A UHPLC–MS/MS method for simultaneous determination of six flavonoids, gallic acid and 5,8-dihydroxy-1,4-naphthoquinone in rat plasma and its application to a pharmacokinetic study of Cortex Juglandis Mandshuricae extract

• Developed a method for simultaneous determination of eight analytes in rat plasma.
• Study the pharmacokinetic of Cortex Juglandis Mandshuricae extract in rats.
• 5,8-Dihydroxy-1,4-naphthoquinone was determined first in rat plasma.
• Extraction with effective liquid–liquid extraction for all eight analytes.

Cortex Juglandis Mandshuricae is used as a folk remedy for treating cancer, diarrhea and dysentery in traditional Chinese medicine for many years. Six flavonoids (myricitrin, quercitrin, taxifolin, myricetin, quercetin and naringenin), gallic acid and 5,8-dihydroxy-1,4-naphthoquinone are major bioactive components in Cortex Juglandis Mandshuricae extract. In this study, an ultrahigh performance liquid chromatography and tandem mass spectrometry method was developed for simultaneous determination of eight ingredients in rat plasma using chloromycetin as an internal standard. Plasma samples added vitamin C (antioxygen) were acidified with hydrochloric acid and extracted by liquid–liquid extraction with ethyl acetate. Eight ingredients were separated on a Venusil ASB C18 column and detected by multiple reaction monitoring mode using electrospray ionization in the negative ion mode. The method was linear for all analytes over investigated range with all correlation coefficients greater than 0.9900. The validated lower limit of quantification was 20 ng/mL for gallic acid, 5 ng/mL for myricitrin, 3 ng/mL for quercitrin, 10 ng/mL for taxifolin, 6 ng/mL for myricetin, 3 ng/mL for quercetin, 2 ng/mL for naringenin and 1 μg/mL for 5,8-dihydroxy-1,4-naphthoquinone, respectively. Intra- and inter-day precisions (RSD%) were less than 15% and accuracy (RE%) ranged from −6.9% to 6.9%. The validated method was successfully applied to investigate the pharmacokinetics of the eight analytes after oral administration of Cortex Juglandis Mandshuricae extract to rats.