title: In vitro bactericidal activity of diterpenoids isolated from Aframomum melegueta K.Schum against strains of Escherichia coli, Listeria monocytogenes and Staphylococcus aureus.
abstract: BACKGROUND
  The ethnobotanical use of Aframomum melegueta in the treatment of urinary tract and soft tissue infection suggested that the plant has antimicrobial activity.
  
  
  METHODS
  To substantiate the folkloric claims, an acetone, 50:50 acetone:methanol and 2:1 chloroform:methanol extracts were tested against Escherichia coli K12; acetone extract and the fractions of acetone extracts were tested against Listeria monocytogenes. Bioassay-guided fractionation was performed on the extract using L. monocytogenes as the test organism to isolate the bioactive compounds which were then tested against all the other organisms.
  
  
  RESULTS
  Four known labdane diterpenes (G3 and G5) were isolated for the first time from the rhizomes of A. melegueta and purified. These were tested against E. coli, L. monocytogenes, methicillin resistant Staphylococus aureus (MRSA) and S. aureus to determine antibacterial activity. The result showed that two compounds G3 and G5 exhibited more potent antibacterial activity compared to the current clinically used antibiotics ampicillin, gentamicin and vancomycin and can be potential antibacterial lead compounds. The structure of the labdane diterpenes were elucidated using nuclear magnetic resonance (NMR) spectroscopy and Mass spectrometry. A possible mode of action of the isolated compound G3 and its potential cytotoxicity towards mammalian cells were also discussed.
  
  
  CONCLUSIONS
  The results confirmed the presence of antibacterial compounds in the rhizomes of A. melegueta with a favourable toxicity profile which could be further optimized as antibacterial lead compounds.
authors.affiliation: Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom. Electronic address: kg.ngwoke@unizik.ed.ng.
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Ngwoke
authors.affiliation: Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Olivier
authors.initials: O
authors.lastname: Chevallier
authors.affiliation: Catholic Private School of Nursing, Midwifery and Laboratory Technology, Shisong, P.O. Box 8, Kumbo, Bui Division, NW Province, Cameroon.
authors.forename: Venasius K
authors.initials: VK
authors.lastname: Wirkom
authors.affiliation: School of chemistry and Chemical Engineering, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Paul
authors.initials: P
authors.lastname: Stevenson
authors.affiliation: Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Elliott
authors.affiliation: Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom.
authors.forename: Chen
authors.initials: C
authors.lastname: Situ
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D015169:Colony Count, Microbial; D004224:Diterpenes / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D008089:Listeria monocytogenes / Q000187:drug effects / Q000254:growth & development; D013211:Staphylococcus aureus / Q000187:drug effects / Q000254:growth & development; D030521:Zingiberaceae
chemical_list: D000900:Anti-Bacterial Agents; D004224:Diterpenes
keywords: Aframomum melegueta; Antibacterial activity; Labdane diterpenes; Rhizomes