Publications by authors named "Christophe Duplais"

33 Publications

Cardenolides, toxicity, and the costs of sequestration in the coevolutionary interaction between monarchs and milkweeds.

Proc Natl Acad Sci U S A 2021 Apr;118(16)

CNRS, UMR8172 Ecologie des Forêts de Guyane, AgroParisTech, Cirad, INRAE, Université des Antilles, Université de Guyane, Campus agronomique, 97379 Kourou, French Guiana, France.

For highly specialized insect herbivores, plant chemical defenses are often co-opted as cues for oviposition and sequestration. In such interactions, can plants evolve novel defenses, pushing herbivores to trade off benefits of specialization with costs of coping with toxins? We tested how variation in milkweed toxins (cardenolides) impacted monarch butterfly () growth, sequestration, and oviposition when consuming tropical milkweed (), one of two critical host plants worldwide. The most abundant leaf toxin, highly apolar and thiazolidine ring-containing voruscharin, accounted for 40% of leaf cardenolides, negatively predicted caterpillar growth, and was not sequestered. Using whole plants and purified voruscharin, we show that monarch caterpillars convert voruscharin to calotropin and calactin in vivo, imposing a burden on growth. As shown by in vitro experiments, this conversion is facilitated by temperature and alkaline pH. We next employed toxin-target site experiments with isolated cardenolides and the monarch's neural Na/K-ATPase, revealing that voruscharin is highly inhibitory compared with several standards and sequestered cardenolides. The monarch's typical >50-fold enhanced resistance to cardenolides compared with sensitive animals was absent for voruscharin, suggesting highly specific plant defense. Finally, oviposition was greatest on intermediate cardenolide plants, supporting the notion of a trade-off between benefits and costs of sequestration for this highly specialized herbivore. There is apparently ample opportunity for continued coevolution between monarchs and milkweeds, although the diffuse nature of the interaction, due to migration and interaction with multiple milkweeds, may limit the ability of monarchs to counteradapt.
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http://dx.doi.org/10.1073/pnas.2024463118DOI Listing
April 2021

Gut bacteria are essential for normal cuticle development in herbivorous turtle ants.

Nat Commun 2021 01 29;12(1):676. Epub 2021 Jan 29.

Department of Entomology and Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA.

Across the evolutionary history of insects, the shift from nitrogen-rich carnivore/omnivore diets to nitrogen-poor herbivorous diets was made possible through symbiosis with microbes. The herbivorous turtle ants Cephalotes possess a conserved gut microbiome which enriches the nutrient composition by recycling nitrogen-rich metabolic waste to increase the production of amino acids. This enrichment is assumed to benefit the host, but we do not know to what extent. To gain insights into nitrogen assimilation in the ant cuticle we use gut bacterial manipulation, N isotopic enrichment, isotope-ratio mass spectrometry, and N nuclear magnetic resonance spectroscopy to demonstrate that gut bacteria contribute to the formation of proteins, catecholamine cross-linkers, and chitin in the cuticle. This study identifies the cuticular components which are nitrogen-enriched by gut bacteria, highlighting the role of symbionts in insect evolution, and provides a framework for understanding the nitrogen flow from nutrients through bacteria into the insect cuticle.
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http://dx.doi.org/10.1038/s41467-021-21065-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7846594PMC
January 2021

Heterodimeric Insecticidal Peptide Provides New Insights into the Molecular and Functional Diversity of Ant Venoms.

ACS Pharmacol Transl Sci 2020 Dec 6;3(6):1211-1224. Epub 2020 Oct 6.

CNRS, UMR Ecofog, AgroParisTech, Cirad, INRAE, Université des Antilles, Université de Guyane, Kourou 97310, France.

Ants use venom for predation, defense, and communication; however, the molecular diversity, function, and potential applications of ant venom remains understudied compared to other venomous lineages such as arachnids, snakes and cone snails. In this work, we used a multidisciplinary approach that encompassed field work, proteomics, sequencing, chemical synthesis, structural analysis, molecular modeling, stability studies, and and bioassays to investigate the molecular diversity of the venom of the Amazonian ants. We isolated a potent insecticidal heterodimeric peptide Δ-pseudomyrmecitoxin-Pp1a (Δ-PSDTX-Pp1a) composed of a 27-residue long A-chain and a 33-residue long B-chain cross-linked by two disulfide bonds in an antiparallel orientation. We chemically synthesized Δ-PSDTX-Pp1a, its corresponding parallel AA and BB homodimers, and its monomeric chains and demonstrated that Δ-PSDTX-Pp1a had the most potent insecticidal effects in blowfly assays (LD = 3 nmol/g). Molecular modeling and circular dichroism studies revealed strong α-helical features, indicating its cytotoxic effects could derive from cell membrane pore formation or disruption. The native heterodimer was substantially more stable against proteolytic degradation ( = 13 h) than its homodimers or monomers ( < 20 min), indicating an evolutionary advantage of the more complex structure. The proteomic analysis of venom and in-depth characterization of Δ-PSDTX-Pp1a provide novel insights in the structural complexity of ant venom and further exemplifies how nature exploits disulfide-bond formation and dimerization to gain an evolutionary advantage via improved stability, a concept that is highly relevant for the design and development of peptide therapeutics, molecular probes, and bioinsecticides.
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http://dx.doi.org/10.1021/acsptsci.0c00119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7737211PMC
December 2020

