Distillation time effecting on the composition of Origanum floribundum essential oils and their antioxidant and antimicrobial activities

Z Naturforsch C J Biosci. 2020 Oct 1;/j/znc.ahead-of-print/znc-2020-0102/znc-2020-0102.xml. doi: 10.1515/znc-2020-0102. Online ahead of print.

Abstract

The essential oils (EOs) of Origanum floribundum Munby, an aromatic and medicinal plant endemic in Algeria, were extracted by different hydrodistillation times (30 min, 1, 2 and 3 h) and analyzed by GC and GC-MS. The chromatographic analysis showed that thymol (32.7-45.0%), p-cymene (16.8-23.1%) and γ-terpinene (21.6-28.7%) were the most prominent components of the oils. The antioxidant ability was measured using the reductive potential, thiobarbituric acid reactive substances (TBARS) assay and the inhibition of free radicals DPPH● and ABTS●+. Antibacterial activity was assessed by the disc diffusion method against three bacteria (Escherichia coli, Staphylococcus aureus and Bacillus subtilis) and one fungus (Candida albicans). Minimal inhibitory concentrations (MICs) were determined using a microdilution method. Thymol is one of the compounds of EOs, which are widely reported as very biologically active. Although the oil isolated for 30 min was the less-thymol rich, it was the most active with all the antioxidant tests. In the most cases, the antimicrobial activity showed the best results with oils isolated for 30 min and 3 h (MIC = 0.25-1.75 μL/mL). These results suggest that it might be possible to isolate the EO from this plant for a minimum distillation time to obtain oil that can give maximum biological activities.

Keywords: Origanum floribundum; antimicrobial activity; antioxidant activity; essential oil; time of extraction.