Determination of rhein in plasma, urine and feces by HPLC-fluorescence detection and its pharmacokinetics in healthy volunteers

This study established a HPLC-fluorescence detection (HPLC-FLD) assay for determining of rhein in human plasma, urine and feces on a reversed-phase C ₁₈ column with a mobile phase of methanol-acetonitrile-1% acetic acid (61:15:24). HPLC-FLD was performed at excitation wavelength 440 nm and emission wavelength 520 nm for rhein and the internal standard. Calibration curves were linear over the ranges of 0.05-10.00 μg/mL in plasma, 0.10-25.00 μg/mL in urine and 0.20-100.00 μg/mL in feces. The lowest limit of quantification for rhein was 0.05 μg/mL in plasma, 0.10 μg/mL in urine and 0.20 μg/mL in feces. The recovery of this method was greater than 80%. The main pharmacokinetic parameters c_max, t_max, AUC _0-∞, t_1/2 and MRT were (16.0 ± 3.4) μg/mL, (4.0 ± 0.6) h, (152.7 ± 45.7) μg·h/mL, (5.5 ± 1.1) h and (8.9 ± 2.2) h, respectively. The accumulative excretion rate of rhein in urine and feces were (8.19 ± 1.84) % and 11.00%, separately. This assay was proved to be convenient, accurate, sensitive and suitable for mass determination of biological samples.