Since the dawn of time, humans have used plants to heal themselves. But it wasn’t until the 18th century that we began to understand that this healing power came from certain specific compounds: active ingredients. In a collective work for the general public entitled ’Plantes soignantes’ (Healing plants), the contributions of two biology researchers from the University of Neuchâtel, Emmanuel Defossez and Sergio Rasmann, retrace the major stages in this quest, the potential of which remains largely unexplored.
The idea behind our approach was to understand how it was possible to isolate and then identify the chemical composition of natural plant products of medical interest to humans", explains Sergio Rasmann, Professor of Biology and Director of the Functional Ecology Laboratory. In other words, how, over the course of civilizations, knowledge of the medical effects of plants passed from the realm of magic to that of alchemy, before modern science and its tools were able to provide answers at the molecular level.
We can cite three fundamental stages that led to the identification of substances responsible for medically interesting properties", notes Emmanuel Defossez, Senior Lecturer at the Functional Ecology Laboratory. During the Renaissance, although focused on minerals and rooted in a more mystical than scientific approach, the alchemical quest marked a first step towards the molecular description of living matter. The second milestone was reached by French chemist Antoine-Laurent de Lavoisier (1743-1794), whose work established the first links between the curative power of plants and the active principles they produce.
But it was the isolation of morphine, identified as a molecule, that marked the turning point towards modern scientific methodology. This feat was achieved by a group of Franco-German researchers, including Bernard Courtois (1777-1838) and Wilhelm Adam Sertürner (1783-1841).
The main difficulty, once a molecule had been isolated, was to prove its link with a therapeutic property. As the search for potential candidates was non-targeted, it was carried out at the rate of one compound after another, which rather limited the number of molecules to be characterized. It wasn’t until the 1970s and the widespread use of chromatographs combined with mass spectrometers that molecules could be identified in series.
The identification of molecules produced by an organism is now much faster, thanks to the increased sensitivity of mass spectrometry and computer processing power.
Today, we estimate that we know just 0.02% of the diversity of molecules with medicinal properties", says Emmanuel Defossez. Research is now counting on technological advances linked to machine learning to speed up the process of identifying new active plant ingredients, i.e. the 99.98% still to be discovered. The characterization of global chemical diversity is one of our research themes, with, in particular, the collaboration of Pierre-Marie Allard, from the University of Fribourg", adds Emmanuel Defossez.
Plantes soignantes / Entre pouvoirs et partages, edited by Blaise Mulhauser, PPUR, Epistémé collection, 264 pages, 2023. Also available in open access. www.epflpress.org
The plant origins of active ingredients