Natural products are organic compounds, which are isolated from natural sources such as plants, microorganisms, marine organisms and animals. These organisms rely mainly on their chemical defense by producing the organic compounds also termed as secondary metabolites. Natural products are a rich source of new pharmaceutical agents. Recent survey indicates that ca.60% of anti-cancer and anti-infective agents that commercially available or in the late stages of clinical trials are of natural products origin. My primary research interest is isolation of new pharmaceutical agents from natural sources, chemical transformations of bioactive natural products, design of activity-guided screening of natural product extracts for medicinal research. Chemotaxonomic studies, chemical fingerprinting of essential oils isolated from various aromatic plants with the help of GC and GC-MS. Various modern chromatographic techniques such as High Performance Liquid Chromatography (HPLC), High Performance Thin Layer Chromatography (HPTLC), Centrifugally Accelerated Radial Thin Layer Chromatography (Chromatotron), Flash Chromatography, Vacuum Liquid Chromatography (VLC), Flash chromatography, Column Chromatography (CC) and Preparative Thin Layer Chromatography (pTLC) are used for the isolation and purification of highly complex polar and non-polar mixtures of bioactive natural products. Structure of the pure secondary metabolites and their modified analogues are established with the help of extensive spectroscopic studies such as one-dimensional (1H-NMR, 13C-NMR and DEPT), two-dimensional (COSY, NOESY, TOCSY, HMQC and HMBC) NMR experiments, HPLC, mass spectrometry (EI, CI, FAB, LC-MS, GC-MS and linked scan), UV and IR spectrophotometers.