Chemical investigation of plant constituents is strongly linked to the use of liquid chromatography (LC) at both the analytical and preparative level. Indeed, most of the secondary metabolites can be efficiently separated or isolated by different liquid chromatographic techniques. The plant extracts are generally screened by different bioassays and submitted to fractionation by chromatography. The fractions obtained are further tested for their biological activities. This process is repeated until the isolation of a pure active constituent, which is finally identified by spectroscopic methods (bioactivity guided isolation.