A sensitive RP-HPLC-UV method has been developed and validated for the quantification of daphnoretin in rat plasma. Daphnoretin was extracted from rat plasma by protein precipitation and liquid-liquid extraction. Separation was performed on a Diamonsil C18 column （200 mm× 4.6 mm, 5 μm） with a mobile phase of methanol-20 mmol/L ammonium acetate （adjusted to pH 3.2 with acetic acid, 42：58, v/v） at a flow rate of 1.0 mL/min. The UV detector was set at 345 nm and column temperature was set at 40 ℃. The calibration curves were linear over the concentration range of 0.020-2.00 ~tg/mL, The lower limit of quantification （LLOQ） of daphnoretin in rat plasma was 0.020 μg/mL. The intra- and inter-day relative standard deviation （RSD） for measurement of quality control （QC） samples （0.050, 0.200 and 1.60 μg/mL） ranged from 5.0%-10.6%. Relative error （RE） was from ±（1.2%-2.5%）. The validated method was used successfully in a pharmacokinetic study of daphnoretin in rats after intraperitoneal injection.
