Modern screening techniques for plant extracts.

In order to discover new bioactive compounds from plant sources which could become new leads or new drugs, extracts should be simultaneously evaluated by chemical screening and by various biological or pharmacological targets. Chemical screening using hyphenated techniques such as LC/UV and LC/MS, and more recently LC/NMR, quickly provides ample structural information, leading in many cases to the identification of compounds. This allows researchers to distinguish between known compounds (dereplication) and new molecules directly from crude plant extracts. Thus, the tedious isolation of known compounds can be avoided, and a targeted isolation of constituents presenting novel or unusual spectroscopic features can be undertaken. In parallel, extracts are also subjected to various bioassays that should be simple, reproducible, and rapid. This approach will be illustrated by the search for new molluscicidal, antioxidant, and antifungal compounds from tropical plants.