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Formation of alkaloid artifacts may contribute to explain Mondia whitei (Hook.f.) Skeels bioactivity

par Bunel, Valérian ;Hamel, Marie;Duez, Pierre ;Stévigny, Caroline
Référence International Symposium AFERP & STOLON (22-24/05/2013: Bruxelles, Belgique)
Publication Non publié, 2013

Poster de conférence

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Résumé :

Mondia whitei (Hook.f.) Skeels (Apocynaceae) is used across sub-Saharan Africa to treat a vast range of diseases and health conditions. The root is commonly chewed by men for its aphrodisiac and tonic properties, but it is also used for the treatment of asthenia and depression; these indications are suggestive for an effect at the central nervous system's level. Consistent with the botanical family of M. whitei, previous phytochemical analyses have revealed the presence of alkaloids whose structures still remain unknown. Along the isolation and characterization of M. whitei alkaloids, these were found to be resulting from the formation of an artifact issuing from the known aromatic compound 2-hydroxy-4-methoxybenzaldehyde (2H4MBZA). The classical extraction process of alkaloids, based on the acid/base equilibrium of this class of compounds, requires the use of alkalizing substances, such as ammonia. This base reacts with the aldehydic carbonyl of 2H4MBZA through a nucleophilic substitution reaction, yielding a new nitrogen compound. We next investigated 2H4MBZA's reactivity towards the neurotransmitters: epinephrine, norepinephrine, dopamine, serotonin and γ-aminobutyric acid (GABA). Except for epinephrine, these biogenic amines were able to react with 2H4MBZA, forming derived products whose putative structures were confirmed via mass spectrometry analysis.We suggest that the formation of such derivatives may explain the bioactivity of M. whitei in modulating the affinity of the neurotransmitters towards their receptors.