I have a query about isolation of effective compound from crude extract of plant. how can i possibly separate different fraction of pure compound from crude extract and how to characterized them for their purity.
The xantholides are a well characterised group of sesquiterpene lactones. A search of the literature will doubtless result in a number of descriptions of their isolation and purification. They can be extracted with a non polar solvent followed by column chromatography to yield an enriched fraction. From there you can move to a HPLC for a high resolution separation. If you have a bioassay of some sort then you can use this to guide the isolation process. You can test for purity using mass spectrometry, spectroscopy or NMR, possibly in conjunction with LC or GC (if they are thermally stable).
It is difficult to be much more specific given we don't know what equipment you have access to. If you can provide more detail on specific problems we would be better able to help. A good library search is the best way to start.