A capillary zone electrophoresis method for the assay and quality control of mesembrine in Sceletium tablets

The Sceletium plant has been reported to contain psychoactive alkaloids, specifically mesembrine, mesembrenone, mesembrenol and other related alkaloids. Sceletium is marketed through health shops and on the internet as dried plant powder and as pharmaceutical dosage forms. The objectives of this research was to develop and validate a capillary zone electrophoresis (CZE) method to identify five alkaloids and quantitatively determine the content of the important alkaloid, mesembrine in Sceletium tablets. Since reference standards of the relevant alkaloids are not commercially available for use in quality control of Sceletium products, it was necessary to isolate and characterize an appropriate analytical marker for use in the assay and additional markers for fingerprinting by CZE. The separation of the relevant alkaloids was carried out by CZE on a 50 cm effective length, fused silica capillary tubing (50 mu m i.d. x 360 mu m o.d.) using 50 mM of sodium dihydrogen orthophosphate dihydrate at pH 1.5 as the background electrolyte and monitored at a UV wavelength of 228 nm. All the marker alkaloids were found to be well resolved and were identified in the plant material and in commercially available Sceletium tablets based on the relative migration times (MTs) with respect to quinine hydrochloride that was used as an internal standard. The method was validated and used to assay the mesembrine content in Sceletium tablets. Calibration curves were found to be linear over the entire concentration range of 2.5-80 mu g/ml with correlation coefficients > 0.995. The accuracy was found to be 92.5 and 104.5% (R.S.D. < 3.5%) and the R.S.D.'s of the inter-day precision at low, medium and high tablet masses were better than 0.9, 2.2 and 2.7%, respectively. The recoveries were all within the range of 91.8 and 105.8% (R.S.D. < 8.5%) and the limit of quantitation (LOQ) and limit of detection (LOD) values were found to be 2.5 and 1.5 mu g/ml, respectively. (c) 2008 Elsevier B.V. All rights reserved.