Rapid quantitative analysis of six flavonoids in licorice by ultra-performance convergence chromatography

Abstract

Objective: This study was to establish a rapid quantitative method for determination of six characteristic flavonoids, including licochalcone A (1), liquiritigenin (2), glabridin (3), isoliquiritigenin (4), liquiritoside (5), and isoliquiritoside (6) in licorice by a ultra-performance convergence chromatography (UPC2) apparatus equipped with a photodiode-array detector (PDA). Methods: The flavonoids studied were separated on an ACQUITY UPC2 TM Torus 2-PIC column (2.1 × 100 mm, 1.7 μm) using gradient elution (85:15–70:30) with a mobile phase consisting of CO2 and methanol: formic acid (99.8:0.2, v/v), back pressure of 2,000 psi, flow rate of 0.8 mL/min, and detection at 254 nm. This method was further applied for the analysis of the flavonoids present in 10 batches of licorice roots samples. Results: Good linearity (R2 = 0.9990–0.9998) was achieved and limits of detection (LOD) and quantification (LOQ) ranging from 0.12 to 0.49 µg/mL and 0.46 to 1.61 µg/mL, respectively. The relative standard deviations (RSD) for repeatability and reproducibility were 2.30–2.80% and 2.30–2.98%, respectively. The flavonoids distributed differently in Glycyrrhiza uralensis, Glycyrrhiza glabra, and Glycyrrhiza inflate. Conclusion: The established rapid quantitative analysis method was environment friendly and suitable to the quality control of species licorice.