (B) (0-5 min, 20% A-29% A; 5-25 min, 29% A, v/v) at a flow rate of 1.0 mL min(-1). The linear range was 0.044-2.20 mu g mL(-1) for SCU, 0.042-2.08 mu g mL(-1) for ISO, and 0.056-2.80 mu g mL(-1) for LUT, with the correlation coefficients of 0.9995, 0.9989 and 0.9963, respectively. The limit of quantification of SCU, ISO and LUT were 44, 41.6 and 56 ng mL(-1), respectively. The accuracy of assay was between 88.4 and 103.0%. The inter-day and intra-day precisions (RSD) were less than 10.5%. The developed method was simple, rapid and applied successfully to study the pharmacokinetics of SCU, ISO and LUT after oral administration of the total flavonoids of Scutellaria barbata.