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Rajaonson S.,Free University of Colombia | Rajaonson S.,University of Antananarivo | Vandeputte O.M.,Free University of Colombia | Vereecke D.,University College Ghent | And 10 more authors.
Environmental Microbiology | Year: 2011

The phytopathogenic Actinomycete Rhodococcus fascians induces leafy galls on a wide range of hosts, causing major economical losses in the ornamentals industry. Although differences in the responsivity occur within species, no plant tested so far could be considered resistant to R. fascians strain D188 infection. Here, we observed that members of the genus Dalbergia, which belong to the Fabaceae, did not develop leafy galls when challenged with R. fascians and we set out to unravel the mechanism of this recalcitrance. Whereas organic extracts of Dalbergia tissues exhibited toxicity towards the bacteria, more importantly, dichloromethane bark extracts inhibited the induction of bacterial virulence gene expression without any apparent loss of viability, illustrating that resistance is likely multifactorial. The virulence quencher was identified as a new prenylated isoflavanone, termed perbergin, and specifically targeted the AttR regulon (a LysR-type transcriptional regulator) which is imperative for the switch of R. fascians from an epiphytic to a pathogenic lifestyle. The mode of action of perbergin demonstrated that just like in Gram-negative host-microbe interactions, also in Gram-positive phytopathogens autoregulation is being targeted by the plant as an efficient means of defence. Moreover, the identification of perbergin opens the path to disease control in affected nurseries. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd. Source

Bourjot M.,CNRS Natural Product Chemistry Institute | Leyssen P.,Rega Institute for Medical Research | Eydoux C.,Laboratoire Darchitecture Et Of Fonction Des Macromolecules Biologiques Afmb Amu Umr7257 | Guillemot J.-C.,Laboratoire Darchitecture Et Of Fonction Des Macromolecules Biologiques Afmb Amu Umr7257 | And 4 more authors.
Journal of Natural Products | Year: 2012

In an effort to identify novel inhibitors of chikungunya (CHIKV) and dengue (DENV) virus replication, a systematic study with 820 ethyl acetate extracts of madagascan plants was performed in a virus-cell-based assay for CHIKV, and a DENV NS5 RNA-dependent RNA polymerase (RdRp) assay. The extract obtained from the stem bark of Flacourtia ramontchi was selected for its significant activity in both assays. Six new phenolic glycosides, named flacourtosides A-F (1-6), phenolic glycosides itoside H, xylosmin, scolochinenoside D, and poliothrysoside, and betulinic acid 3β-caffeate were obtained using the bioassay-guided isolation process. Their structures were elucidated by comprehensive analyses of NMR spectroscopic and mass spectrometric data. Even though several extracts and fractions showed significant selective antiviral activity in the CHIKV virus-cell-based assay, none of the purified compounds did. However, in the DENV RNA polymerase assay, significant inhibition was observed with betulinic acid 3β-caffeate (IC50 = 0.85 ± 0.1 μM) and to a lesser extent for the flacourtosides A and E (1 and 5, respectively), and scolochinenoside D (IC50 values ∼10 μM). © 2012 The American Chemical Society and American Society of Pharmacognosy. Source

Rabehaja D.J.R.,Institute Malgache Of Recherches Appliquees Imra | Rabehaja D.J.R.,CNRS Environmental Sciences | Raoelison G.,Institute Malgache Of Recherches Appliquees Imra | Ihandriharison H.,Institute Malgache Of Recherches Appliquees Imra | And 3 more authors.
Journal of Essential Oil-Bearing Plants | Year: 2010

The composition of essential oil isolated by hydrodistillation (Clevenger type apparatus) and by vapour distillation (industrial-scale equipment) from the aerial parts of Cymbopogon giganteus (Hochst) Chiov. var. madagascariensis (A. Camus) growing wild in South-Western Madagascar was investigated by GC (RI), GC-MS and 13C NMR. The composition of the Malgasy oil, dominated by p-menthadienol isomers and limonene, is similar to that of African C. giganteus oils. Source

Raoelison G.E.,Institute Malgache Of Recherches Appliquees | Rafamantanana M.H.,Institute Malgache Of Recherches Appliquees | Rafamantanana M.H.,Catholic University of Louvain | Razafindrazaka R.,Institute Malgache Of Recherches Appliquees Imra | And 5 more authors.
Natural Product Communications | Year: 2013

Spirospermum penduliflorum Thouars (Menispermaceae) is widely used on the eastern coast of Madagascar to treat hypertension. The aim of the present study was to analyse the vasorelaxant properties of different leaf extracts. The activity of the n-hexane, dichloromethane and methanolic extracts was tested on phenylephrine-contracted aorta. The dichloromethane extract was shown to be the most effective. Further fractionation of this extract led to the isolation of an active fraction relaxing phenylephrine-contracted aorta with an IC50 of 0.18 μg/mL {log IC50 (μg/mL) -0.74 ± 0.03} but was much less effective on KCl induced contractions. Bioassay-guided fractionation of this fraction led to the isolation of two aporphinoid alkaloids, neolitsine and dicentrine, which at concentrations of 0.1 μM and 1 μM displaced to the right the phenylephrine concentration-contraction curve. Our results show that Spirospermum penduliflorum extracts possess vasorelaxant activity in vitro that could be related to the presence of dicentrine in the extracts having an a1 antagonist activity. This finding is not in accord with the previous studies by Rasoanaivo et al. where no alkaloids were detected in the leaves of Spirospermum penduliflorum. Keywords: Spirospermum penduliflorum, Menispermaceae, Aporphine alkaloids, Antihypertensive activity. Source

Rafamantanana M.H.,Catholic University of Louvain | Rafamantanana M.H.,Institute Malgache Of Recherches Appliquees Imra | Debrus B.,University of Liege | Raoelison G.E.,Institute Malgache Of Recherches Appliquees Imra | And 5 more authors.
Journal of Pharmaceutical and Biomedical Analysis | Year: 2012

Spirospermum penduliflorum Thouars (Menispermaceae) is an endemic species of Madagascar traditionally used as vasorelaxant. Recently, two aporphine alkaloids known to possess antihypertensive activity (dicentrine and neolitsine) were isolated and identified from the leaves of this plant. In the present study, a HPLC-UV method allowing the separation of all alkaloids and the quantification of dicentrine in the alkaloidic extract of leaves was developed using design of experiments and design space methodology. Three common chromatographic parameters (i.e. the mobile phase pH, the initial proportion of methanol and the gradient slope) were selected to construct a full factorial design of 36 experimental conditions. The times at the beginning, the apex (i.e. the retention time) and the end of each peak were recorded and modelled by multiple linear equations. The corresponding residuals were normally distributed which confirmed that the models can be used for the prediction of the retention times and to optimize the separation. The optimal separation was predicted at pH 3, with a gradient starting at 32% of methanol and a gradient slope of 0.42%/min. Good agreement was obtained between predicted and experimental chromatograms. The method was also validated using total error concept. Using the accuracy profile approach, validation results gave a LOD and LOQ for dicentrine of 3 μg/ml and 10 μg/ml, respectively. A relative standard deviation for intermediate precision lower than 10% was obtained. This method was found to provide accurate results in the concentration range of 10-75 μg/ml of dicentrine and is suitable for routine analysis. © 2012 Elsevier B.V. Source

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