Synergistic antimicrobial activity of galangal (Alpinia galanga), rosemary (Rosmarinus officinalis) and lemon iron bark (Eucalyptus staigerana) extracts

BACKGROUND: In this study the synergistic antimicrobial activities of combinations of extracts from galangal (Alpinia galanga), rosemary (Rosmarinus officinalis) and lemon iron bark (Eucalyptus staigerana) were evaluated against Staphylococcus aureus, Listeria monocyto genes, Escherichia coil, Salmonella typhimurium and Clostridium perfringens. Chemical compositions of these extracts were also,determined to provide further insight into antimicrobial constituents and their potential mechanisms of action. RESULTS: Combinations of galangal with either rosemary or lemon iron bark showed synergistic antimicrobial activity. Specifically, galangal and rosemary showed synergistic activity against S. aureus and L. monocytogenes only, while galangal and lemon iron bark showed synergistic activity against E. coil and S. typhimurium. Chemical compositions of the extracts were determined by gas chromatographic-mass spectrometric analysis. The major chemical components of the galangal and lemon iron bark extracts were 1 -acetoxy-chavicol acetate (1 ACA) (63.4 ) and neral (15.6 ), respectively, while 1,8-cineole (26.3 ) and camphor (20.3 ) were identified as major chemical components of the rosemary extract. CONCLUSION: The results of this study show that galangal, rosemary and lemon iron bark extracts contain components that may have different modes of antimicrobial action and combinations of these extracts may have potential as natural antimicrobials to preserve foods.