72 research outputs found
Endiandric acid derivatives from the stem bark of Beilschmiedia anacardioides
No full textChouna JR, Nkeng-Efouet PA, Lenta BN, Wansi JD, Kimbu SF, Sewald N. Endiandric acid derivatives from the stem bark of Beilschmiedia anacardioides. Phytochemistry Letters. 2010;3(1):13-16.Three new endiandric acid derivatives, beilschmiedic acids D, E and beilschmiedin were isolated from the stem bark of Beilschmiedia anacardioides together with the known compounds bisabolene and tricosanoic acid. Their structures were determined on the basis of spectroscopic analysis. (C) 2009 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved
Endiandric Acid Derivatives and Other Constituents of Plants from the Genera Beilschmiedia and Endiandra (Lauraceae)
No full textLenta Ndjakou B, Chouna JR, Nkeng-Efouet PA, Sewald N. Endiandric Acid Derivatives and Other Constituents of Plants from the Genera Beilschmiedia and Endiandra (Lauraceae). Biomolecules . 2015;5(2):910-942.Plants of the Lauraceae family are widely used in traditional medicine and are sources of various classes of secondary metabolites. Two genera of this family, Beilschmiedia and Endiandra, have been the subject of numerous investigations over the past decades because of their application in traditional medicine. They are the only source of bioactive endiandric acid derivatives. Noteworthy is that their biosynthesis contains two consecutive non-enzymatic electrocyclic reactions. Several interesting biological activities for this specific class of secondary metabolites and other constituents of the two genera have been reported, including antimicrobial, enzymes inhibitory and cytotoxic properties. This review compiles information on the structures of the compounds described between January 1960 and March 2015, their biological activities and information on endiandric acid biosynthesis, with 104 references being cited
Obscurine: a New Cyclostachine Acid Derivative from Beilschmiedia obscura
No full textLenta BN, Chouna JR, Nkeng-Efouet PA, Kimbu SF, Tsamo E, Sewald N. Obscurine: a New Cyclostachine Acid Derivative from Beilschmiedia obscura. Natural Product Communications. 2011;6(11):1591-1592.From the methylene chloride extract of the stem bark of Bedschmiedia obscura, a new cyclostachine derivative, obscurine (1), has been isolated, together with six known compounds. The structure of compound 1 was established by spectroscopic methods, including 1- and 2-dimensional NMR techniques
Furan derivatives from Lannea kerstingii
No full textTameko JEM, Chouna JR, Nkeng-Efouet-Alango P, Tapondjou LA, Sewald N. Furan derivatives from Lannea kerstingii. Phytochemistry Letters. 2017;20:282-284.Two new furan derivatives, lannefuran A (1) and lannefuran B (2) were isolated from the stem bark extract of Lannea kerstingii Engl. & K. Krause together with five known compounds, namely: taraxerol, stigmast-4-en-3-one, monoglyceride of hexacosanoic acid, beta-sitosterol and its glucoside. Their structures were determined by means of 1D and 2D NMR, IR, and HR-EI-MS spectra and comparison with the data of known analogues reported in the literature. Lannefuran A (1) exhibited very low antiplasmodial activity against Plasmodium falciparum 3D7
Antibacterial secotirucallane triterpenes from the stem bark of Pseudocedrela kotschyi
No full textMambou CS, Nono RN, Chouna JR, Tamokou J-de-D, Nkeng-Efouet-Alango P, Sewald N. Antibacterial secotirucallane triterpenes from the stem bark of Pseudocedrela kotschyi. Zeitschrift für Naturforschung C. 2018;73(5-6):241-246.The antibacterial-guided investigation of the stem bark extract of Pseudocedrela kotschyi led to the isolation of a new secotirucallane triterpene derivative: 4-hydroxy-3,4-secotirucalla-7,24-dien-3,21-dioic acid (1), together with the known one: 3,4-secotirucalla-4(28),7,24-trien-3,21-dioic acid (2) and 3-methyl ester 3,4-secotirucalla-4(28),7,24-trien-3,21-dioic (3). The structures of the isolated compounds were elucidated on the basis of extensive 1D- and 2D-NMR spectroscopy. Extracts, fractions and compounds (1-3) were tested in vitro for antibacterial activity against two Gram positive bacteria (Bacillus subtilis and Staphylococcus aureus ATCC 25923), and two Gram negative bacteria (Escherichia coli S2(1) and Pseudomonas aeruginosa). The MeOH extract and the Hex/CH2Cl2 (70:30) fraction showed significant levels of activity (MIC = 64-256 mu g/mL) compared with the two reference drugs [ciprofloxacin: MIC (0.5-1 mu g/mL) and amoxicillin: MIC (1-128 mu g/mL)]. Moreover, the compound 2 isolated from this Hex/CH2Cl2 (70:30) fraction had the greatest potential value against S. aureus, E. coli and P. aeruginosa, with minimum inhibitory concentrations (MIC) ranging from 4-16 mu g/mL
Antimicrobial triterpenes from the stem bark of crossopteryx febrifuga
