Comparison of Microwave‐Assisted and Ultrasound‐Assisted Extraction for Determination of Main Water‐Soluble Bioactive Constituents in Traditional Chinese Medicinal Preparation Tongmaichongji by HPLC‐DAD

Abstract

Microwave‐assisted extraction (MAE) and ultrasound‐assisted extraction (UAE) were compared as sample preparation methods for the determination of three main water‐soluble bioactive constituents (danshensu, puerarin, and ferulic acid) in traditional Chinese medicinal preparation (TCMP) Tongmaichongji by HPLC‐DAD. The optimal conditions of the two extraction methods were obtained. MAE could be completed in 2 min at 750 W of radiation power and 30% ethanol (pH 2.5) was used as extraction solvent. The time needed for UAE was 30 min, with 30% ethanol (pH 2.5) as extraction solvent. However, UAE allowed extraction at lower temperature. The present HPLC system used a Diamonsil C18 column (150 × 4.6 mm2, I.D. 5 µm) connected with Zorbax Ext‐C18 guard column (12.5 × 2.1 mm2, 4‐Pack) at 30°C, employing gradient elution with acetonitrile/water (pH 3) as mobile phase at a flow rate of 1 mL/min. The detection wavelength was set as: 0 min, 205 nm; 12 min, 254 nm; and 21 min, 320 nm. The linear calibration ranges were 6.8–81.9, 10.6–137.8, 4.9–77.8 µg/mL for danshensu, puerarin, and ferulic acid, respectively. The detection limits were 0.03, 0.10, 0.04 µg/mL for danshensu, puerarin, and ferulic acid, respectively. The contents of these three bioactive constituents in Tongmaichongji were successfully determined by the proposed method. The results indicated that there is a good agreement between the two extraction methods.