Planta Med 2014; 80 - P2B41
DOI: 10.1055/s-0034-1394918

In vitro bactericidal activity of diterpenoids isolated from Aframomum melegueta K. Schum against strains of Escherichia coli, Listeria monocytogenes and Staphylococcus aureus

K Ngwoke 1, O Chevallier 2, V Wirkom 4, P Stevenson 2, C Elliott 2, C Situ 2
  • 1Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, PMB 5025, Awka, Nigeria
  • 2Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom
  • 3School of chemistry and Chemical Engineering, Queen's University Belfast, Belfast, United Kingdom
  • 4Catholic Private School of Nursing, Midwifery and Laboratory Technology, Shisong, P.O. Box 8, Kumbo, Bui Division, NW Province, Cameroon

The ethnobotanical use of Aframomum melegueta K. Schum (Zingiberaceae) in the treatment of urinary tract and soft tissue infection suggested that the plant has antimicrobial activity. To substantiate the folkloric claims, an acetone, acetone-methanol (1:1) and chloroform-methanol (2:1) extracts were tested against E. coli K12. Acetone extract and its fractions were tested against Listeria monocytogenes. Bioassay-guided fractionation was performed to isolate the bioactive compounds using L. monocytogenes as test microorganism, and then the active compounds were tested against other microorganisms. Ampicillin, gentamicin and vancomycin were used as positive controls. Four known labdane diterpenes 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 and Staphylococcus aureus to determine antibacterial activity. Two compounds, G3 and G5, exhibited antibacterial activity and can be potential antibacterial lead compounds. The structure of the labdane diterpenes were elucidated using Nuclear Magnetic Resonance spectroscopy and Mass spectrometry. A possible mode of action of the isolated compound G3 and its potential cytotoxicity towards mammalian cells were also discussed. The results confirmed the presence of antibacterial compounds in the rhizomes of A. melegueta with a favorable toxicity profile which could be further optimized as antibacterial lead compounds.

Acknowledgements: Institute for Global Food Security, Queen's University Belfast, Belfast, United Kingdom, School of Chemistry and Chemical Engineering, Queen's University Belfast, Belfast, United Kingdom, Catholic Private School of Nursing, Midwifery and Laboratory Technology, Shisong, P. O. Box 8, Kumbo, Bui Division, NW Province, Cameroon.

Keywords: Aframomum melegueta, labdane diterpenes, antibacterial activity, rhizomes, zingiberaceae

References:

[1] Gbolade, A., 2012. Ethnobotanical study of plants used in treating hypertension in Edo State of Nigeria. J. Ethnopharmacol. 144, 1 – 10.