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Basset, C., Rodrigues, A. M. S., Eparvier, V., Silva, M. R. R., Lopes, N. P., Sabatier, D., et al. (2012). Secondary metabolites from Spirotropis longifolia (DC) Baill and their antifungal activity against human pathogenic fungi. Phytochemistry, 74, 166–172.
Abstract: A phytochemical study of the ethyl acetate extract of the roots and adventitious roots of Spirotropis longifolia, a monodominant tree species of the Guianan rainforest, has allowed the isolation of three compounds: 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethylpyrano-[5′, 6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin A), 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethyl-3′, 4′-dihydropyrano-[5′,6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin B), and 5,7-dihydroxy-6,8-diprenyl-2,2-dimethylpyrano[5,6: 3′,4′]-isoflavone (spirotropone). In addition, 10 known compounds, trans-oxyresveratrol, trans-resveratrol, piceatannol, daidzein, genistein, isoprunetin, lupeol, latifolol, gnetin D and gnetin E, were also isolated. These compounds were evaluated for their antifungal activity and their cytotoxicity, and their structures were established by 1D and 2D NMR, HRMS, CD and optical rotation measurements. © 2011 Elsevier Ltd. All rights reserved.
Keywords: Antifungal; Cytotoxic; Leguminosae; Monodominant species; Prenylated pterocarpans; Spirotropis longifolia
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Cachet, N., Ho-A-Kwie, F., Rivaud, M., Houel, E., Deharo, E., Bourdy, G., et al. (2012). Picrasin K, a new quassinoid from Quassia amara L. (Simaroubaceae). Phytochem. Lett., 5(1), 162–164.
Abstract: A new quassinoid Picrasin K 1 was isolated from a decoction made of Quassia amara leaves, traditionally used in French Guyana to treat malaria. The structure and relative stereochemistry of 1 was determined through extensive NMR analysis. Picrasin K showed a low activity against Plasmodium falciparum in vitro (IC 50 = 8 μM), and a similar low activity on human cancerous cells line (IC 50 = 7 μM on MCF-7 cells line). © 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.
Keywords: Malaria; P. falciparum; Quassia amara; Quassinoids; Simaroubaceae
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Tahiri, A., Amissa Adima, A., Adjé, F. A., & Amusant, N. (2011). Pesticide effects and screening of extracts of Azadirachta Indica (A.) Juss. on the Macrotermes bellicosus rambur termite. Effet pesticide et screening des extraits de Azadirachta indica (A.) Juss. sur le termite Macroterme, 65(310), 79–88.
Abstract: To recommend applications in the field of a naturally insecticide plant substance as an alternative to chemical control against termite attacks, several important prerequisites need to be satisfied to ensure its effectiveness. The toxicity, lethal dose, mode of action, persistence of insecticide effect and chemical composition of total aqueous, alcohol and hexane extracts of the leaves and seeds of the neem tree, Azadirachta indica, were tested with the Macrotermes bellicosus termite. The extracts were found to be highly toxic to termites on contact, killing the entire population tested. The insecticide effect of the extracts persisted from 2.4 to 4.2 days. The aqueous and hexane extracts were the most toxic (LD50 0.422±0.018 to 4,466±0,162 mg/l). Contact and inhalation were both essential to their effectiveness. The aqueous extract of seeds, which is the most active, is also capable of being transferred through the colony during social tasks. However, it seems to have an anti-appetent effect on termites and does not act by ingestion. It contains phenol compounds (tannins and flavonoids) and saponins. The hexane extract of seeds is oily and contains 11 fatty acids as well as terpenoids, flavonoids and saponins.
Keywords: Azadirachta indica; Pesticide properties; Phytochemical screening; Termite
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Revel, N., Alvarez, N., Gibernau, M., & Espíndola, A. (2012). Investigating the relationship between pollination strategies and the size-advantage model in zoophilous plants using the reproductive biology of Arum cylindraceum and other European Arum species as case studies. Arthropod-Plant Interact., 6(1), 35–44.
