Study on antioxidant and antimicrobial activities of essentail oil and oleoresins extracted from Vietnamese ginger

Abstract

The biofunctional properties of ginger essential oil and oleoresins including antioxidant and antimicrobial activities were investigated in this study. The essential oil was extracted using the hydro-distillation method and oleoresins were extracted using solvent extraction method (methanol and ethanol). The antioxidant activities of these samples were determined by DPPH scavenging assay, while the antimicrobial activities were determined by the inhibition zone and minimum inhibitory concentration methods against several foodborne pathogens. The yield of ginger essential oil was 1.5%, while the yields of methanol oleoresin and ethanol oleoresin were 10.70% and 6.66%, respectively. Although the extraction yield and antimicrobial activities of methanol oleoresin were higher than ethanol oleoreisn, the antioxidant activities were not significantly different. Ginger oleoresins showed higher antioxidant and antimicrobial activities than ginger essential oil. All samples were found to possess the antimicrobial activities on tested bacteria except B. cereus. Among these samples, methanol oleoresin showed the highest antimicrobial activity against P. aeruginosa (14.0 ± 0.2 mm) and S. aureus (7.50 ± 0.5 mm), followed by ethanol oleoresin and essential oil. As a result, both ginger essential oil and oleoresins are considered to be a natural sources of antioxidants and antimicrobial compounds. Key words: Essential oil; Oleoresins; Hydro-distillation; Solvent extract; Antioxidant; Antimicrobial activity.