introduction to general methodology for screening of medicinal plants

ABSTRACT

Screening of plants is essential to explore the presence of novel compounds and to investigate their biological activities. Once the presence of such compounds is suspected, they are generally isolated in order to have material available for further biological and toxicological test[1, 2]. It is a cumbersome, tedious and lengthy process that starts from the selection of suitable plant/s to find out their pure constituents.It involves a continued effort that might last from weeks to years and includes the following steps: 1.Correct identification of the plant with the aid of specialists [botanists]. 2. Collection and drying of the vegetable material; precautions need to be taken to avoid the formation of artifacts. 3. Preparation of extracts using different solvents; analysis of these extracts by different chromatographic methods. 4.Fractionation of the extracts by different preparative chromatographic techniques [column chromatography, centrifugal partition chromatography etc.]. 5. Purity control of the isolated products. 6. Structure elucidation of the constituents by combination of diverse spectroscopic techniques [UV/VIS, IR spectrophotometry, carbon and proton nuclear magnetic resonance, mass spectrometry, X-ray diffraction] and chemical techniques [hydrolysis, formation of derivatives, degradation reactions etc.]. 7. Synthesis or semi-synthesis of the natural product. 8. Modification of structure with a view to establish structure-activity relationships. 9. Pharmacological and toxicological testing