Etude ethnobotanique de certaines plantes toxiques Employées dans la production des médicaments

Abstract

This document explores in depth the paradox according to which the toxicity and curative activity of plants are not opposed but inseparable, like two sides of the same pharmacological reality. Only dose and selectivity can transform a deadly poison into an essential medicine. The work, divided into two complementary parts, first establishes a scientific, toxicological, and regulatory theoretical framework, then illustrates it through monographs of emblematic plants and a survey of a specialized audience. Plant toxicity is neither fixed nor intrinsic: it results from complex interactions between factors specific to the plant (genetic variability, developmental stage, distribution of toxins), environmental factors (soil, climatic stress, season), preparation factors (heat treatment, route of exposure, solvent), and host factors (age, weight, genetics, physiological state). The work then classifies the main families of toxic substances (alkaloids, heterosides, terpenes,…) detailing their molecular mechanisms of action and clinical manifestations (cardiac, neurological, hepatic, etc.), showing how these molecules interfere with fundamental vital processes. The document traces the historical evolution from empirical ancient uses to modern biotechnologies, marked by the isolation of morphine (Sertürner, 1804), digitalin (Nativelle, 1844), curare in anesthesia, or the anticancer properties of the Madagascar periwinkle. Today, overly potent plant toxins are used as "warheads" in immunoconjugates (antibody-drug conjugates). Their therapeutic benefits cover oncology (vincristine, paclitaxel), cardiology (digitalis compounds), neurology (galantamine, curares), and rheumatology (colchicine), but this power comes with a narrow therapeutic index, severe adverse effects, and major standardization challenges. The second part presents the strict regulatory framework involving the WHO, pharmacopoeias, the EMA, ANSM, and the CITES convention. Quality standards rest on three pillars: botanical authentication, standardization by assay, and purity control (heavy metals, pesticides, microbial contaminants). Modern analytical methods (HPLC, GC-MS, atomic absorption spectrophotometry, NMR) ensure safety, complemented by preclinical toxicity assessment and active pharmacovigilance after marketing. Eight plants concretely illustrate these concepts: Purple Foxglove (heart failure via Na+/K+-ATPase inhibition), Belladonna (tropane alkaloids, antimuscarinic), Yew (paclitaxel and docetaxel anticancer agents), Opium Poppy (opioid analgesics, dependence risks), Castor Bean (extreme duality between toxic ricin and laxative or antifungal oil), Stinging Nettle (diuretic, anti-inflammatory, active in benign prostatic hyperplasia), Oleander (cardenolides studied for anticancer properties), and Bitter Apple (cytotoxic and antidiabetic cucurbitacins with a very narrow safety margin). A questionnaire administered to 37 respondents (mostly young, highly educated women) reveals near-unanimous consensus (97.3%) on the potential use of toxic plants as medicines, with dose recognized as the main toxicity factor by 81.1% of respondents. However, nearly 40% are unaware of the concept of "therapeutic margin," and the safety assessment of derived drugs remains divided (51.3% consider them safe). The demand is unanimous (100%) for more training of health professionals and for strengthened research. In the endv this work not only confirms the irreplaceable role of toxic plants as a source of medicines but also the urgent need to continue efforts in regulation, education, and research. Navigating between the formidable power of these substances and their precious curative potential requires a rigorous, systemic, and constantly vigilant approach.