Simultaneous determination and pharmacokinetic studies on (3,4-Dihydroxyphenyl)-lactic acid and protocatechuic aldehyde in rat serum after oral administration of Radix Salviae miltiorrhizae extract

A simple and sensitive high-performance liquid chromatography method is developed for the simultaneous determination of (3,4-dihydroxyphenyl)-lactic acid (Dhpl) and protocatechuic aldehyde (Pal) in rat serum after oral administration of Radix Salviae miltiorrhizae extract. Serum samples are acidified with hydrochloric acid and extracted with ethyl acetate. Analysis of the extract is performed on a reversed-phase column and a mobile phase of 0.02% phosphoric acid-acetonitrile (91:9, v/v) with UV detection at 280 nm. Standard curves are linear in the range of 1.47-456.96 microg/mL for Dhpl and 0.124-7.936 microg/mL for Pal. For both regression coefficients, r(2) is greater than 0.993. Mean recovery is determined to be 75.23% and 84.06%, respectively, by analyzing serum standard containing 7.14, 57.12, and 228.48 microg/mL of Dhpl and 0.124, 0.992, and 3.968 microg/mL of Pal. The intraday precision (relative standard deviation) ranges from 3.91% to 12.03% at concentrations of 1.43, 57.12, and 228.48 microg/mL for Dhpl and 3.79% to 8.12% at concentrations of 0.124, 0.992, and 3.968 microg/mL for Pal. The interday precision (relative standard deviation) ranges from 5.06% to 9.93% for Dhpl and 3.05% to 10.00% for Pal, respectively, at the same three concentrations. This validated assay is applied to the determination of Dhpl and Pal concentrations and used to take a limited view of the pharmacokinetic profile in rat serum after oral administration of Radix Salviae miltiorrhizae extract.