QUANTIFICATION OF VINCRISTINE AND VINBLASTINE IN CATHARANTHUS-ROSEUS PLANTS BY CAPILLARY ZONE ELECTROPHORESIS

A systematic and comprehensive study of the separation and quantificat ion of two dimeric catharanthus alkaloids, vincristine (VC) and vinbla stine (VB), in Catharanthus leaves by capillary zone electrophoresis ( CZE) was conducted. Various separation parameters such as buffer conce ntration and pH, column internal diameter and applied voltage were stu died. Due to the complexity of the samples, the optimum conditions for separating VC and VB from other alkaloids that co-exist in the plant samples are matrix-dependent. We found the following conditions, in ge neral, gave the best results in terms of resolution and analysis time: column, 72 cm (57 cm effective length)X 75 mu m I.D.; buffer, 0.2 M a mmonium acetate solution, pH 6.2 and an applied voltage of 10 kV. Alth ough the separation of VB and VC was the primary focus, the separation parameters determined in this study can be applied to the separation of other alkaloids as well. Separation of many of the other alkaloids in the plant samples was observed under conditions presented in this p aper. A secondary objective of this study was to develop a method with experimental conditions which could be applied to electrophoresis-mas s spectrometry, For this reason, ammonium acetate buffers, which an mo re compatible with mass spectrometry than the widely used phosphate bu ffers, were used exclusively. Also, methanol-water-acetic acid was use d as external buffer for the same reason. The effects of this buffer a nd its compositions on the resolving power of CZE for the VB/VC pair a re discussed.