isolation of plant compounds - methods of plant compound isolation (Jan/24/2006 )

what are the ways ppl normally isolate plant compounds?
what i know here is to do obtain the crude extract, followed by solvent-solvent partitioning. chromatography can then be used. What actually influenced the choice of methods or solvents used?

I guess one of the first issues would be the cost and availability of the solvents to be used. This also would go hand in hand with the solubility of the desired compound compared to any interferants in your crude extract. Finding a good solvent mixture is difficult. If there is any literature on previous extractions you may have to track those down.

well, i had so far proceeded till solvent-solvent partitioning and will be doing chromatography after this. i wonder what will be the appropriate sequence: column chromatography (silica gel as the stationary phase) followed by thin layer chromatography, or the other way round?