Determination of 3-n-butylphthalide in rabbit plasma by HPLC with fluorescence detection and its application in pharmacokinetic study

A rapid, sensitive and specific reversed-phase high-performance liquid chromatographic method was developed for the determination of 3-n-butylphthalide, a drug currently being developed for treatment of stroke, in rabbit plasma. Fluorescence detection at an excitation wavelength of 280 nm and an emission wavelength of 304 nm was used for quantification of 3-n-butylphthalide. Ibuprofen was used as internal standard. Plasma samples were extracted with diethyl ether under acidic conditions. After evaporation of the organic phase, the extract was dissolved in mobile phase and injected into the chromatograph with C(18) column and a mobile phase of 0.05 mol/L sodium acetate buffer (pH 4.5)-acetonitrile (400:600). The peak area ratio vs concentration in plasma was linear over the range of 0.0212-4.24 microg/mL (correlation coefficient r = 0.9984) and the limit of quantification was 0.0212 microg/mL. Mean recovery was determined as 101.0% by analysis of plasma standard samples containing 0.0424, 0.424, 2.12 and 4.24 microg/mL of 3-n-butylphthalide. The intra-day relative standard deviations (RSDs) ranged from 3.6 to 8.9% and inter-day RSDs were within 8.0%. Pharmacokinetics of a single intravenous dose of 3-n-butylphthalide to the rabbits was presented to illustrate the applicability of this method. 3-n-Butylphthalide exhibited linear pharmacokinetics after intravenous administration to rabbits over the dose range 1-10 mg/kg.