Tracking the Origin and Evolution of Plant Metabolites.

Trends Plant Sci 2020 12 4;25(12):1182-1184. Epub 2020 Sep 4.

Biomolécules et Biotechnologies Végétales (BBV) EA 2106, Université de Tours, Tours, France. Electronic address:

Iridoids are monoterpenes that are produced by various plants as chemical defense molecules. Lichman et al. recently described the timeline of molecular events that underpin the re-emergence of iridoid biosynthesis in an independent lineage of aromatic plants (catnip). This study represents a benchmark for studying enzyme and metabolite evolution in different clades across the tree of life.
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http://dx.doi.org/10.1016/j.tplants.2020.08.010DOI Listing
December 2020

Development but not diet alters microbial communities in the Neotropical arboreal trap jaw ant Daceton armigerum: an exploratory study.

Sci Rep 2020 04 30;10(1):7350. Epub 2020 Apr 30.

Cornell University, Department of Entomology, Ithaca, NY, 14850, USA.

To better understand the evolutionary significance of symbiotic interactions in nature, microbiome studies can help to identify the ecological factors that may shape host-associated microbial communities. In this study we explored both 16S and 18S rRNA microbial communities of D. armigerum from both wild caught individuals collected in the Amazon and individuals kept in the laboratory and fed on controlled diets. We also investigated the role of colony, sample type, development and caste on structuring microbial communities. Our bacterial results (16S rRNA) reveal that (1) there are colony level differences between bacterial communities; (2) castes do not structure communities; (3) immature stages (brood) have different bacterial communities than adults; and 4) individuals kept in the laboratory with a restricted diet showed no differences in their bacterial communities from their wild caught nest mates, which could indicate the presence of a stable and persistent resident bacterial community in this host species. The same categories were also tested for microbial eukaryote communities (18S rRNA), and (5) developmental stage has an influence on the diversity recovered; (6) the diversity of taxa recovered has shown this can be an important tool to understand additional aspects of host biology and species interactions.
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http://dx.doi.org/10.1038/s41598-020-64393-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7192945PMC
April 2020

Disentangling the assembly mechanisms of ant cuticular bacterial communities of two Amazonian ant species sharing a common arboreal nest.

Mol Ecol 2020 04 23;29(7):1372-1385. Epub 2020 Mar 23.

CNRS, UMR8172 EcoFoG, AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, Cayenne, France.

Bacteria living on the cuticle of ants are generally studied for their protective role against pathogens, especially in the clade of fungus-growing ants. However, little is known regarding the diversity of cuticular bacteria in other ant host species, as well as the mechanisms leading to the composition of these communities. Here, we used 16S rRNA gene amplicon sequencing to study the influence of host species, species interactions and the pool of bacteria from the environment on the assembly of cuticular bacterial communities on two phylogenetically distant Amazonian ant species that frequently nest together inside the roots system of epiphytic plants, Camponotus femoratus and Crematogaster levior. Our results show that (a) the vast majority of the bacterial community on the cuticle is shared with the nest, suggesting that most bacteria on the cuticle are acquired through environmental acquisition, (b) 5.2% and 2.0% of operational taxonomic units (OTUs) are respectively specific to Ca. femoratus and Cr. levior, probably representing their respective core cuticular bacterial community, and (c) 3.6% of OTUs are shared between the two ant species. Additionally, mass spectrometry metabolomics analysis of metabolites on the cuticle of ants, which excludes the detection of cuticular hydrocarbons produced by the host, were conducted to evaluate correlations among bacterial OTUs and m/z ion mass. Although some positive and negative correlations are found, the cuticular chemical composition was weakly species-specific, suggesting that cuticular bacterial communities are prominently environmentally acquired. Overall, our results suggest the environment is the dominant source of bacteria found on the cuticle of ants.
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http://dx.doi.org/10.1111/mec.15400DOI Listing
April 2020

Biosynthetic investigation of γ-lactones in Sextonia rubra wood using in situ TOF-SIMS MS/MS imaging to localize and characterize biosynthetic intermediates.

