Simultaneous determination of four flavonoids and one phenolic acid in rat plasma by LC–MS/MS and its application to a pharmacokinetic study after oral administration of the Herba Desmodii Styracifolii extract

A sensitive and selective liquid chromatography and tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of four flavonoids (schaftoside, isovitexin, luteolin, and apigenin) and one phenolic acid (ferulic acid) in rat plasma using sulfamethoxazole as the internal standard (IS). The separation was performed using a Diamonsil C18 column, which was eluted with methanol (A) and 0.1‰ acetic acid (B). The gradient condition was as follows: 0–5 min, 40–60% A; 5–6 min, 60–95% A; and 6–10 min, maintained at 95% A. The analytes were detected using a hybrid quadrupole linear ion trap mass spectrometer that was equipped with an electrospray ionization source in the negative ion and multiple-reaction monitoring modes. A full validation of the method was performed. The linearity of the analytical response was good, with correlation coefficients greater than 0.9925 for all of the compounds within the concentration range. The lower limits of quantitation (LLOQ) of schaftoside, isovitexin, luteolin, apigenin, and ferulic acid in rat plasma were 1.66, 0.84, 3.69, 1.70, and 3.91 ng/mL, respectively. The intra-day and inter-day precisions of the investigated components exhibited an RSD within 13.20%, and the accuracy (RE%) ranged from −8.47% to 10.90%. The results indicated that the developed method is sufficiently reliable for the pharmacokinetic study of schaftoside, isovitexin, apigenin, luteolin, and ferulic acid in rats following oral administration of the Herba Desmodii Styracifolii extract.