Determination of quercetin in dietary supplements by isocratic RP-HPLC method

Abstract

Quercetin is a natural flavonoid found abundantly in vegetables and fruits. It shows antioxidant, anti-inflammatory, antihepatotoxic, antiallergic, antidiabetic and antiviral activity. Increasingly popular dietary supplements containing quercetin require critical examination of their quality. The aim of this study was to develop a simple and accurate HPLC method for quercetin determination in dietary supplements. Chromatographic separation was achieved by isocratic method, using a Purospher STAR® RP-18 reverse-phase column (150 x 4.6 mm i.d., particle size 5 μm), a mobile phase composed of acetonitrile and water (acidified to pH 3.0), in a ratio of 30:70 (V/V), run at a flow rate of 1.1 mL/min. The column temperature was kept at 30 °C. The DAD detector was set at 257 nm and 375 nm. The injection volume was 20 μL. Isopropanol was used as a solvent. The method was validated by determining system suitability, specificity, linearity, range, limit of detection and quantification, accuracy, precision, and robustness. It is characterized by simple preparation, good precision (RSD ˂ 2%) and good analytical yield (100.09% and 100.29% at 257 nm and 375 nm, respectively). The limit of detection and quantification were 0.00071 μg/mL and 0.00215 μg/mL at 257 nm, and 0.00078 μg/mL and 0.00236 μg/mL at 375 nm, respectively. The system suitability test showed that method performance is similar at both wavelengths. This method can be recommended for routine analysis of dietary supplements containing quercetin in food quality control laboratories. Keywords: quercetin, HPLC, dietary supplements, flavonoid