Sci Rep 2019 02 13;9(1):1928. Epub 2019 Feb 13.

CNRS UMR8172 EcoFoG, AgroParisTech, CIRAD, INRA, Université des Antilles, Université de Guyane, 97300, Cayenne, France.

Molecular analysis by parallel tandem mass spectrometry (MS/MS) imaging contributes to the in situ characterization of biosynthetic intermediates which is crucial for deciphering the metabolic pathways in living organisms. We report the first use of TOF-SIMS MS/MS imaging for the cellular localization and characterization of biosynthetic intermediates of bioactive γ-lactones rubrynolide and rubrenolide in the Amazonian tree Sextonia rubra (Lauraceae). Five γ-lactones, including previously reported rubrynolide and rubrenolide, were isolated using a conventional approach and their structural characterization and localization at a lateral resolution of ~400 nm was later achieved using TOF-SIMS MS/MS imaging analysis. 2D/3D MS imaging at subcellular level reveals that putative biosynthetic γ-lactones intermediates are localized in the same cell types (ray parenchyma cells and oil cells) as rubrynolide and rubrenolide. Consequently, a revised metabolic pathway of rubrynolide was proposed, which involves the reaction between 2-hydroxysuccinic acid and 3-oxotetradecanoic acid, contrary to previous studies suggesting a single polyketide precursor. Our results provide insights into plant metabolite production in wood tissues and, overall, demonstrate that combining high spatial resolution TOF-SIMS imaging and MS/MS structural characterization offers new opportunities for studying molecular and cellular biochemistry in plants.
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http://dx.doi.org/10.1038/s41598-018-37577-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374367PMC
February 2019

Tandem Mass Spectrometry Imaging and in Situ Characterization of Bioactive Wood Metabolites in Amazonian Tree Species Sextonia rubra.

Anal Chem 2018 06 8;90(12):7535-7543. Epub 2018 Jun 8.

Institut de Chimie des Substances Naturelles , CNRS UPR 2301, Univ. Paris-Sud, Université Paris-Saclay , Avenue de la Terrasse , 91198 Gif-sur-Yvette , France.

Driven by a necessity for confident molecular identification at high spatial resolution, a new time-of-flight secondary ion mass spectrometry (TOF-SIMS) tandem mass spectrometry (tandem MS) imaging instrument has been recently developed. In this paper, the superior MS/MS spectrometry and imaging capability of this new tool is shown for natural product study. For the first time, via in situ analysis of the bioactive metabolites rubrynolide and rubrenolide in Amazonian tree species Sextonia rubra (Lauraceae), we were able both to analyze and to image by tandem MS the molecular products of natural biosynthesis. Despite the low abundance of the metabolites in the wood sample(s), efficient MS/MS analysis of these γ-lactone compounds was achieved, providing high confidence in the identification and localization. In addition, tandem MS imaging minimized the mass interferences and revealed specific localization of these metabolites primarily in the ray parenchyma cells but also in certain oil cells and, further, revealed the presence of previously unidentified γ-lactone, paving the way for future studies in biosynthesis.
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http://dx.doi.org/10.1021/acs.analchem.8b01157DOI Listing
June 2018

Tandem Biocatalysis Unlocks the Challenging de Novo Production of Plant Natural Products.

Chembiochem 2017 11 27;18(22):2192-2195. Epub 2017 Oct 27.

CNRS, UMR8172 EcoFoG, AgroParisTech, Cirad, INRA, Université des Antilles, Université de Guyane, Campus agronomique avenue de France, 97379, Kourou, French Guiana, France.

Intimate partnership: Knowledge of the biocatalytic cascades in different cellular compartments is limited, but deciphering these systems in nature can be used to inspire synthetic strategies. Two studies report new insights into the biosynthesis of alkaloids and sesterterpenoids in plants. This highlight presents these novel biotransformations to illustrate how tandem biocatalysis can impact the future of natural product production.
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http://dx.doi.org/10.1002/cbic.201700508DOI Listing
November 2017

Antiplasmodial activities of dyes against Plasmodium falciparum asexual and sexual stages: Contrasted uptakes of triarylmethanes Brilliant green, Green S (E142), and Patent Blue V (E131) by erythrocytes.

Int J Parasitol Drugs Drug Resist 2017 12 2;7(3):314-320. Epub 2017 Aug 2.

