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Nixon, S., Agwa, A., Robinson, S., Walker, A., Touchard, A., Schroeder, C., et al. (2020). Discovery and characterisation of novel peptides from Amazonian stinging ant venoms with antiparasitic activity. Toxicon, 177(1), S60.
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Nirma, C., Rodrigues, A. M. S., Basset, C., Chevolot, L., Girod, R., Moretti, C., et al. (2012). Larvicidal activity of isoflavonoids from Muellera frutescens extracts against Aedes aegypti. Natural Product Communications, 7(10), 1319–1322.
Abstract: The biological activity of extracts from the leaves, bark and roots of Muellera frutescens, an Amazonian ichtyotoxic plant, were evaluated to find new environmentally safe insecticides. The n-hexane extracts of bark, leaf, and root showed a strong toxic activity against Aedes aegypti mosquito larvae. Bioguided fractionation of the bark extract led to the isolation of seven isoflavonoids (12a-hydroxyelliptone, elliptone, (-)-variabilin, rotenone, rotenolone, tephrosin and deguelin). Rotenone and deguelin are responsible for the larvicidal activity of the plant. M. frutescens leaves contain up to 0.6%, w/w, deguelin. These results justify the traditional ichtyotoxic use of M. frutescens. The leaves contain a relatively high proportion of deguelin and, therefore, can be considered as a renewable source of this environmentally friendly insecticidal isoflavonoid.
Keywords: Aedes aegypti; French Guiana; Insecticides; Isoflavonoids; Muellera frutescens
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Nirma, C., Eparvier, V., & Stien, D. (2013). Antifungal agents from Pseudallescheria boydii SNB-CN73 isolated from a nasutitermes sp. termite. J. Nat. Prod., 76(5), 988–991.
Abstract: Defense mutualisms between social insects and microorganisms have been described in the literature. The present article describes the discovery of a Pseudallescheria boydii strain isolated from Nasutitermes sp. The microbial symbiont produces two antifungal metabolites: tyroscherin and N-methyltyroscherin, a compound not previously described in the literature. Methylation of tyroscherin has confirmed the structure of N-methyltyroscherin. Both compounds are effective antifungal agents with favorable selectivity indices for Candida albicans and Trichophyton rubrum. © 2013 The American Chemical Society and American Society of Pharmacognosy.
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Nirma, C., Eparvier, V., & Stien, D. (2015). Reactivation of antibiosis in the entomogenous fungus Chrysoporthe sp. SNB-CN74. Journal of Antibiotics, 68(9), 586–590.
Abstract: Chrysoporthe sp. SNB-CN74 was isolated from a Nasutitermes corniger nest, and its ethyl acetate extract was found to exhibit very strong antibacterial activity. Two antibacterial metabolites were isolated, (-)-R-skyrin (2) and (+)-rugulosin A (3). Eventually, the fungus lost its antibiotic potential when subcultured, and the use of yeast extract induced the re-expression of these two antibiotics. Yeast extract possibly activated a cryptic pathway by mimicking the presence of an ecological competitor. © 2015 Japan Antibiotics Research Association All rights reserved.
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Nicolini, E., Caraglio, Y., Pelissier, R., Leroy, C., & Roggy, J. C. (2003). Epicormic branches: a growth indicator for the tropical forest tree, Dicorynia guianensis Amshoff (Caesalpiniaceae). Ann. Bot., 92(1), 97–105.
Abstract: Architectural analyses of temperate tree species using a chronological approach suggest that the expression of epicormic branches is closely related to low growth rates in the axes that make up the branching system. Therefore, sole consideration of epicormic criteria may be sufficient to identify trees with low secondary growth levels or with both low primary and secondary growth levels. In a tropical tree such as Dicorynia guianensis (basralocus), where chronological studies are difficult, this relationship could be very useful as an easily accessible indicator of growth potentials. A simple method of architectural tree description was used to characterize the global structure of more than 1650 basralocus trees and to evaluate their growth level. Measurements of simple growth characters [height, basal diameter, internode length of submittal part (top of the main axis of the tree)] and the observation of four structural binary descriptors on the main stem (presence of sequential branches and young epicormic branches, state of the submittal part, global orientation), indicated that epicormic branch formation is clearly related to a decrease in length of the successive growth units of the main stem. Analysis of height vs. diameter ratios among different tree subgroups, with and without epicormic branching, suggested that trees with epicormic branches generally have a low level of secondary growth compared with primary growth. (C) 2003 Annals of Botany Company.
