Métabolites secondaires des extraits des écorces du tronc et des racines d’Anonidium mannii Engl. & Diels (Annonaceae) : Évaluation de leurs activités antischistosomiases

Abstract

The present work relates to the chemical study and evaluation of the antischistosomal and inhibitory properties of enzymes of extracts and chemical constituents of a Cameroonian plant species: Anonidium mannii (Annonaceae). This plant is used in traditional medicine for the treatment of malaria, cancer, schistosomiasis and/or their symptoms. Their extracts (stem barks and roots) showed interesting antischistosomal and enzymatic activities in vitro during the preliminary screening on Schistosoma mansoni and on SmNACE. Phytochemical investigation, using the usual chromatographic methods, led to the isolation of eight compounds from the stem barks and nine other from the roots. At last, twelve compounds have been fully characterized using spectroscopic techniques (UV, IR, SM, 1D and 2D NMR) and by comparison of some physical and spectral data with those described in the literature. One of these compounds is isolated for the first time. It is an alkaloid: manniindole. The eleven other compounds, all known, belong to various classes of natural substances, among which: three alkaloids (aristolactams) (aristolactam AII, aristolactam BII, piperolactam D), a flavonoid (epicatechin), a phenolic acid (gallic acid), four pentacyclic triterpenes (polycarpol, α-amyrin, lupeol, lanosta-7,9-(11),23-triene-3β,15α-diol), two steroids (β-sitosterol and stigmasterol). Furthermore, the acetylation of the aristolactams AII and BII led to the production of two derivatives: aristolactam AII diacetylated, aristolactam BII acetylated, respectively. Among these two derivatives, acetylated aristolactam BII is obtained for the first time. Similarly, apart from polycarpol, lanosta-7,9(11),23-triene-3β,15α-diol, β-sitosterol and stigmasterol, all the other compounds, although known in the literature, were isolated for the first time of the genus Anonidium. The stem barks and roots extracts and some isolated compounds have been tested for their antischistosomal properties on Schistosoma mansoni. It emerged from these tests that the extracts of the stem bark and roots of A. mannii showed good activity on Schistosoma mansoni with mortality rate greater than 60%. Some compounds were shown good activity on Schistosoma mansoni, in particular gallic acid that showed zero survival rate à 100 M compared to that of praziquantel taken as an internal reference. In addition, some isolated compounds (Manniindole, Aristolactam AII, Aristolactam BII, Acide gallique, Aristolacta, BII acétylé, piperolactam D) have been tested for their inhibitory properties of the new SmNACE enzyme. This enzyme is expressed on the outer surface of Schistosoma mansoni. Some of these tested compounds were shown to be potentially active Abstract on SmNACE like piperolactam D which showed the best activity (IC50 = 10-20 μM) in comparison to the reference which is cyanidine (CI50 = 2.3 μM).