CNRS, UMR8172 EcoFoG, AgroParisTech, Cirad, INRA, Université des Antilles, Université de Guyane, 97300 Cayenne, French Guiana, France. Electronic address:

The search for safe antimalarial compounds acting against asexual symptom-responsible stages and sexual transmission-responsible forms of Plasmodium species is one of the major challenges in malaria elimination programs. So far, among current drugs approved for human use, only primaquine has transmission-blocking activity. The discovery of small molecules targeting different Plasmodium falciparum life stages remains a priority in antimalarial drug research. In this context, several independent studies have recently reported antiplasmodial and transmission-blocking activities of commonly used stains, dyes and fluorescent probes against P. falciparum including chloroquine-resistant isolates. Herein we have studied the antimalarial activities of dyes with different scaffold and we report that the triarylmethane dye (TRAM) Brilliant green inhibits the growth of asexual stages (IC ≤ 2 μM) and has exflagellation-blocking activity (IC ≤ 800 nM) against P. falciparum reference strains (3D7, 7G8) and chloroquine-resistant clinical isolate (Q206). In a second step we have investigated the antiplasmodial activities of two polysulfonated triarylmethane food dyes. Green S (E142) is weakly active against P. falciparum asexual stage (IC ≃ 17 μM) whereas Patent Blue V (E131) is inactive in both antimalarial assays. By applying liquid chromatography techniques for the culture supernatant analysis after cell washings and lysis, we report the detection of Brilliant green in erythrocytes, the selective uptake of Green S (E142) by infected erythrocytes, whereas Patent Blue V (E131) could not be detected within non-infected and 3D7-infected erythrocytes. Overall, our results suggest that two polysulfonated food dyes might display different affinity with transporters or channels on infected RBC membrane.
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http://dx.doi.org/10.1016/j.ijpddr.2017.07.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5587875PMC
December 2017

Comparative analysis of DNA extraction methods to study the body surface microbiota of insects: A case study with ant cuticular bacteria.

Mol Ecol Resour 2017 Nov 21;17(6):e34-e45. Epub 2017 Jun 21.

CNRS, UMR8172 EcoFoG, AgroParisTech, Cirad, INRA, Université des Antilles, Université de Guyane, Cayenne, France.

High-throughput sequencing of the 16S rRNA gene has considerably helped revealing the essential role of bacteria living on insect cuticles in the ecophysiology and behaviour of their hosts. However, our understanding of host-cuticular microbiota feedbacks remains hampered by the difficulties of working with low bacterial DNA quantities as with individual insect cuticle samples, which are more prone to molecular biases and contaminations. Herein, we conducted a methodological benchmark on the cuticular bacterial loads retrieved from two Neotropical ant species of different body size and ecology: Atta cephalotes (~15 mm) and Pseudomyrmex penetrator (~5 mm). We evaluated the richness and composition of the cuticular microbiota, as well as the amount of biases and contamination produced by four DNA extraction protocols. We also addressed how bacterial community characteristics would be affected by the number of individuals or individual body size used for DNA extraction. Most extraction methods yielded similar results in terms of bacterial diversity and composition for A. cephalotes (~15 mm). In contrast, greater amounts of artefactual sequences and contaminations, as well as noticeable differences in bacterial community characteristics were observed between extraction methods for P. penetrator (~5 mm). We also found that large (~15 mm) and small (~5 mm) A. cephalotes individuals harbour different bacterial communities. Our benchmark suggests that cuticular microbiota of single individual insects can be reliably retrieved provided that blank controls, appropriate data cleaning, and individual body size and functional role within insect society are considered in the experiment.
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http://dx.doi.org/10.1111/1755-0998.12688DOI Listing
November 2017

Correction: Fluorescent natural products as probes and tracers in biology.

Nat Prod Rep 2017 03;34(3):329

CNRS, UMR 8172 EcoFoG (Ecologie des Forêts de Guyane), AgroParisTech, Cirad, INRA, Université des Antilles, Université de Guyane, 23 avenue Pasteur, 97300 Cayenne, France.

Correction for 'Fluorescent natural products as probes and tracers in biology' by Romain Duval et al., Nat. Prod. Rep., 2017, DOI: 10.1039/c6np00111d.
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http://dx.doi.org/10.1039/c7np90008bDOI Listing
March 2017

Revisiting Previously Investigated Plants: A Molecular Networking-Based Study of Geissospermum laeve.

J Nat Prod 2017 04 10;80(4):1007-1014. Epub 2017 Mar 10.

