Institute Malgache Of Recherches Appliquees Imra

Antananarivo, Madagascar

Institute Malgache Of Recherches Appliquees Imra

Antananarivo, Madagascar
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Benelli G.,University of Pisa | Maggi F.,University of Camerino | Petrelli R.,University of Camerino | Canale A.,University of Pisa | And 3 more authors.
Industrial Crops and Products | Year: 2017

Malaria mortality rates have fallen by 47% globally since 2000 and by 54% in the African region, but they are still a major problem. Malaria is caused by Plasmodium parasites, vectored to people through Anopheles mosquitoes, which mainly bite between dusk and dawn. Currently, a growing number of Plasmodium species and strains developed resistance to the most commonly used anti-malarial drugs. Chloroquine (CQ), the most commonly used anti-malarial drug, actually is not effective in a number of cases, and growing Plasmodium resistance has been already observed to artemisinin. New approaches are necessary to face this challenge. One of the strategies to overcome the drug resistance in different Plasmodium species is the search for compounds known as resistance-modifiers or chemosensitizers. These compounds may restore the CQ sensitivity in CQ-resistant strains of Plasmodium. The studies started from the knowledge that some Madagascar populations use decoctions of some local plants in association with low doses of CQ to complement the CQ action against chronic malaria. In such way, resistance insurgence is lowered, as well as collateral effects. Phytochemical analyses on twelve plant species commonly used by local populations to treat malaria evidenced the presence of complex alkaloids, which showed in vitro and/or in vivo efficacy against CQ-resistant Plasmodium strains, attesting the potential use of the mix of CQ and medicinal plant preparations or compounds therein present. The approach, in accordance with recent tendencies on multidrug resistance control, is based on mixtures of natural products and classic antimalarial drugs, with a relevant coincidence between the ethnobotanical reports and the scientific evidence. © 2017 Elsevier B.V.


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.
Fitoterapia | 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-dependant RNA polymerase (RdRp) assay. The extract obtained from the leaves of Anacolosa pervilleana was selected for its significant activity in both assays. One new (E)-tridec-2-en-4-ynedioic acid named anacolosine (1), together with three known acetylenic acids, the octadeca-9,11,13-triynoic acid (2), (13E)-octadec-13-en-9,11-diynoic acid (3), (13E)-octadec-13-en-11-ynoic acid (4), two terpenoids, lupenone (5) and β-amyrone (6), and one cyanogenic glycoside, (S)-sambunigrin (7) were isolated. Their structures were elucidated by comprehensive analyses of NMR spectroscopy and mass spectrometry data. The inhibitory potency of these compounds was evaluated on CHIKV, DENV RdRp and West-Nile polymerase virus (WNV RdRp). Both terpenoids showed a moderate activity against CHIKV (EC50 77 and 86 μM, respectively) and the acetylenic acids produced IC50 values around 3 μM in the DENV RdRp assay. © 2012 Elsevier B.V. All rights reserved.


Rasamiravaka T.,University of Antananarivo | Rasamiravaka T.,Free University of Colombia | Rajaonarivelo J.P.,Free University of Colombia | Rajaonarivelo J.P.,Institute Malgache Of Recherches Appliquees Imra | And 6 more authors.
Crop Protection | Year: 2017

The control and treatment of food crops bacterial diseases remain problematic due to a scarcity of effective phytotreatments. As traditional agricultural practices may represent an attractive venue to explore new treatments, Malagasy traditional practices were investigated for their effectiveness on potato plants. A survey was conducted among Malagasy farmers to collect information on diseases observed on potato crops and on traditional disease control practices. Twelve treatments against potato bacterial diseases were tested on two potato varieties, in experimental plots naturally infected by bacterial wilt disease. The information collected from 52 farmers (i) showed that leaf spots and bacterial wilt disease are the most frequently identified threats for potato crops; and (ii) allowed to identify 12 traditional treatments among which five exhibited protective properties on potato bacterial wilt disease. Moreover, one recipe (R07) was effective on the two potato varieties after two applications per week for 10 weeks, with 50% and 72% effectiveness rate, respectively. Valorization of traditional practices may provide an effective, safe, economic and standardized phytotreatment against potato bacterial wilt disease. © 2017 Elsevier Ltd


Rasamiravaka T.,Free University of Colombia | Rasamiravaka T.,University of Antananarivo | Jedrzejowski A.,Free University of Colombia | Kiendrebeogo M.,Free University of Colombia | And 11 more authors.
Microbiology (United Kingdom) | Year: 2013

Various species of the plant genus Dalbergia are traditionally used as medicine for sundry ailments and some of them have been shown recently to quench the virulence of Gram-positive and Gram-negative bacteria. Cell-to-cell communication mechanisms, quorum sensing (QS) in particular, are key regulators of virulence in many pathogenic bacteria. Screening n-hexane extracts of leaves, roots and bark of endemic Malagasy Dalbergia species for their capacity to antagonize QS mechanisms in Pseudomonas aeruginosa PAO1 showed that many reduced the expression of the QS-regulated genes lasB and rhlA. However, only the extract of Dalbergia trichocarpa bark (DTB) showed a significant reduction of QS gene expression without any effect on the aceA gene encoding a QS-independent isocitrate lyase. Further characterization of DTB impact on QS revealed that the QS systems las and rhlare inhibited and that swarming, twitching, biofilm formation and the production of pyocyanin, elastase and proteases are also hampered in the presence of the DTB extract. Importantly, compared with the known QS inhibitor naringenin, the DTB extract showed a stronger negative effect on twitching, biofilm formation and tobramycin resistance. Preliminary structural characterization of these potent biofilm disrupters suggests that they belong to the phytosterols. The strong inhibition of motility and biofilm formation suggests that the DTB extract contains agents disrupting biofilm architecture, which is an important observation in the context of the design of new drugs targeting biofilm-encapsulated pathogens. © 2013 SGM.


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.


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.


Rafamantanana M.H.,Catholic University of Louvain | Rafamantanana M.H.,Institute Malgache Of Recherches Appliquees Imra | Debrus B.,University of Liège | 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.


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.


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.

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