Separation strategies of plant constituents--current status.
The paper summarizes the state of art of different separation methods which are used for the analysis and isolation of plant constituents. An overview about the extraction methods which are frequently used for the non-volatile constituents of plants is given. Special attention is paid to the identification possibilities of non-volatile and volatile compounds, since generally the role of identification of plant's constituents is undervalued. We would emphasize the facts that, for correct identification, the various chromatographic and spectroscopic methods have to be used in conjunction. The application of two different methods from each field is usually sufficient. For quantitative information, two independent methods are necessary and are acceptable if the results are within 3% of each other. If only one method is available for quantitative analysis, the results can only be accepted if, using the global optimum, the ratios of the components determined are identical to one decimal place with the ratios of three measurements (local optima) using different mobile phases with different selectivities. Based on our own 20-year experience and more than a hundred isolated compounds, we give an isolation strategy where the structures and properties of the compounds to be isolated do not have to be known. It is pointed out that without analytical monitoring, the results of preparative separations cannot be guaranteed.