Équipe "Pharmacognosie-Chimie des Substances Naturelles" BioCIS, Univ. Paris-Sud, CNRS, Université Paris-Saclay , 5 Rue J.-B. Clément, 92290 Châtenay-Malabry, France.

Three new monoterpene indole alkaloids (1-3) have been isolated from the bark of Geissospermum laeve, together with the known alkaloids (-)-leuconolam (4), geissolosimine (5), and geissospermine (6). The structures of 1-3 were elucidated by analysis of their HRMS and NMR spectroscopic data. The absolute configuration of geissolaevine (1) was deduced from the comparison of experimental and theoretically calculated ECD spectra. The isolation workflow was guided by a molecular networking-based dereplication strategy using an in-house database of monoterpene indole alkaloids. In addition, five known compounds previously undescribed in the Geissospermum genus were dereplicated from the G. laeve alkaloid extract network and were assigned with various levels of identification confidence. The antiparasitic activities against Plasmodium falciparum and Leishmania donovani as well as the cytotoxic activity against the MRC-5 cell line were determined for compounds 1-5.
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http://dx.doi.org/10.1021/acs.jnatprod.6b01013DOI Listing
April 2017

Fluorescent natural products as probes and tracers in biology.

Nat Prod Rep 2017 Feb 26;34(2):161-193. Epub 2017 Jan 26.

IRD, UMR 216 IRD MERIT (Mère et Enfant face aux Infections Tropicales), Université Paris-Descartes, 4 Avenue de l'Observatoire, 75006 Paris, France.

Covering: 1985 up to the end of 2016Fluorescence is a remarkable property of many natural products in addition to their medicinal and biological values. Herein, we provide a review on these peculiar secondary metabolites to stimulate prospecting of them as original fluorescent tracers, endowed with unique photophysical properties and with applications in most fields of biology. The compounds are spectrally categorized (i.e. fluorescing from violet to the near infra-red) and further structurally classified within each category. Natural products selected for their high impact in modern fluorescence-based biological studies are highlighted throughout the article. Finally, we discuss aspects of chemical ecology where fluorescent natural products might have key evolutionary roles and thus open new research directions in the field.
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http://dx.doi.org/10.1039/c6np00111dDOI Listing
February 2017

New Insights on Wood Dimensional Stability Influenced by Secondary Metabolites: The Case of a Fast-Growing Tropical Species Bagassa guianensis Aubl.

PLoS One 2016 23;11(3):e0150777. Epub 2016 Mar 23.

CNRS, UMR EcoFoG, AgroParisTech, Cirad, INRA, Université des Antilles, Université de Guyane, 97310 Kourou, France.

Challenging evaluation of tropical forest biodiversity requires the reporting of taxonomic diversity but also the systematic characterization of wood properties in order to discover new promising species for timber industry. Among wood properties, the dimensional stability is regarded as a major technological characteristic to validate whether a wood species is adapted to commercial uses. Cell structure and organization are known to influence the drying shrinkage making wood density and microfibrils angle markers of choice to predict wood dimensional stability. On the contrary the role of wood extractive content remains unclear. This work focuses on the fast-growing tropical species Bagassa guianensis and we report herein a correlation between heartwood drying shrinkage and extractive content. Chemical extractions and shrinkage experiments were performed on separate wood twin samples to better evaluate correctly how secondary metabolites influence the wood shrinkage behaviour. Extractive content were qualitatively and quantitatively analysed using HPLC and NMR spectroscopy. We found that B guianensis heartwood has a homogeneous low shrinkage along its radius that could not be explained only by its basic density. In fact the low drying shrinkage is correlated to the high extractive content and a corrected model to improve the prediction of wood dimensional stability is presented. Additionally NMR experiments conducted on sapwood and heartwood extracts demonstrate that secondary metabolites biosynthesis occurs in sapwood thus revealing B. guianensis as a Juglans-Type heartwood formation. This work demonstrates that B. guianensis, a fast-growing species associated with high durability and high dimensional stability, is a good candidate for lumber production and commercial purposes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0150777PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4805377PMC
July 2016

Isolation of Guttiferones from Renewable Parts of Symphonia globulifera by Centrifugal Partition Chromatography.

Planta Med 2015 Nov 21;81(17):1604-8. Epub 2015 Sep 21.

Laboratoire de Pharmacognosie, UMR CNRS 8638 COMETE (Chimie Organique, Médicinale, Extractive, Toxicologie et Environnement), Université Paris Descartes Sorbonne Paris Cité, Paris, France.

