A simple method for separating sanguinarine and chelerythrine based on preparative acid-base titration

Abstract

Introduction. The benzophenanthridine alkaloids sanguinarine (SA) and chelerythrine (CHE) exhibit antimicrobial, anti-inflammatory, anticancer, and other properties. While structurally similar, they differ in the strength of their pharmacological effects and in their mechanisms of action, although they are present together in plants. Therefore, the task of their preparative separation is of current practical inportance. Materials and methods. A mixture of SA and CHE bisulfates, obtained from Macleaya microcarpa leaves, was separated into individual alkaloids using the method developed in this work, based on titration with di- and trisubstituted phosphates. The resulting alkaloid pseudo-bases were converted back to bisulfates for further study or additional fractionation. Analysis of the raw materials, intermediates, and final products was performed using high-performance liquid chromatography (HPLC) and ultraviolet spectrophotometry. Results. By fractionating 2.5 g of the bisulfate mixture containing 39.2% SA and 33.7% CHE by weight, 899 ± 36 mg of the SA fraction with an SA content of 90.6 ± 1.1% by weight or 95.4 ± 1.2% of the total alkaloids and a recovery of 83.1 ± 4.7%, 463 ± 19 mg of the CHE fraction with a CHE content of 93.4 ± 0.2% by weight or 98.1 ± 0.2% of the total alkaloids and a recovery of 51.3 ± 4.2%, and 344 ± 26 mg of the intermediate fraction containing 19.1 ± 2.8% SA and 76.1 ± 2.8% CHE by weight were obtained (N = 5). Repeated fractionation increased the purity of SA and CHE fractions, and processing of the intermediate fraction allowed an additional amount of CHE to be obtained. Conclusions. A simple method for separating a mixture of SA and CHE into individual alkaloids, based on their sequential precipitation as pseudo-bases during acid-base titration, was developed. This method provides good separation of the alkaloids without the use of expensive technologies.