No full textChouna JR, Tamokou J-de-D, Nkeng-Efouet-Alango P, Lenta BN, Sewald N. Antimicrobial triterpenes from the stem bark of crossopteryx febrifuga. Zeitschrift für Naturforschung C. 2015;70(7-8):169-173.Phytochemical investigation of the stem bark extract of Crossopteryx febrifuga resulted in the isolation of epimeric mixtures of 3 beta-urs-12,20(30)-diene-27,28-dioic acid and 18-epi-3 beta-urs-12,20(30)-diene-27,28-dioic acid (1), as well as: 3 beta-D-glucopyranosylurs-12,20(30)-diene-27,28-dioic acid and 18-epi-3 beta-D-glucopyranosylurs-12,20(30)-diene- 27,28-dioic acid (2), together with some known compounds such as the monoglyceride of palmitic acid, as well as beta-sitosterol and its glucoside. The structures of the isolated compounds were determined by application of spectroscopic methods. The MeOH extract and compounds 1 and 2 were examined for antimicrobial activity in in vitro assays against bacteria (Enterobacter aerogenes ATCC13048, Escherichia coli ATCC8739, Klebsiella pneumoniae ATCC11296, Staphylococcus aureus) and fungi (Candida parapsilosis, Candida albicans ATCC 9002 and Cryptococcus neoformans IP 90526). The tested samples showed selective activities. The antibacterial and antifungal activities of compound 2 (MIC = 8-64 mu g/mL) were in some cases equal to or even higher than those of the respective reference drugs chloramphenicol (MIC = 16-64 mu g/mL) and nystatin (MIC = 128-256 mu g/mL)
Beilschmiedic Acids F and G, Further Endiandric Acid Derivatives from Beilschmiedia anacardioides
No full textChouna JR, Nkeng-Efouet PA, Lenta BN, et al. Beilschmiedic Acids F and G, Further Endiandric Acid Derivatives from Beilschmiedia anacardioides. Helvetica Chimica Acta. 2011;94(6):1071-1076.Two new endiandric acid derivatives, beilschmiedic acid F (1) and beilschmiedic acid G (2), together with three known constituents, beilschmiedic acid A, beilschmiedic acid C, and sitosterol 3-beta-D-glucopyranoside, were isolated from the stem bark of Beilschmiedia anacardioides. Their structures were elucidated mainly by using a combination of 1D- and 2D-NMR techniques. The structure and relative configuration of beilschmiedic acid G (2) was also confirmed by X-ray crystallographic analysis
Antibacterial endiandric acid, derivatives from Beilschmiedia anacardioides
No full textChouna JR, Nkeng-Efouet PA, Lenta BN, et al. Antibacterial endiandric acid, derivatives from Beilschmiedia anacardioides. Phytochemistry. 2009;70(5):684-688.Three endiandric acid derivatives, beilschmiedic acids A, B and C were isolated from the stem bark of Beilschmiedia anacardioides together with the known beta-sitosterol. Their structures were established by means of modern spectroscopic techniques. The relative configuration of compound 1 was determined by single crystal X-ray analysis. The antibacterial activities of compounds A,B,C were evaluated in vitro against five strains of microbes. Compound C showed strong activity against Bacillus subtilis, Micrococcus luteus and Streptococcus faecalis (MICs below 23 mu M). This Compound was more active than the reference antibiotic ampicillin against B. subtilis and M. luteus. (C) 2009 Elsevier Ltd. All rights reserved
Endiandric Acid Derivatives and Other Constituents of Plants from the Genera Beilschmiedia and Endiandra (Lauraceae)
No full textPlants of the Lauraceae family are widely used in traditional medicine and are sources of various classes of secondary metabolites. Two genera of this family, Beilschmiedia and Endiandra, have been the subject of numerous investigations over the past decades because of their application in traditional medicine. They are the only source of bioactive endiandric acid derivatives. Noteworthy is that their biosynthesis contains two consecutive non-enzymatic electrocyclic reactions. Several interesting biological activities for this specific class of secondary metabolites and other constituents of the two genera have been reported, including antimicrobial, enzymes inhibitory and cytotoxic properties. This review compiles information on the structures of the compounds described between January 1960 and March 2015, their biological activities and information on endiandric acid biosynthesis, with 104 references being cited
On the Geopolitics of Land Colonization: Order and Disorder on the Frontiers of Vietnam and Indonesia
No full textThe author wishes to thank Jean-Philippe Leblond, Bruno Thibert and Pham Thanh Hai, as well as the Social Science and Humanities Research Council of Canada, for its support to the project entitled “The Challenges of the Agrarian Transition in Southeast Asia”. “The state is panoptic. It likes to see those that it likes and even more those who do not like him. The state likes to mark out the land and regroup people.”(Translated from Brunet 1990: 63.) A Question of Territory Geopolitics Although..
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