Biodiversity as a source of small molecules for pharmacological screening: libraries of plant extracts

Abstract

The term ‘biodiversity’ refers to the diversity of living organisms. This diversity of Life is represented as trees (called ‘taxonomic trees’) following the classification principles first proposed by Aristotle, then rigorously put forward by Linnaeus and connected to natural evolution by Darwin (in neo-Darwinian terms, trees are then called ‘phylogenic trees’). Beyond the unifying chemical features that characterise living entities (nucleotides, amino acids, sugars, simple lipids etc.), some important branches in the Tree of Life – like plants, marine invertebrates and algae, insects, fungi and bacteria etc. – are known to be sources of innumerable drugs and bioactive molecules. The exploration of this biodiversity was initiated in prehistoric times and is still considered a mine for the future. To allow access to libraries of extracts sampled in this biodiversity, a methodology has been designed following the model defined originally for single-compound chemical libraries. Thus ‘extract libraries’ have been developed to serve biological screening on various targets. There are far fewer extract-libraries than chemical libraries. The positive results obtained from these screenings do not straightforwardly allow the identification of a bioactive molecule, since extracts are mixtures of molecules, but they can orientate research projects towards the discovery of novel active compounds that can be potential drug leads.