The aim of this study was to investigate the species Symphonia globulifera, a source of polycyclic polyprenylated acyl phloroglucinols such as guttiferone A, which is known to exhibit a variety of biological activities including noticeable antileishmanial properties. Our goal was the identification and the quantification of guttiferone A in different renewable parts of S. globulifera and its preparative isolation. To the best of our knowledge, there is no data concerning its mechanism of action. Consequently, it is particularly interesting to isolate it in gram quantities in order to establish structure activity relationship studies. After performing high-performance liquid chromatography profiles detecting the presence of guttiferone A and proceeding to its quantification, a centrifugal partition chromatography methodology using a two-phase solvent system of cyclohexane/ethyl acetate/methanol/water (20 :  1 :  20 : 1, v/v/v/v) was applied to each extract. In conclusion, a centrifugal partition chromatography system has been developed to ensure a fast, reliable, and scalable way to isolate, with a high level of purity, guttiferone A from five renewable parts of S. globulifera. Moreover, this methodology can be extended to the isolation of other polycyclic polyprenylated acyl phloroglucinols such as guttiferones B, C, and D.
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http://dx.doi.org/10.1055/s-0035-1557773DOI Listing
November 2015

Use of Plasmodium falciparum culture-adapted field isolates for in vitro exflagellation-blocking assay.

Malar J 2015 Jun 4;14:234. Epub 2015 Jun 4.

Laboratoire de Parasitologie, Institut Pasteur de la Guyane, Cayenne, French Guiana, France.

Background: A major requirement for malaria elimination is the development of transmission-blocking interventions. In vitro transmission-blocking bioassays currently mostly rely on the use of very few Plasmodium falciparum reference laboratory strains isolated decades ago. To fill a piece of the gap between laboratory experimental models and natural systems, the purpose of this work was to determine if culture-adapted field isolates of P. falciparum are suitable for in vitro transmission-blocking bioassays targeting functional maturity of male gametocytes: exflagellation.

Methods: Plasmodium falciparum isolates were adapted to in vitro culture before being used for in vitro gametocyte production. Maturation was assessed by microscopic observation of gametocyte morphology over time of culture and the functional viability of male gametocytes was assessed by microscopic counting of exflagellating gametocytes. Suitability for in vitro exflagellation-blocking bioassays was determined using dihydroartemisinin and methylene blue.

Results: In vitro gametocyte production was achieved using two isolates from French Guiana and two isolates from Cambodia. Functional maturity of male gametocytes was assessed by exflagellation observations and all four isolates could be used in exflagellation-blocking bioassays with adequate response to methylene blue and dihydroartemisinin.

Conclusion: This work shows that in vitro culture-adapted P. falciparum field isolates of different genetic background, from South America and Southeast Asia, can successfully be used for bioassays targeting the male gametocyte to gamete transition, exflagellation.
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http://dx.doi.org/10.1186/s12936-015-0752-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464717PMC
June 2015

Comparative LC-MS-based metabolite profiling of the ancient tropical rainforest tree Symphonia globulifera.

Phytochemistry 2014 Dec 6;108:102-8. Epub 2014 Oct 6.

Laboratoire de Pharmacognosie, UMR 8638, Université Paris Descartes Sorbonne Paris Cité, 4 Avenue de l'Observatoire, 75006 Paris, France.

In the last few years, several phytochemical studies have been undertaken on the tropical tree Symphonia globulifera leading to the isolation and characterisation of several compounds exhibiting antiparasitic activities against Plasmodium falciparum, Trypanosoma brucei and Leishmania donovani. The comparative LC-MS based metabolite profiling study conducted on the tree led to the identification of compounds originating from specific tissues. The results showed that renewable organs/tissues can be used as the starting material for the production of polycyclic poly-prenylated-acylphloroglucinols, therefore reducing impacts on biodiversity. This study also underlined the lack of knowledge on the secondary metabolites produced by S. globulifera since only a small number of the total detected features were putatively identified using the database of known compounds for the species.
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http://dx.doi.org/10.1016/j.phytochem.2014.09.009DOI Listing
December 2014

Antimicrobial and cytotoxic secondary metabolites from tropical leaf endophytes: Isolation of antibacterial agent pyrrocidine C from Lewia infectoria SNB-GTC2402.

Phytochemistry 2013 Dec 1;96:370-7. Epub 2013 Nov 1.

CNRS - Institut de Chimie des Substances Naturelles, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette cedex, France; CNRS, UMR ECOFOG, Institut Pasteur de la Guyane, 23 Avenue Pasteur, 97300 Cayenne, France; Laboratório de Farmacognosia, Universidade de Brasília, Brasília, DF, Brazil.

