Chromatography: An important tool for drug discovery.

Despite substantial developments of extraction and separation techniques, isolation of natural products from natural sources is still a challenging task. Undoubtedly hybrid methods like liquid chromatography with NMR spectroscopy or liquid chromatography coupled with mass spectrometry made on-line structure elucidation possible and provided impressive examples of natural product identification without prior isolation, however, in many cases the necessity to get the purified compounds in hand is still a fact. The process begins with the collection of desired plant material which is subjected to the suitable extraction process. The complex crude extracts are then monitored by various chromatographic procedures to separate and quantify the desired compounds. The active plant extracts are then fractionated to isolate the bioactive compounds in their pure form. The fully identified compound is used as a lead for the production of related analogues to modulate the biological activity and to carry out structure-activity relationship. The major isolated bioactive compound is used for semi-synthetic modification or total synthesis should be carried out such that it is relatively easy to modify the structure of the lead compound. This is a simple and cost-effective way to increase the chance to discover lead compounds. The biological activity in vitro and in vivo has to be done after purification.