Tél. : (+594) 5 94 29 26 13
Fax : (+594) 5 94 28 47 86
email : Emeline.Houel chez EcoFoG.gf
Situation actuelle
Ingénieure de Recherches à l’UMR EcoFoG.
Assistante de Prévention.
Étude de substances bioactives issues de la flore amazonienne
Depuis toujours l’homme a utilisé les plantes pour se nourrir mais aussi pour se soigner. Actuellement, de nombreux médicaments sont issus plus ou moins directement des plantes. L’étude de la biodiversité végétale dans un but de valorisation thérapeutique reste donc toujours d’actualité. Le travail effectué au cours de cette thèse porte sur ce thème et sera divisé en deux axes : l’étude de remèdes phyothérapeutiques antipaludiques et la recherche de nouvelles huiles essentielles antifongiques. Ces études seront focalisées sur la flore guyanaise.
La Guyane française est une région où sévit le paludisme de manière endémique. Au cours des siècles, ses habitants ont développé une pharmacopée à base de plantes pour se prémunir et soigner des affections de tout genre y compris le paludisme. Le remède fébrifuge le plus répandu dans tout le tout le Nord-Est du bassin amazonien, est une simple tisane faite à partir de feuilles matures d’une Simaroubaceae, Quassia amara L.. Nous avons étudié la composition chimique de tisanes de Quassia amara ainsi que l’activité des molécules isolées. Une seconde préparation, une décoction à base de feuilles et de tiges de Psidium acutangulum DC (Myrtaceae), remède localisé à la communauté Wayana du Haut-Maroni, est également étudiée.
D’un autre côté, au niveau mondial mais aussi en particulier en Guyane, l’incidence des infections fongiques est en pleine augmentation, du fait d’un nombre croissant de patients à haut risque et du développement des résistances. Ces faits, couplés à une toxicité des traitements actuels sur le long terme et à une faible biodisponibilté conduisent à la poursuite de la recherche de nouveaux traitements, en particulier dans le domaine des substances naturelles. Le but de cette étude est d’identifier de nouvelles huiles essentielles présentant des propriétés antifongiques vis-à-vis de plusieurs souches de champignons dermatophytes et de levures provoquant des mycoses chez l’homme.
Mots-clés : champignons, parasites, chimie des substances naturelles, huiles essentielles, remèdes traditionnels.
Publications pour EcoFoG
Houel, E., et al. "Wayanin and guaijaverin, two active metabolites found in a Psidium acutangulum Mart. ex DC (syn. P. persoonii McVaugh) (Myrtaceae) antimalarial decoction from the Wayana Amerindians." Journal of Ethnopharmacology. 187 (2016): 241–248.
Abstract: Ethnopharmacological relevance Psidium acutangulum Mart. ex DC is a small tree used by the Wayana Amerindians from the Upper-Maroni in French Guiana for the treatment of malaria. Aim of the study In a previous study, we highlighted the in vitro antiplasmodial, antioxidant and anti-inflammatory potential of the traditional decoction of P. acutangulum aerial parts. Our goal was then to investigate on the origin of the biological activity of the traditional remedy, and eventually characterize active constituents. Materials and methods Liquid-liquid extractions were performed on the decoction, and the antiplasmodial activity evaluated against chloroquine-resistant FcB1 ([3H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains, and on a chloroquine sensitive NF54 ([3H]-hypoxanthine bioassay) P. falciparum strain. The ethyl acetate fraction (D) was active and underwent bioguided fractionation. All the isolated compounds were tested on P. falciparum FcB1 strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) of the ethyl acetate fraction and of an anti-Plasmodium active compound, was concurrently assessed on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the fractions and pure compounds was measured on VERO cells, L6 mammalian cells, PBMCs, and RAW cells. Results Fractionation of the ethyl acetate soluble fraction (IC50 ranging from 3.4 to <1 μg/mL depending on the parasite strain) led to the isolation of six pure compounds: catechin and five glycosylated quercetin derivatives. These compounds have never been isolated from this plant species. Two of these compounds (wayanin and guaijaverin) were found to be moderately active against P. falciparum FcB1 in vitro (IC50 5.5 and 6.9 μM respectively). We proposed the name wayanin during public meetings organized in June 2015 in the Upper-Maroni villages, in homage to the medicinal knowledge of the Wayana population. At 50 μg/mL, the ethyl acetate fraction (D) significantly inhibited IL-1β secretion (-46%) and NO production (-21%), as previously observed for the decoction. The effects of D and guiajaverin (4) on the secretion of other cytokines or NO production were not significant. Conclusions The confirmed antiplasmodial activity of the ethyl acetate soluble fraction of the decoction and of the isolated compounds support the previous results obtained on the P. acutangulum decoction. The antiplasmodial activity might be due to a mixture of moderately active non-toxic flavonoids. The anti-inflammatory activities were less marked for ethyl acetate fraction (D) than for the decoction. © 2016 Elsevier Ireland Ltd. All rights reserved.