Because of the symbiotic nature of endophytes, this survey aims to investigate the probability of discovering antibacterial, antifungal and cytotoxic activities in leaf endophytic microbes. We isolated 138 cultivable microbes (121 fungi, 3 bacteria and 14 unidentified or unknown microbes) from 24 plant species, a significant relative proportion of which exhibited antifungal and cytotoxic potential against Candida albicans ATCC 10213 and the human cell lines KB (uterine cervical carcinoma), MDA-MB-435 (melanoma), and MRC5 (normal human lung fibroblasts). Three active fungal extracts were fractionated, resulting in the isolation of eight compounds. Seven had been described in the literature including the following: acremonisol A, semicochliodinol A, cochliodinol, griseofulvin, pyrenocin A, novae zelandin A and alterperylenol. A previously unreported compound named pyrrocidine C was isolated from Lewia infectoria SNB-GTC2402 and identified by spectroscopic analysis. As in pyrrocidines A and B, this compound is a cis-substituted decahydrofluorene with a quaternary carbon at C-5 and opposite stereochemistry at C-8 corresponding to C-6 of pyrrocidines A and B.
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http://dx.doi.org/10.1016/j.phytochem.2013.10.004DOI Listing
December 2013

Catalysis in the Service of Green Chemistry: Nobel Prize-Winning Palladium-Catalysed Cross-Couplings, Run in Water at Room Temperature: Heck, Suzuki-Miyaura and Negishi reactions carried out in the absence of organic solvents, enabled by micellar catalysis.

Platin Met Rev 2012 Apr;56(2):62-74

Department of Chemistry, University of California, Santa Barbara, CA 93106, USA.

Palladium-catalysed cross-couplings, in particular Heck, Suzuki-Miyaura and Negishi reactions developed over three decades ago, are routinely carried out in organic solvents. However, alternative media are currently of considerable interest given an increasing emphasis on making organic processes 'greener'; for example, by minimising organic waste in the form of organic solvents. Water is the obvious leading candidate in this regard. Hence, this review focuses on the application of micellar catalysis, in which a 'designer' surfactant enables these award-winning coupling reactions to be run in water at room temperature.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608409PMC
http://dx.doi.org/10.1595/147106712x629761DOI Listing
April 2012

Organozinc Chemistry Enabled by Micellar Catalysis. Palladium-Catalyzed Cross-Couplings between Alkyl and Aryl in Water at Room Temperature.

Organometallics 2011 Nov 21;30(22):6090-6097. Epub 2011 Nov 21.

Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106, United States.

Negishi-like cross-couplings between (functionalized) alkyl and aryl bromides are described. Despite the fact that organozinc reagents are intolerant of water, their formation as well as their use in an aqueous micellar environment is discussed herein. Each component of this complex series of events leading up to C-C bond formation has an important role which has been determined insofar as the type of zinc, amine ligand, surfactant, and palladium catalyst are concerned. In particular, the nature of the surfactant has been found to be crucial in order to obtain synthetically useful results involving highly reactive, moisture-sensitive organometallics. Neither organic solvent nor heat is required for these cross-couplings to occur; just add water.
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http://dx.doi.org/10.1021/om200846hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608413PMC
November 2011

TPGS-750-M: a second-generation amphiphile for metal-catalyzed cross-couplings in water at room temperature.

J Org Chem 2011 Jun 9;76(11):4379-91. Epub 2011 May 9.

Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States.

An environmentally benign surfactant (TPGS-750-M), a diester composed of racemic α-tocopherol, MPEG-750, and succinic acid, has been designed and readily prepared as an effective nanomicelle-forming species for general use in metal-catalyzed cross-coupling reactions in water. Several "name" reactions, including Heck, Suzuki-Miyaura, Sonogashira, and Negishi-like couplings, have been studied using this technology, as have aminations, C-H activations, and olefin metathesis reactions. Physical data in the form of DLS and cryo-TEM measurements suggest that particle size and shape are key elements in achieving high levels of conversion and, hence, good isolated yields of products. This new amphiphile will soon be commercially available.
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http://dx.doi.org/10.1021/jo101974uDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3608414PMC
June 2011

Stereoselective Negishi-like couplings between alkenyl and alkyl halides in water at room temperature.

Org Lett 2010 Nov;12(21):4742-4

Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106, United States.

Mix in water and then stir. That is all that is required in this new approach to stereoselective sp(3)-sp(2) cross-couplings between an alkyl and alkenyl halide. Prior formation of organozinc reagents is not required.
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http://dx.doi.org/10.1021/ol101885tDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3365513PMC
November 2010

UC Pd: a new form of Pd/C for Sonogashira couplings.