Abstract: The size-advantage model (SAM) explains the temporal variation of energetic investment on reproductive structures (i. e. male and female gametes and reproductive organs) in long-lived hermaphroditic plants and animals. It proposes that an increase in the resources available to an organism induces a higher relative investment on the most energetically costly sexual structures. In plants, pollination interactions are known to play an important role in the evolution of floral features. Because the SAM directly concerns flower characters, pollinators are expected to have a strong influence on the application of the model. This hypothesis, however, has never been tested. Here, we investigate whether the identity and diversity of pollinators can be used as a proxy to predict the application of the SAM in exclusive zoophilous plants. We present a new approach to unravel the dynamics of the model and test it on several widespread Arum (Araceae) species. By identifying the species composition, abundance and spatial variation of arthropods trapped in inflorescences, we show that some species (i. e. A. cylindraceum and A. italicum) display a generalist reproductive strategy, relying on the exploitation of a low number of dipterans, in contrast to the pattern seen in the specialist A. maculatum (pollinated specifically by two fly species only). Based on the model presented here, the application of the SAM is predicted for the first two and not expected in the latter species, those predictions being further confirmed by allometric measures. We here demonstrate that while an increase in the female zone occurs in larger inflorescences of generalist species, this does not happen in species demonstrating specific pollinators. This is the first time that this theory is both proposed and empirically tested in zoophilous plants. Its overall biological importance is discussed through its application in other non-Arum systems. © 2011 Springer Science+Business Media B.V.
Keywords: Araceae; Flower evolution; Plant-insect interactions; Reproductive strategy; Sex allocation
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Schimann, H., Petit-Jean, C., Guitet, S., Reis, T., Domenach, A. M., & Roggy, J. - C. (2012). Microbial bioindicators of soil functioning after disturbance: The case of gold mining in tropical rainforests of French Guiana. Ecol. Indic., 20, 34–41.
Abstract: In the context of an ongoing monitoring study on the impacts of gold-mining activities on critical ecosystem processes, we explored the use of soil Denitrifying Enzyme Activity (DEA) and Substrate Induced Respiration (SIR) as ecosystem indicators in tropical rainforests of French Guiana. We also propose DEA/SIR ratio as ecosystem attribute able to describe the state of an ecosystem and to reflect changes in ecological processes. With this purpose, we measured SIR, DEA and DEA/SIR ratio in five gold-mining areas and five surrounding natural reference rainforests. We also measured indicators in two conditions of spontaneous regeneration of vegetation (stratified or not) and two conditions of soil rehabilitation (prior preparation of soils or not). We showed a high variability of DEA, SIR and DEA/SIR ratio in the natural reference forests. This pointed out the necessity to identify relevant reference systems – i.e. proving a close match in all relevant ecological dimensions – to compare with closed perturbed systems in order to assess the levels of alterations after disturbances. Results showed a high impact of gold mine on microbial processes with a strong decrease of DEA (10-fold lower), SIR (2-fold lower) and DEA/SIR ratio (8-fold lower) in perturbed areas in comparison with natural reference forests. The type of spontaneous vegetation (stratified or not) influenced the values of indicators as well as prior rehabilitation of soils, demonstrating the capacity of DEA, SIR and DEA/SIR ratio to respond in proportion to the perturbation (robustness) and to the different levels of restoration (sensitivity). The systematic decrease of the ratio DEA/SIR observed in the studied perturbed situations demonstrates clearly that the structure of microbial communities has been also modified. The ratio DEA/SIR proved to be robust and sensitive, and able to describe in fairly fine way changes of soil microbial communities in terms of structure and function in gold mine areas and during processes of restoration. We propose to use DEA, SIR and DEA/SIR ratio as bioindicators of both structural and functional aspects of C and N cycling in soils. Together with others bioindicators based on key supporting functions in soils, these indicators should accurately evaluate the ecological potential of natural ecosystems and the levels of degradation in case of land-use changes. © 2012 Elsevier Ltd.
Keywords: Bioindicators; DEA/SIR ratio; Denitrifying Enzyme Activity (DEA); Disturbance; Substrate Induced Respiration (SIR); Tropical rainforest
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Royer, M., Rodrigues, A. M. S., Herbette, G., Beauchene, J., Chevalier, M., Herault, B., et al. (2012). Efficacy of Bagassa guianensis Aubl. extract against wood decay and human pathogenic fungi. Int. Biodeterior. Biodegrad., 70, 55–59.
Abstract: Extractives that provide natural resistance to Bagassa guianensis Aubl. heartwood were examined. Soil-bed tests showed that the B. guianensis heartwood resistance was significantly reduced after ethyl acetate extraction, whereas methanol and especially water extractions improved the resistance. The ethyl acetate extract was submitted to a bioguided fractionation, and fractions were tested against one wood-destroying fungal strain (Pycnoporus sanguineus) and two human pathogenic fungal strains (Candida glabrata (yeast) and Trichophyton rubrum (filamentous dermatophyte)). Fraction F7, which exhibited the strongest antifungal activity, was subsequently fractionated by high performance liquid chromatography (HPLC). Six previously described compounds were isolated. Although the two moracins, 6-O-methyl-moracin N (3) and moracin N (4) were the most active against fungal strains with MIC values between 4 and 16 μg ml -1, the isolated compounds showed less or equivalent antifungal activity than the initial fraction. Possible synergism between compounds 3 and 4 and other secondary metabolites have been hypothesized. Our study demonstrated that this extract as a whole might be used as a wood preservation or antimycotic product. © 2012 Elsevier Ltd.