Keywords: Dicorynia guianensis; architecture; epicormic branch; primary growth; secondary growth; tropical forest; French Guiana; height : diameter ratio
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Nicolini, E., Beauchene, J., De La Vallee, B. L., Ruelle, J., Mangenet, T., & Heuret, P. (2012). Dating branch growth units in a tropical tree using morphological and anatomical markers: The case of Parkia velutina Benoist (Mimosoïdeae). Ann. Forest Sci., 69(5), 543–555.
Abstract: • Context In tropical areas, studies based on the retrospective analysis of tree development have focused principally on growth ring research. The interpretation of primary growth markers is overlooked although it opens perspectives to provide long time-series on tree-crown development. • Aims This study focused on Parkia velutina, an emergent tree of neotropical rain forests. Our objectives were (1) to characterize the phenological cycle of this species, and (2) to identify temporally interpretable morphological and anatomical markers. • Methods We collected dominant branches in 14 adult trees and identified growth markers that limit longitudinal and radial increments. We coupled this approach with a 2-year phenological survey of 20 trees. • Results Leaf shedding, growth unit elongation and growth ring formation define the phenological cycle. At tree scale, this cycle is synchronous and affects all axes. At population scale, trees can be desynchronized. This cycle is annual despite some slight variability. Successive growth units and growth rings are easily identifiable. • Conclusion Dating a branch by counting the number of growth units or growth rings is possible in many years with a reasonable error. Nevertheless, estimating their precise month of formation in order to study climatic influences remains difficult. © INRA/Springer-Verlag France 2012.
Keywords: Crown development; Deciduousness; Dendrochronology; French Guiana; Growth ring; Phenology; Tree architecture; Wood anatomy
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Niamke, F. B., Amusant, N., Charpentier, J. P., Chaix, G., Baissac, Y., Boutahar, N., et al. (2011). Relationships between biochemical attributes (non-structural carbohydrates and phenolics) and natural durability against fungi in dry teak wood (Tectona grandis L. f.). Ann. For. Sci., 68(1), 201–211.
Abstract: Introduction Non-structural carbohydrates and phenolic compounds are implicated in the natural durability of wood. In order to find the chemical traits of natural durability in teak wood, the radial distribution of phenolics compounds and non-structural carbohydrates were studied in trees ranked by contrasting natural durability class against Antrodia sp. Methods Non-structural carbohydrates were analyzed by spectrophotometry after enzymatic assays and phenolics compounds using HPLC. Results High concentrations of starch, sucrose, glucose, and fructose were found in the sapwood, whereas only trace amounts were found in the heartwood. In the sapwood, low concentrations of H1 (a hydroxycinnamic acid derivative) were specifically detected. Tectoquinone was also detected in the sapwood but its content increased dramatically in the heartwood. 2-(Hydroxymethyl) anthraquinone and P1, an unidentified compound, were only detected in the heartwood and at high concentrations (>3 mg equivalent 5-methoxyflavone g(-1) dry weight. Lower concentrations of 1,4-naphthoquinone, anthraquinone-2-carboxylic acid, and lapachol were also only detected in the heartwood. H1 and tectoquinone present in the sapwood could be considered as phenolic precursors of the synthesis of heartwood toxic phenolics in the heartwood. Conclusion Correlations between natural durability and chemical composition of heartwood (quinone derivatives, P1, and non-structural carbohydrates) suggest that P1, 2-(hydroxymethyl) anthraquinone and tectoquinone could be natural durability traits. Heartwood extractives,
Keywords: Tectona grandis; Teak heartwood; Phenolic compound; Non-structural carbohydrate; Natural durability
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Niamké, F. B., Amusant, N., Stien, D., Chaix, G., Lozano, Y., Kadio, A. A., et al. (2012). 4',5'-Dihydroxy-epiisocatalponol, a new naphthoquinone from Tectona grandis L. f. heartwood, and fungicidal activity. Int. Biodeterior. Biodegrad., 74, 93–98.
