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Abstract

A simple and sensitive high-performance liquid chromatographic (HPLC) method involving UV detection was developed for the determination of 9,10- anthraquinone-2-carboxylic acid (AQCA) in rabbit serum. A reverse-phase column (Lichrosher ®100RP-18) was eluted with a mobile phase of 0.4% phosphoric acid: acetonitrile (7:3) / methanol = 45 : 55 at a flow rate of 1.2 mL/min. The UV absorbance was monitored at 256 nm. After a simple clean- up procedure, the limit of quantitation achieved was 0.6 μg/mL and the standard curve was found to be linear over the serum concentration of 0.6 - 18μg/mL. The intra-assay and inter-assay coefficient of variance in serum was less than 2%, and the recovery was 96.98%. The established HPLC method was applied to the study of pharmacokinetics and bioavailability of 9,10- anthraquinone-2-carboxylic acid (AQCA). Eighteen healthy rabbits were divided into three groups and given intravenous (i.v.), oral and rectal administrations of different AQCA preparations with a single dose of 10 mg/kg. Blood samples were collected and AQCA concentrations in serum were analyzed. The results were performed with Winnolin programs and the ANOVA test (α = 0.05) was used to compare the pharmacokinetic parameters of AQCA in the three regimens. For the i.v. route, the t( 1/2 ) and AUC were 4.43 ± 0.13 hrs and 141.79 ± 7.84 μg*hr/mL, respectively. Parameters for the oral route were: T(max) = 7.17 ± 0.41 hrs; t( 1/2 ) = 15.32 ± 1.86 hrs; MRT = 20.02 ± 2.07 hrs and AUC = 107.53 ± 4.50 μg*hr/mL. The oral route indicated a slower absorption rate, a longer residence time and a lower extent of the AQCA absorption. For the rectal route, T(max) occurred at 1.58 ± 0.20 hrs, the t( 1/2 ) was 5.67 ± 0.82 hrs and the AUC was 121.18 ± 6.19 μg*hr/mL. The results indicated that the rate and extent of AQCA rectal absorption were better compared to those of the oral route. At this dose, the absolute bioavailabilities of AQCA were 0.876 and 0.872 for oral and rectal administrations, respectively. The differences of these pharmacokinetic parameters might be due to the physicochemical properties of AQCA in different conditions.

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