Chemistry 2010 Mar;16(11):3366-71

University of California, Santa Barbara, CA 93106, USA.

Screening of different sources of Pd/C shows reagents of highly variable nanoparticle sizes and oxidation states of the metal. Typically, catalysts with higher surface area are viewed as likely to be the more reactive. In this paper a new form of Pd/C, "UC Pd" is described that is shown to contain larger nanoparticles yet it is the most reactive catalyst of those sold commercially for Sonogashira coupling reactions. UC Pd functions efficiently in the absence of a copper co-catalyst, under very mild and "green" conditions using inexpensive 95% EtOH at 50 degrees C. It is also the only form of Pd/C that can be recycled. In side-by-side reactions with several commercially available forms of Pd/C, none compete successfully with UC Pd under standardized conditions. Physical data obtained from extensive surface analysis using TEM, XRD, XPS, and CO-TPD measurements lead to an explanation behind the unique reactivity of this new recyclable form of Pd/C.
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http://dx.doi.org/10.1002/chem.200902471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3959799PMC
March 2010

Cross-couplings between benzylic and aryl halides "on water": synthesis of diarylmethanes.

Chem Commun (Camb) 2010 Jan 9;46(4):562-4. Epub 2009 Dec 9.

Department of Chemistry & Biochemistry, University of California, Santa Barbara, CA 93106, USA.

A remarkably simple entry to unsymmetrical diarylmethanes has been developed that relies on an in situ organozinc-mediated, palladium-catalyzed cross-coupling. Thus, by mixing a benzyl and aryl halide together in the presence of Zn metal and a Pd catalyst, diarylmethanes are formed at room temperature without assistance by a surfactant; hence, "on water".
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http://dx.doi.org/10.1039/b922280dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3152455PMC
January 2010

Zn-mediated, Pd-catalyzed cross-couplings in water at room temperature without prior formation of organozinc reagents.

J Am Chem Soc 2009 Nov;131(43):15592-3

Department of Chemistry & Biochemistry, University of California, Santa Barbara, California 93106, USA.

Mix in water, stir. That is all that is required in this new approach to sp(3)-sp(2) cross-couplings between an alkyl iodide and an aryl bromide, both potentially bearing functionality. They react under catalysis by Pd(0) in the presence of zinc powder, aided by a nonionic amphiphile, to give the alkylated aromatic. No organic solvents and no heating; just add water.
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http://dx.doi.org/10.1021/ja906803tDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3359135PMC
November 2009

Manganese-catalyzed oxidative cross-coupling of Grignard reagents with oxygen as an oxidant.

Angew Chem Int Ed Engl 2009 ;48(36):6731-4

Department of Chemistry, CNRS-Université de Paris 13, 74 Rue Marcel Cachin, 93017 Bobigny, France.

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http://dx.doi.org/10.1002/anie.200902188DOI Listing
October 2009

Chemistry of organomanganese(II) compounds.

Chem Rev 2009 Mar;109(3):1434-76

Department of Chemistry, CNRS-Université de Paris13, 74 Rue Marcel Cachin, F-93017 Bobigny, France.

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http://dx.doi.org/10.1021/cr800341aDOI Listing
March 2009

A new efficient catalytic system for the chemoselective cobalt-catalyzed cross-coupling of aryl Grignard reagents with primary and secondary alkyl bromides.

Org Lett 2009 Jan;11(2):277-80

Department of Chemistry, CNRS-Universite de Paris13, 74 Rue Marcel Cachin, F-93017 Bobigny, France.

The cobalt-catalyzed alkylation of aromatic Grignard reagents is performed in good yields by using a new simple and efficient catalytic system: CoCl(2)/TMEDA (1:1). Primary and secondary cyclic or acyclic alkyl bromides were used successfully. The reaction is highly chemoselective since ester, amide, and keto groups are tolerated. The procedure is inexpensive and very easy to carry out on a larger scale.
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http://dx.doi.org/10.1021/ol802362eDOI Listing
January 2009

Manganese- or iron-catalyzed homocoupling of grignard reagents using atmospheric oxygen as an oxidant.

J Am Chem Soc 2007 Nov 18;129(45):13788-9. Epub 2007 Oct 18.

Laboratoire de Synthèse Organique Sélective et de Chimie Organométallique, UMR 8123 CNRS-ESCOM-UCP, 5 Mail Gay Lussac, Neuville s/Oise, F-95092 Cergy-Pontoise, France.

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http://dx.doi.org/10.1021/ja075417kDOI Listing
November 2007