Supercritical CO2 extracts and essential oil of ginger (Zingiber officinale R.): Chemical composition and antibacterial activity

This paper reports the assessment of chemical profile and antibacterial activity of ginger (Zingiber officinale Roscoe) roots extracts using supercritical CO2 as solvent. The effects of the supercritical extraction conditions on the chemical composition and antibacterial activity of the extracts obtained were evaluated and compared with essential oil of ginger obtained from hydrodistillation technique. The extractions using CO2 were performed in a laboratory scale unit at pressures of 10.0 MPa, 17.5 MPa and 25.0 MPa and at 293.15 K, 313.15 K and 333.15 K. The operating conditions tested achieved a maximum yield of 2.62 wt% for the CO2 extraction and 1.79 wt% for the hydrodistillation. When CO2 was used as the solvent, the pressure and temperature had a significant effect on the extraction yield. The chemical profiles determined by gas chromatography were found to be similar for the two methods; however, the quantities of the compounds extracted were different. The main compounds present in the extracts obtained using CO2 were α-zingiberene, β-sesquiphellandrene, α-farnesene, geranial, β-bisabolene and β-eudesmol. For the oil obtained by hydrodistillation, α-curcumene, geranial and camphene were the most abundant compounds. Antibacterial activity assays were performed on the ginger extracts and essential oil using the agar well method. The extracts obtained using supercritical CO2 presented antibacterial effects against Gram-positive bacteria. The oil obtained by hydrodistillation differed from the other samples tested and had a lower capacity for inhibition of Pseudomonas aeroginosa bacteria than the supercritical extract. For the Gram-negative bacterias Salmonella typhimurium and Shigella flexneri the oil showed slight inhibition.