Antimicrobial properties and action of galangal (Alpinia galanga Linn.) on Staphylococcus aureus

The ethanol extracts of the Zingiberaceae family (galangal, ginger, turmeric and krachai) were evaluated for antimicrobial action on Staphylococcus aureus 209P and Escherichia coli NIHJ JC-2 by using an agar disc diffusion assay. The galangal extract had the strongest inhibitory effect against S. aureus. The minimum inhibitory concentration (MIC) of the galangal extract was 0.325 mg/ml and the minimum bactericidal concentration (MBC) at 1.3 mg/ml using the broth dilution method. Transmission electron microscopy clearly demonstrated that the galangal extract caused both outer and inner membrane damage, and cytoplasm coagulation. The disruption of the cytoplasmic membrane properties was determined by the releasing of cell materials including nucleic acid which absorbed UV/VIS spectrophotometer at 260 nm. The major compound of the extract was d,l-1′-acetoxychavicol acetate which was identified by GC-MS and NMR.