title: Antibacterial and antibiotic-resistance modifying activity of the extracts and compounds from Nauclea pobeguinii against Gram-negative multi-drug resistant phenotypes.
abstract: BACKGROUND
  Multi-drug resistance of Gram-negative bacteria constitutes a major obstacle in the antibacterial fight worldwide. The discovery of new and effective antimicrobials and/or resistance modulators is necessary to combat the spread of resistance or to reverse the multi-drug resistance. In this study, we investigated the antibacterial and antibiotic-resistance modifying activities against 29 Gram-negative bacteria including multi-drug resistant (MDR) phenotypes of the methanol extracts from Nauclea pobeguiinii leaves (NPL), Nauclea pobeguiinii bark (NPB) and six compounds from the bark extract, identified as 3-acetoxy-11-oxo-urs-12-ene (1), p-coumaric acid (2), citric acid trimethyl ester (3), resveratrol (4), resveratrol β- D -glucopyranoside (5) and strictosamide (6).
  
  
  METHODS
  The broth microdilution method was used to determine the minimal inhibitory concentrations (MIC) and minimal bactericidal concentrations (MBC) of crude extracts and compounds as well as the antibiotic-resistance modifying effects of MPB and 4.
  
  
  RESULTS
  MIC determinations indicate values ranging from 32-1024 μg/mL for NPB and NPL on 89.7 % and 69.0 % of the tested bacterial strains respectively. MIC values below 100 μg/mL were obtained with NPB against Escherichia coli ATCC10536, AG100 and Enterobacter aerogenes CM64 strains. The lowest MIC value for crude extracts of 32 μg/mL was obtained with NPB against E. coli ATCC10536. Compound 4 was active all tested bacteria, whilst 1, 3 and 6 displayed weak and selective inhibitory effects. The corresponding MIC value (16 μg/mL) was obtained with 4 against Klebsiella pneumoniae KP55 strain. Synergistic effects of the combination of NPB with chloramphenicol (CHL), kanamycin (KAN) as well as that of compound 4 with streptomycin (STR) and ciprofloxacin (CIP) were observed.
  
  
  CONCLUSIONS
  The present study provides information on the possible use of Nauclea pobeguinii and compound 4 in the control of Gram-negative bacterial infections including MDR phenotypes. It also indicates that NPB and 4 can be used as naturally occurring antibiotic-resistance modulators to tackle MDR bacteria.
authors.affiliation: Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon.
authors.forename: Jackson A
authors.initials: JA
authors.lastname: Seukep
authors.affiliation: Department of Pharmaceutical Sciences, CCS, Federal University of Santa Catarina, Florianópolis, 88040-900, SC, Brazil.
authors.forename: Louis P
authors.initials: LP
authors.lastname: Sandjo
authors.affiliation: Department of Organic Chemistry, Faculty of Science, University of Yaoundé 1, Yaoundé, Cameroon.
authors.forename: Bonaventure T
authors.initials: BT
authors.lastname: Ngadjui
authors.affiliation: Department of Biochemistry, Faculty of Science, University of Dschang, Dschang, Cameroon. kuetevictor@yahoo.fr.
authors.forename: Victor
authors.initials: V
authors.lastname: Kuete
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D000077185:Resveratrol; D019666:Rubiaceae / Q000737:chemistry*; D013267:Stilbenes / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D010936:Plant Extracts; D013267:Stilbenes; D000077185:Resveratrol
keywords: Antibacterial; Efflux pumps; Gram-negative bacteria; Multidrug resistant; Nauclea pobeguinii; Resveratrol