Keywords: Antifungal; Bagassa guianensis; Extractives; Natural durability; Polyphenols; Synergy
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Seipke, R. F., Barke, J., Ruiz-Gonzalez, M. X., Orivel, J., Yu, D. W., & Hutchings, M. I. (2012). Fungus-growing Allomerus ants are associated with antibiotic-producing actinobacteria. Antonie Van Leeuwenhoek Int. J. Gen. Mol. Microbiol., 101(2), 443–447.
Abstract: Fungus-growing attine ants use natural-product antibiotics produced by mutualist actinobacteria as 'weedkillers' in their fungal gardens. Here we report for the first time that fungus-growing Allomerus ants, which lie outside the tribe Attini, are associated with antifungal-producing actinobacteria, which offer them protection against non-cultivar fungi isolated from their ant-plants. © 2011 Springer Science+Business Media B.V.
Keywords: Allomerus ants; Amycolatopsis; Ant-bacteria symbioses; Fungus-growing ants; Insect fungiculture; Streptomyces
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Brouard, O., Céréghino, R., Corbara, B., Leroy, C., Pelozuelo, L., Dejean, A., et al. (2012). Understorey environments influence functional diversity in tank-bromeliad ecosystems. Freshw. Biol., 57(4), 815–823.
Abstract: A substantial fraction of the freshwater available in neotropical forests is impounded within the rosettes of bromeliads that form aquatic islands in a terrestrial matrix. The ecosystem functioning of bromeliads is known to be influenced by the composition of the contained community but it is not clear whether bromeliad food webs remain functionally similar against a background of variation in the understorey environment. We considered a broad range of environmental conditions, including incident light and incoming litter, and quantified the distribution of a very wide range of freshwater organisms (from viruses to macroinvertebrates) to determine the factors that influence the functional structure of bromeliad food webs in samples taken from 171 tank-bromeliads. We observed a gradient of detritus-based to algal-based food webs from the understorey to the overstorey. Algae, rotifers and collector and predatory invertebrates dominated bromeliad food webs in exposed areas, whereas filter-feeding insects had their highest densities in shaded forest areas. Viruses, bacteria and fungi showed no clear density patterns. Detritus decomposition is mainly due to microbial activity in understorey bromeliads where filter feeders are the main consumers of microbial and particulate organic matter (POM). Algal biomass may exceed bacterial biomass in sun-exposed bromeliads where amounts of detritus were lower but functional diversity was highest. Our results provide evidence that tank-bromeliads, which grow in a broad range of ecological conditions, promote aquatic food web diversity in neotropical forests. Moreover, although bromeliad ecosystems have been categorised as detritus-based systems in the literature, we show that algal production can support a non-detrital food web in these systems. © 2012 Blackwell Publishing Ltd.
Keywords: Food webs; French Guiana; Invertebrates; Microorganisms; Phytotelmata; Rainforest
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Vantaux, A., Roux, O., Magro, A., & Orivel, J. (2012). Evolutionary perspectives on myrmecophily in ladybirds. Psyche, 591570, 1–7.
Abstract: Myrmecophiles are species that usually have developed specialized traits to cope with the aggressiveness of ants enabling them to live in their vicinity. Many coccinellid species are predators of Hemiptera; the latter is also often protected by ants. Therefore these ladybirds frequently interact with ants, and some species have become myrmecophilous. In this paper, we aim to provide an overview of the evolution of myrmecophilous traits in ladybirds. We then discuss the costs and benefits of myrmecophily and the dietary shift to myrmecophagy observed in a few species. Copyright © 2012 Amélie Vantaux et al.
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Lacau, S., Groc, S., Dejean, A., Oliveira, M. L. D., & Delabie, J. H. C. (2012). Tatuidris kapasi sp. nov.: A new armadillo ant from French Guiana (Formicidae: Agroecomyrmecinae). Psyche, 926089, 1–6.
Abstract: Tatuidris kapasi sp. nov. (Formicidae: Agroecomyrmecinae), the second known species of “armadillo ant”, is described after a remarkable specimen collected in French Guiana. This species can be easily distinguished from Tatuidris tatusia by characters related to the shape of the mesosoma and petiole as well as to the pilosity, the sculpture, and the color. Copyright © 2012 Sébastien Lacau et al.
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