Keywords: Antimalarial; Cytokines; French guiana; Glycosylated flavonols; Psidium acutangulum; Traditional remedy
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Houel, E., et al. "Antiplasmodial and anti-inflammatory effects of an antimalarial remedy from the Wayana Amerindians, French Guiana: Takamalaimë (Psidium acutangulum Mart. ex DC., Myrtaceae)." Journal of Ethnopharmacology. 166 (2015): 279–285.
Abstract: Ethnopharmacological relevance:
Field investigations highlighted the use of Psidium acutangulum Mart. ex DC (syn. P. persoonii McVaugh), a small tree used by the Wayana Amerindians in Twenke–Taluhwen and Antecume–Pata, French Guiana, for the treatment of malaria, and administered either orally in the form of a decoction or applied externally over the whole body. This use appears limited to the Wayana cultural group in French Guiana and has never been reported anywhere else. Our goal was to evaluate the antimalarial and anti-inflammatory activities of a P. acutangulum decoction to explain the good reputation of this remedy.
Materials and methods:
Interviews with the Wayana inhabitants of Twenke–Taluhwen and Antecume–Pata were conducted within the TRAMAZ project according to the TRAMIL methodology, which is based on a quantitative and qualitative analysis of medicinal plant uses. A decoction of dried aerial parts of P. acutangulum was prepared in consistency with the Wayana recipe. In vitro antiplasmodial assays were performed on chloroquine-resistant FcB1 ([3H]-hypoxanthine bioassay) and 7G8 (pLDH bioassay) P. falciparum strains and on chloroquine sensitive NF54 ([3H]-hypoxanthine bioassay) P. falciparum strain. In vitro anti-inflammatory activity (IL-1β, IL-6, IL-8, TNFα) was evaluated on LPS-stimulated human PBMC and NO secretion inhibition was measured on LPS stimulated RAW murine macrophages. Cytotoxicity of the decoction was measured on L6 mammalian cells, PBMCs, and RAW cells. A preliminary evaluation of the in vivo antimalarial activity of the decoction, administered orally twice daily, was assessed by the classical four-day suppressive test against P. berghei NK65 in mice.
Results:
The decoction displayed a good antiplasmodial activity in vitro against the three tested strains, regardless to the bioassay used, with IC50 values of 3.3 µg/mL and 10.3 µg/mL against P. falciparum FcB1 and NF54, respectively and 19.0 µg/mL against P. falciparum 7G8. It also exhibited significant anti-inflammatory activity in vitro in a dose dependent manner. At a concentration of 50 µg/mL, the decoction inhibited the secretion of the following pro-inflammatory cytokines: TNFα (−18%), IL-1β (−58%), IL-6 (−32%), IL-8 (−21%). It also exhibited a mild NO secretion inhibition (−13%) at the same concentration. The decoction was non-cytotoxic against L6 cells (IC50>100 µg/mL), RAW cells and PBMC. In vivo, 150 µL of the decoction given orally twice a day (equivalent to 350 mg/kg/day of dried extract) inhibited 39.7% average parasite growth, with more than 50% of inhibition in three mice over five. The absence of response for the two remaining mice, however, induced a strong standard deviation.
