Identification of Chemical Compounds, Antioxidant Potential, Phenolic Content and Evaluation of Inhibitory and Bactericidal/Fungicidal Effects of Ginger Essential Oil on Some Pathogenic Microorganisms in Vitro

Background and Objectives: Ginger (Zingiber officinale) has been used as medicine and spice in Iran, China, and India since ancient times. Currently ginger is used in many foods, beverages and pharmaceutical agents. The purpose of this research was to evaluate the antibacterial and antifungal activities of ginger essential oil on some pathogenic strains and to determine the chemical compounds, total phenolic content, and antioxidant activity of the ginger essential oil using 2,2-diphenyl-1-picrylhydrazyl.   In this experimental study, identification of chemical compounds of the ginger essential oil and their quantitative measurement was performed using gas chromatography and gas chromatography- mass spectrometry devices. The antimicrobial properties were determined by various qualitative and quantitative methods [disc diffusion agar, minimum inhibitory concentration (MIC), and minimum bactericidal/fungicidal concentration (MBC/MFC)]. Measurement of total phenol and antioxidant potential were carried out by Seevers and Daly colorimetric and radical scavenging methods, respectively. The data were analyzed using one-way ANOVA and Tukey test.   In this study, the highest and the lowest diameters of the inhibition zone at the concentration of 100mg/ml were observed for Candida albicans and Salmonella typhi, respectively. The MIC of the ginger essential oil was equal to 50, 50, 25, 6.25, 12.5, 12.5, 6.25, and 6.25mg/ml for Pseudomonas aeruginosa, Salmonella typhi, Escherichia coli, Staphylococcus aureus, Listeria innocua, Bacillus cereus, Candida albicans, and Aspergillus niger, respectively. The MBC/MFC of the essential oil, were higher than MIC. Zingiberene (29.48%) was the major compound in the ginger essential oil, and the antioxidant activity (IC50) and total phenolic content of ginger essential oil were equal to 93.45μg/ml and 76.65 mg GAE/g, respectively. Conclusion: The results of the current study showed that the effect of ginger essential oil on Gram-positive bacteria was higher as compared to Gram-negative bacteria. Therefore, clinical trials are suggested for future researches.