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Li G.,Institute of Environmental Research INFU | Kusari S.,Institute of Environmental Research INFU | Golz C.,TU Dortmund | Strohmann C.,TU Dortmund | Spiteller M.,Institute of Environmental Research INFU
RSC Advances | Year: 2016

Three new cyclic pentapeptides (1-3) and a known cyclic lipopeptide, fusaristatin A (4), were isolated from an endophytic fungus, Fusarium decemcellulare LG53, harbored in a Chinese medicinal plant Mahonia fortunei. The planar structures of the new compounds were elucidated by extensive spectroscopic analyses using HRMSn and NMR. Their absolute configurations were unambiguously determined by single crystal X-ray diffraction and Marfey's method. Interestingly, compounds 1-3 exhibited no antibacterial activity against a panel of Gram-positive and Gram-negative bacteria. In order to explore the plausible ecological relevance of the compounds within the context of microbial crosstalk and communication strategies, we designed antagonistic and dual-culture assays combined with matrix-assisted laser desorption ionization imaging high-resolution mass spectrometry (MALDI-imaging-HRMS) to investigate the interaction of F. decemcellulare LG53 with another fungal endophyte Glomerella acutata LG52 isolated from the same tissue of the plant. Compound 4 was found to display an allelopathic effect on endophytic G. acutata LG52. Our results provide a proof-of-concept of balanced antagonism that might be occurring between endophytes inhabiting the same plant tissues in distinct ecological niches. © 2016 The Royal Society of Chemistry.


Happi G.M.,University of Yaounde I | Happi G.M.,Institute of Environmental Research INFU | Kouam S.F.,University of Yaounde I | Talontsi F.M.,Institute of Environmental Research INFU | And 5 more authors.
Journal of Natural Products | Year: 2015

Eight new triterpenoids, prototiamins A-G (1-6, 9) and seco-tiaminic acid A (10), were isolated along with four known compounds from the bark of Entandrophragma congoënse. Their structures were elucidated by means of HRMS and different NMR techniques and chemical transformations. Assignments of relative and absolute configurations for the new compounds were achieved using NOESY experiments and by chemical modification including the advanced Mosher's method. Additionally, the structure and relative configuration of compound 3 were confirmed by single-crystal X-ray diffraction analysis. Compounds 1, 3, and 5 displayed significant in vitro antiplasmodial activity against the erythrocytic stages of chloroquine-sensitive Plasmodium falciparum strain NF54. Prototiamin C (3) was the most potent of the compounds isolated, with an IC50 value of 0.44 μM. All compounds tested showed low cytotoxicity for the L6 rat skeletal myoblast cell line. © 2015 American Chemical Society and American Society of Pharmacognosy.


Kusari S.,Institute of Environmental Research INFU | Pandey S.P.,Indian Institute of Science | Spiteller M.,Institute of Environmental Research INFU
Phytochemistry | Year: 2013

The biosynthetic potential of endophytic fungi has gained impetus in recent times owing to the continual discovery of fungal endophytes capable of synthesizing plant compounds. However, the sustained production of the desired plant compounds has not yet been achieved using endophytes. It is thus imperative to investigate the diverse interactions that endophytes have with coexisting endophytes, host plants, insect pests, and other specific herbivores. The precise role of these associations on the endophytic production of host plant compounds is mostly overlooked and open to future discoveries. Here, highlighted are the implications of the poorly investigated links and molecular mechanisms that might trigger similar chemical responses in both plants and endophytes. Elucidating such connections can not only enhance the understanding of evolution of complex defense mechanisms in plants and associated organisms, but also help in the sustained production of plant compounds using endophytes harbored within them. © 2012 Elsevier Ltd. All rights reserved.


