Determination of quinolizidine alkaloids in traditional Chinese herbal drugs by nonaqueous capillary electrophoresis

A rapid method for the determination of quinolizidine alkaloids by nonaqueous capillary electrophoresis was developed. A total of 10 alkaloids (matrine, sophocarpine, oxymatrine, oxysophocarpine, sophoridine, cytisine, sophoramine, aloperine, lehmannine and dauricine) could be easily separated within 18 min. A running buffer composed of 50 m M ammonium acetate, 10% tetrahydrofuran and 0.5% acetic acid in methanol was found to be the most suitable for this separation. Five of these alkaloids were selected for further studies. The linear calibration ranges were 2.51–50.1 μg/ml for sophoridine and sophocarpine, 2.71–54.2 μg/ml for matrine, 3.30–65.9 μg/ml for oxymatrine, and 3.10–62.0 μg/ml for oxysophocarpine. The recovery of the five alkaloids was 98.0–101.3% with relative standard deviations from 1.03 to 2.68% ( n=5). The limits of detection for all 10 alkaloids were over the range 0.93–2.31 μg/ml. The method was successfully applied to the phytochemical analysis of alkaloid extracts from three commonly used traditional Chinese herbal drugs: Sophora flavescens Ait. (Kushen), S. alopecuroides L. (Kudouzi or Kugancao) and S. tonkinensis Gapnep (Shandougen).