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Abstract
A sensitive, reproducible, simple, and accurate high performance liquid chromatographic (HPLC) method for the quantitative determination of quercetin in plasma has been developed and validated. Sample preparation involves simultaneous precipitation of plasma proteins and extraction of quercetin and kaempferol (the internal standard) from 0.1 mL plasma. The separation was performed in a stainless steel Ultrasphere-ODS column with a mobile phase consisted of a mixture of 30% acetonitrile and 70% of 5% acetic acid in HPLC water. The mobile phase was pumped at a flow rate of 1.5 mL/min and the effluent was monitored at 375 nm. The retention times for the drug and the internal standard were found to be 3.5 and 6.2 minutes, respectively. Peak-area ratios of the drug to the internal standard were used for quantitation of quercetin in plasma samples. The limit of detection of drug in plasma was found to be 0.06 μg/mL. The intra-day coefficient of variation (CV) ranged from 4.35% to 9.47%, and the inter-day CV ranged from 1.77% to 6.38% at three different concentrations.
Mean absolute recoveries ranged from 96.52% to 101.19% and the relative recoveries ranged from 92.64% to 111.03% at three different concentrations. Preliminary stability tests showed that quercetin is stable for at least 8 weeks in plasma after freezing at -20°C. The method was applied for the determination of the pharmacokinetic parameters of quercetin after intravenous administration to three rats.
ACKNOWLEDGMENT
The authors would like to express their appreciation for the valuable technical assistance of Mr. G. Mahrous.