Chenda L.B.N.,P.A. College | Chenda L.B.N.,Institute of Environmental Research INFU | Kouam S.F.,P.A. College | Lamshoft M.,Institute of Environmental Research INFU | And 4 more authors.
Phytochemistry | Year: 2014

Six labdane diterpene derivatives, named turraeanins F-J (3-6, 8) and epi-turraeanin J (7), and a pregnane steroid derivative named turraeasterodionene (2), were isolated by preparative high performance liquid chromatography together with thirteen known compounds from the Cameroonian medicinal plant Turraeanthus africanus. Their structures were elucidated by means of nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry in conjunction with the published data for the analogs, as well as the fragmentation patterns of each compound. Most of the known compounds were obtained for the first time from this plant. The compounds (2-7) were tested for their antibacterial efficacies against both Gram-positive and Gram-negative bacteria, including some clinically-important Risk group 2 human pathogens. Compound 4 exhibited the most pronounced antibacterial effectiveness comparable to standard reference streptomycin, with more potency against Gram-positive than Gram-negative bacteria. By comparing compounds 3, 4 and 5, a tentative structure-activity relationship could be drawn; selected oxidations at C-16 and C-18 drastically reduced the antibacterial efficacy of the parent compound (4). These results revealed the potential of compound 4 as a suitable antibacterial lead compound that might be used for further development of other derivatives to increase the antimicrobial efficacy. © 2014 Elsevier Ltd. All rights reserved.


Kouam S.F.,Institute of Environmental Research INFU | Kouam S.F.,University of Yaounde I | Kusari S.,Institute of Environmental Research INFU | Lamshoft M.,Institute of Environmental Research INFU | And 2 more authors.
Phytochemistry | Year: 2012

Four acyclic triterpene derivatives named sapelenins G-J (1-4), along with eight known compounds, sapelenins A-D, ekeberin D2 (5), (+)-catechin and epicatechin, and anderolide G, were isolated from the stem bark of the Cameroonian medicinal plant, Entandrophragma cylindricum Sprague, on the basis of bioassay-guided fractionation. Their structures were determined by means of high-resolution mass spectrometry and NMR spectroscopic data, as well as by comparison with the literature values of their analogs. The absolute configurations of the compounds (1-4) were assigned by the modified Mosher's method in conjunction with NOESY experiments and chemical modifications. The anti-inflammatory activities of the sapelenins were evaluated by assessing their ability to suppress or inhibit the secretion of cytokine interleukin-17 (IL-17) by human peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin (PHA). The cytotoxicity of these compounds on PMBCs was further assessed for correctly interpreting their anti-inflammatory responses. The tested compounds demonstrated moderate to significant anti-inflammatory activities by suppressing the secretion of IL-17 by PHA-stimulated human PBMCs. One of them, sapelenin G (1), showed high potency in suppressing the secretion of IL-17 by PBMCs comparable to reference cyclosporine A, without causing any cytotoxic effects (negligible), and deserves further considerations towards developing an effective anti-inflammatory drug. © 2012 Elsevier Ltd. All rights reserved.


Happi G.M.,University of Yaounde I | Happi G.M.,Institute of Environmental Research INFU | Kouam S.F.,University of Yaounde I | Talontsi F.M.,Institute of Environmental Research INFU | And 3 more authors.
Fitoterapia | Year: 2015

Two new tirucallane-type triterpenoids were isolated from the bark of Entandrophragma congoënse (Meliaceae) along with five known compounds gladoral A, bipendensin, 4-hydroxymethyl-3,5-dimethyldihydrofuran-2(3H)-one, scopoletin and 5,7-dimethoxy-6-hydroxycoumarin. Their structures were elucidated by means of spectroscopic analyses including 1D and 2D-NMR spectroscopy, high resolution mass spectrometric data as well as the comparison of data with those reported in the literature. The tested compounds (1-4) displayed moderated antiplasmodial activity against erythrocytic stages of chloroquine-resistant Plasmodium falciparum strain NF54 and low cytotoxicity on L6 cell lines. All the isolated compounds are reported for the first time from the genus Entandrophragma. © 2015 Elsevier B.V. All rights reserved.

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