Total content determination for the effective fraction of the alkaloids in Dicranostigma leptopodum (Maxim.) Fedde by HPLC and ultraviolet-visible spectrophotometry
For the quality control and the rational use of the effective fraction of the alkaloids (EFA) in Dicranostigma leptopodum (Maxim.) Fedde (DLF), extraction and determination methods for EFA were developed in the present study. The purification of EFA was carried out on the D101 macroporous resin. The high-performance liquid chromatography with the diode-array detection (HPLC-DAD) method was established to determine the total alkaloid content of EFA. In this method, 0.4% ionic liquid (1-butyl-3-methylimidazole tetrafluoroborate) was added into the mobile phase as the tailing-suppression reagent. 5-hydroxy-coptisine, isocorytuberine, protopine, allocryptopine, coptisine, berberine, corydine, and isocorydine were selected as reference standards for the determination, and the total alkaloid content was calculated as their sum in EFA. The results suggested that the total alkaloid content of EFA was 19.04 ± 1.23% (n = 3). Since corresponding reference standards for the alkaloids of DLF are lacking, ultraviolet-visible (UV-Vis) spectrophotometry was also developed for the determination of the total alkaloid content of EFA. In this method, isocorydine was selected as the reference compound for the determination of the total alkaloid content and the results suggested that the total alkaloid content of EFA was 65.92 ± 1.33% (n = 3). These newly established methods were rapid and accurate with high repeatability, and can be applied for the further use of EFA in DLF.