A study of the behaviour of some new column materials in the chromatographic analysis ofCatharanthus alkaloids

Optimisation of supercritical fluid extraction of indole alkaloids from Catharanthus roseus using experimental design methodology--comparison with other extraction techniques

Response surface modelling, using MODDE 6 software for Design of Experiments and Optimisation, was applied to optimise supercritical fluid extraction (SFE) conditions for the extraction of indole alkaloids from the dried leaves of Catharanthus roseus. The effects of pressure (200-400 bar), temperature (40-80 degrees C), modifier concentration (2.2-6.6 vol%) and dynamic extraction time (20-60 min) on the yield of alkaloids were evaluated. The extracts were analysed by high-performance liquid chromatography and the analytes were identified using ion trap-electrospray ionisation-mass spectrometry. The method was linear for alkaloid concentration in the range 0.18-31 microg/mL. The limits of detection and quantification for catharanthine, vindoline, vinblastine and vincristine were 0.2, 0.15, 0.1 and 0.08 microg/mL and 2.7, 2.0, 1.3 and 1.1 microg/g, respectively. The dry weight content of major alkaloids in the plants were compared using different extraction methods, i.e. SFE, Soxhlet extraction, solid-liquid extraction with sonication and hot water extraction at various temperatures. The extraction techniques were also compared in terms of reproducibility, selectivity and analyte recoveries. Relative standard deviations for the major alkaloids varied from 4.1 to 17.5% in different extraction methods. The best recoveries (100%) for catharanthine were obtained by SFE at 250 bar and 80 degrees C using 6.6 vol% methanol as modifier for 40 min, for vindoline by Soxhlet extraction using dichloromethane in a reflux for 16 h, and for 3',4'-anhydrovinblastine by solid-liquid extraction using a solution of 0.5 m sulphuric acid and methanol (3:1 v/v) in an ultrasonic bath for 3 h.

Symmetry C18 column: a better choice for the analysis of indole alkaloids of Catharanthus roseus

By virtue of the different elution patterns of vindoline, catharanthine, vincristine and vinblastine present in the leaves of Catharanthus roseus plants, a Symmetry C18 column provided a better resolution for all of these compounds as compared with other C18 columns. The binary gradient system with a linear gradient profile, employed in a method developed using a Symmetry C18 column, gave excellent peak symmetry, resolution and reproducibility. Detection was performed at 220 nm which presented better absorptivity for these indole alkaloids giving a minimum detection limit of 0.5 microgram. Photodiode array detection was used to determine the homogeneity and purity of each compound. The described analysis is rapid and economical to perform as small amounts of solvent are consumed per analysis, and the method will find application where a large number of samples are to be analysed as, for example, in crop improvement studies where plants need to be selected regularly on the basis of alkaloid production.