Conclusions:
This study highlighted the in vitro antiplasmodial activity of the decoction of P. acutangulum aerial parts, used by Wayana Amerindians from the Upper-Maroni in French Guiana in case of malaria. Its antioxidant and anti-inflammatory potential, which may help to explain its use against this disease, was demonstrated using models of artificially stimulated cells.
Keywords: Psidium acutangulum; Plasmodium; Cytokines; Antimalarial; French Guiana; Traditional medicine
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Houel, E., et al. "Therapeutic switching: From antidermatophytic essential oils to new leishmanicidal products." Memorias do Instituto Oswaldo Cruz. 110.1 (2015): 106–11(PU%MEQTUUQUIM`UUTA$PUU]]U@aFMYEa=sQee\X,KQVOUCUM@U=U=4AQ]SL5E<`QUATaEAQsAQEDQPTO\QuDUUED@Qau<TMX-uO\QaB]PPTKAPUAuQaFMUVeRaAEXP]DaEaETECPaSdP-PaBPaFTEFPA%AKQWQsaQX1U]QAuQ]-R="=]PUDQQSPURPU=U=V=
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Houel, E., et al. "In vitro antidermatophytic activity of Otacanthus azureus (Linden) Ronse essential oil alone and in combination with azoles." J. Appl. Microbiol.. 116.2 (2014): 288–294.
Abstract: Aims: We determined the chemical composition and investigated the antifungal activity of Otacanthus azureus (Linden) Ronse essential oil (EO) against a range of dermatophytes alone or in combination with azole antifungals. Methods and Results: Aerial parts of the plant were steam-distilled and the obtained oil was analysed by gas chromatography/mass spectrometry and 1H-NMR. It was shown to be largely composed of sesquiterpenes, with the main component being β-copaen-4-α-ol. Using broth microdilution techniques, this oil was found to have remarkable in vitro antifungal activities. Minimum inhibitory concentrations as low as 4 μg ml-1 were recorded. The analysis of the combined effect of the O. azureus EO with azoles using chequerboard assays revealed a synergism between the EO and ketoconazole, fluconazole or itraconazole against Trichophyton mentagrophytes. Notably, the O. azureus essential oil showed low cytotoxicity to VERO cells. Conclusions: The O. azureus essential oil alone or in combination with azoles is a promising antifungal agent in the treatment for human dermatomycoses caused by filamentous fungi. Significance and Impact of the Study: There is much interest in the study of essential oils for the discovery of new antimicrobial drugs. This study has highlighted the antidermatophytic activity of the O. azureus EO. © 2013 The Society for Applied Microbiology.
Keywords: Antifungal activity; Azoles; Dermatophytes; Essential oil; Otacanthus azureus; Synergy
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Courtois, E. A., et al. "Differences in volatile terpene composition between the bark and leaves of tropical tree species." Phytochemistry. 82 (2012): 81–88.
Abstract: Volatile terpenes are among the most diverse class of defensive compounds in plants, and they are implicated in both direct and indirect defense against herbivores. In terpenes, both the quantity and the diversity of compounds appear to increase the efficiency of defense as a diverse blend of compounds provides a more efficient protection against a broader range of herbivores and limits the chances that an enemy evolves resistance. Theory predicts that plant defensive compounds should be allocated differentially among tissues according to the value of the tissue, its cost of construction and the herbivore pressure on it. We collected volatile terpenes from bark and leaves of 178 individual tree belonging to 55 angiosperm species in French Guiana and compare the kind, amount, and diversity of compounds in these tissues. We hypothesized that in woody plants, the outermost part of the trunk should hold a more diverse blend of volatile terpenes. Additionally, as herbivore communities associated with the leaves is different to the one associated with the bark, we also hypothesized that terpene blends should be distinct in the bark vs. the leaves of a given species. We found that the mixture of volatile terpenes released by bark is different and more diverse than that released by leaves, both in monoterpenes and sesquiterpenes. This supports our hypothesis and further suggests that the emission of terpenes by the bark should be more important for trunk defense than previously thought. © 2012 Elsevier Ltd. All rights reserved.
Keywords: French Guiana; Herbivory; Optimal defense theory; Secondary metabolites; Wood
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