Chemical Constituents, Antibacterial Activity and Mode of Action of Elephant Ginger (Zingiber officinale var. officinale) and Emprit Ginger Rhizome (Zingiber officinale var. amarum) Essential Oils

Introduction: Ginger (Zingiber officinale Rosc) is a spice plant, which is extensively used worldwide, and morphologically classified into three types, including the red, “gajah” or “elephant”, and “emprit” ginger (common name in Indonesia). In addition, the extract and essential oils possess antibacterial pharmacological activities, due to the inherent constituents. The aim of this research, therefore, was to analyze the chemical constituents, test antibacterial activities, and observe the mode of action of elephant and emprit ginger rhizome essential oils. Methods: Essential oils isolation was conducted using water and steam distillation method, while microdilution method was adopted in the testing for antibacterial activities against Gram positive and negative bacteria. Furthermore, the mode of action was evaluated using Scanning Electron Microscopy (SEM). Results: The antibacterial activity demonstrated antibacterial activities in the essential oils of elephant and emprit ginger rhizome, with minimal inhibition concentrations (MIC) value of 250-1000 μg.mL^-1 and minimal bacterial concentrations (MBC) value of 500-1000 μg.mL^-1, while chemical evaluation showed the presence of 45 and 38 constituents, respectively. Conclusion: Both essential oils possess antibacterial activities against Gram positive and negative bacteria, with different strengths, which are based on chemical composition. Conversely, SEM micrographs demonstrated the ability for elephant and emprit ginger rhizome essential oils to change the morphology of bacteria.