Ultrasonic-assisted micellar extraction and cloud-point pre-concentration of major saikosaponins in radix bupleuri using high performance liquid chromatography with evaporative light scattering detection

Abstract

A new ultrasonic-assisted micellar extraction and cloud-point pre-concentration method was developed for the determination of major saikosaponins, namely saikosaponins -A, -C and -D, in Radix Bupleuri by high performance liquid chromatography with evaporative light scattering detection (HPLC-ELSD). The non-ionic surfactant Genapol X-080 (oligoethylene glycol monoalkyl ether) was chosen as the extraction additive and parameters affecting the extraction efficiency were optimized. The highest yield was obtained with 10% (w/v) Genapol X-080, a liquid/solid ratio of 200:1 (mL/g) and ultrasonic-assisted extraction for 40 min. In addition, the optimum cloud-point pre-concentration was reached with 10% sodium sulfate and equilibration at 60 °C for 30 min. Separation was achieved on an Ascentis Express C18 column (100 × 4.6 mm i.d., 2.7 μm) using a binary mobile phase composed of 0.1% acetic acid and acetonitrile. Saikosaponins were detected by ELSD, which was operated at a 50 °C drift tube temperature and 3.0 bar nebulizer gas (N2) pressure. The water-based solvent modified with Genapol X-080 showed better extraction efficiency compared to that of the conventional solvent methanol. Recovery of saikosaponins ranged from 93.1 to 101.9%. An environmentally- friendly extraction method was successfully applied to extract and enrich major saikosaponins in Radix Bupleuri.