Ultrasound-assisted extraction coupled with SPE-HPLC-DAD for the determination of three bioactive phenylpropanoids from Radix Isatidis

Abstract

This study demonstrated a reversed-phase high performance liquid chromatography (RP-HPLC) with photo-diode array detection (DAD) method for simultaneous determination of three phenylpropanoids including syringin, clemastanin B and indigoticoside A in Radix Isatidis. Samples were extracted using ultrasound-assisted extraction (UAE). The optimal UAE conditions were: 80% (v/v) methanol solution, extraction time 45 min, a solvent to solid ratio of 20 mL g⁻¹, and temperature 60 °C. Under the optimized conditions, satisfactory extraction yields of the target analytes were obtained. The investigated analytes in extracting solution were concentrated in advance by solid phase extraction (SPE). Optimum conditions for SPE were achieved using 10 mL water as the washing solution and 5 mL water–methanol (50 : 50, v/v) for elution. Three analytes demonstrated good linearity (R² ≥ 0.9995) in a relatively wide concentration range. The method revealed high average recovery (range, 96.4–98.1%) and good precision with inter-day and intra-day variations of less than 0.69%. The validated method was successfully applied to quantify the three phenylpropanoids in eleven batches of Radix Isatidis obtained from different areas of China.