Determination of tamarixetin and kaempferide in rat plasma and urine by high-performance liquid chromatography

Tamarixetin and kaempferide, the major bioactive constituents of Xiheliu extract, have been simultaneously/quantitatively determined in rat plasma and urine by a sensitive high performance liquid chromatography method after oral administration the total flavonoids from Xiheliu. In this study, the biological samples were prepared by solid-phase extraction, then simultaneously detected at 254 nm and successfully separated and quantified using a reversed-phase [C.sub.18] column with methanol-formic acid aqueous gradient solution, at a flow rate of 1 mL/min. Good linearity (r > 0.989) of tamarixetin was observed in plasma and urine with the calibration ranges both at 1.6-80 µg/mL. For kaempferide, the correlation coefficient reached 0.994 in plasma at 1.4-70 µg/mL. The RSD of intra- and inter-day were 1.9-6.5% for tamarixetin and 1.3-9.0% for kaempferide in plasma; in urine, the intra- and inter-day RSD for not only tamarixetin but also kaempferide was no more than 7.4 and 5.8%, respectively. The lowest extraction recovery was 87.6% for kaempferide and 93.2% for tamarixetin in plasma and urine for both low and high concentrations. Due to the high sensitivity (the LOQ for tamarixetin was 1.2 µg/mL and for kaempferide 1.4 µg/mL), accuracy, precision, and good selectivity, the assay was successfully applied to pharmacokinetic studies of both flavonols in rats. The half-lives of tamarixetin and kaempferide were 17.8 ± 1.4 and 92.5 ± 1.6 min, and the [c.sub.max] were 3.1 ± 0.2 and 2.5 ± 0.4 µg/mL, respectively. Keywords: tamarixetin, kaempferide, liquid chromatography DOI: 10.1134/S106193481406015X
Tamarix chinensis L. (Chinese name Chengliu) was widely distributed on the beach of Jiangsu province, P. R. China. The twig of Chengliu named Xiheliu, used as a traditional Chinese medicine [...]