Impact of fractional distillation on physicochemical and biological properties of oregano essential oil of Lippia graveolens H.B.K. grown wild in Mexico

Abstract

The aim of this work was to evaluate the impact of fractional distillation on the physicochemical and biological properties of oregano essential oil obtained from Lippia graveolens H.B.K. Dry vacuum fractional distillation allowed the division of oregano essential oil into two distinct fractions. The first fraction was rich in ρ-cymene (45.32%) and γ-terpinene (19.14%), while the second fraction had enrichments on the phenolic thymol and carvacrol components (47.63% and 35.56%, respectively), reaching up to 83% of the total chemical composition. In addition, it was shown that fractionation influenced the biological properties of the essential oil. The fraction enriched on thymol and carvacrol showed a higher antioxidant activity than the complete oregano essential oil and the terpenic fraction, as measured by the DPPH method. Moreover, the phenolic fraction produced a concentration-dependent viability decrease on HeLa, Hep2 and A-549 cancer cell lines. The cytotoxic activity of the phenolic fraction was higher compared to that of complete oregano essential oil as well as that of the terpenic fraction. It can be concluded that dry vacuum fractional distillation is an effective separation method that could be used to rectify and improve the quality of oregano essential oils, making them more attractive in the market. As another benefit, the fractions generated could be used for different purposes. In practice, the terpenic fraction, for example, could be used in flavouring and fragrance industries. Regarding the phenolic fraction, new and deeper studies are needed to establish its potential use in food safety and pharmaceutical industries.