3.5. Determination of Bioactive Steroidal Saponins by HPLC

The concentrations of four steroidal saponins extracted by NADESs were determined using an Agilent 1260 HPLC system (Agilent, San Jose, CA, USA) equipped with a quaternary pump, an autosampler, a thermostatic column compartment and a diode array detector. Separation was performed on an Agilent ZORBAX Eclipse Plus C18 column (4.6 mm × 250 mm, 5 μm). The mobile phase consisted of water (A) and acetonitrile (B), and the gradient conditions were as follows: 0–5 min, 15% B; 5–30 min, 15–40% B; and 30–50 min, 40–50% B. The column temperature was set at 30 °C, and the flow rate was set at 1.0 mL/min. The detection wavelength was 203 nm, and the injection volume was 20 μL.