Abstract: A new naphthoquinone derivative was isolated from the heartwood of the teak stem. The chemical structure of this new compound, 4',5'-dihydroxy-epiisocatalponol, was determined using 1-D and 2-D nuclear magnetic resonance experiments, vibrational circular dichroism, HRMS, and optical rotation. We showed that this new naphthoquinone derivative plays a key role in the variability of decay resistance in teak wood. A high negative correlation was found between its concentration and the mass losses of the wood samples after exposure to the brown rot Antrodia sp., the fungus that is the most virulent against teak (R = -0.9; ρ < 0.0001). In-vitro bioassays allowed us to demonstrate that 4',5'-dihydroxy-epiisocatalponol acted as a fungicide against Trametes versicolor (white rot) at 58 mg ml -1 (0.22 mM). Overall, our results demonstrated that the concentration of 4',5'-dihydroxy-epiisocatalponol could be used as a new tool to evaluate teak wood durability. © 2012 Elsevier Ltd.
Keywords: 4',5'-Dihydroxy-epiisocatalponol; Decay resistance; Fungicidal; Heartwood; Naphthoquinone; Tectona grandis
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Niamké, F. B., Amusant, N., Kadio, A. A., Thevenon, M. - F., Nourissier, S., Adima, A. A., et al. (2014). Rapid prediction of phenolic compounds as chemical markers for the natural durability of teak (Tectona grandis Linn f.) heartwood by near infrared spectroscopy. J. Near Infrared Spectrosc., 22(1), 35–43.
Abstract: Near infrared (NIR) spectroscopy provides rapid and non-destructive analysis of wood properties and composition. In this study, we aimed to use NIR measurement for the prediction of teak phenolic compounds, which are chemical markers for natural durability of wood. Twenty-seven teak trees from two geographical zones (Malaysia and Ivory Coast) were used. On ground heartwood samples, the content of total phenolics and individual quinones (tectoquinone, 2-(hydroxymethyl)anthraquinone, 2-anthraquinone carboxylic acid, 1,4-naphthoquinoneand 4c,5c-dihydroxy-epiisocatalponol) were determined using high performance liquid chromatography (HPLC). Partial least squares (PLS) regression with NIR spectra on the same samples and phenolic data was used to build NIR models for phenolic contents. The PLS models for the total predicted phenolics and three quinone contents (tectoquinone, 2-(hydroxymethyl) anthraquinone, and 4¢,5¢-dihydroxy-epiisocatalponol) showed a good ratio of performance to deviation (RPD ≥ 2.5), strong coefficients of determination (r2 ≥ 0.8) and the prediction errors were consistent with the reference method. These results demonstrate that NIR spectroscopy can be reliable for the evaluation of total phenolics and individual quinones in teak heartwood wood meal. NIR spectroscopy is a promising technique for rapidly providing information on the quinone contents in teak wood and indirectly for knowing its natural durability. This finding leads to a precise, non-destructive tool for teak wood quality evaluation. © IM Publications LLP 2014.
Keywords: Heartwood; Hplc; Natural durability; NIR spectroscopy; Phenolic; Prediction; Quinone; Tectona grandis
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Nasr, H., Domenach, A. M., Ghorbel, M. H., & Benson, D. R. (2007). Divergence in symbiotic interactions between same genotypic PCR-RFLP Frankia strains and different Casuarinaceae species under natural conditions. Physiol. Plant., 130(3), 400–408.
Abstract: The symbiotic interactions between Frankia strains and their associated plants from the Casuarinaceae under controlled conditions are well documented but little is known about these interactions under natural conditions. We explored the symbiotic interactions between eight genotypically characterized Frankia strains and five Casuarinaceae species in long-term field trials. Characterization of strains was performed using the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) for the nifD-nifK intergenic transcribed spacer (ITS) and 16S-23S ITS. Assessments of the symbiotic interactions were based on nodulation patterns using nodule dry weight and viability, and on actual N-2 fixation using the delta N-15 method. The PCR-RFLP patterns showed that the analyzed strains belonged to the same genotypic group (CeD group), regardless of the host species and environment of origin. The nodule viability index is introduced as a new tool to measure the viability of perennial nodules and to predict their effectiveness. The host Casuarinaceae species was a key factor influencing both the actual N-2-fixing activity of the associated Frankia strain and the viability of nodules within a location. This is the first study providing information on the symbiotic interactions between genotypically characterized Frankia strains and actinorhizal plants under natural conditions. The results revealed a way to improve a long-term management of the Casuarinaceae symbiosis.
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