Antioxidant activity and chemical composition of essential oils of three aromatic plants from La Rioja province

Context: The use of many traditional medicinal plants is often hampered by the absence of a proper biochemical characterization, which is essential to identify the bioactive compounds present in it. The essential oils (EOs) of three native species from the La Rioja province were analyzed: Lippia turbinata Griseb and Lippia integrifolia (Griseb.) Hieron (Verbenaceae), and Clinopodium gilliesii (Benth.) Kuntze (Lamiaceae).

Objective: The aim of this study was to evaluate their EOs antioxidant activity (AA) and their chemical composition.

Materials and methods: EOs were analyzed by gas chromatography-mass spectrometry (GC-MS). To enhance the aqueous solubilization of the EOs, EO–water emulsions were prepared (concentration range of 0.1–6?mg?mL^?1). AA was determined using ABTS, DPPH, and peroxyl radical scavenging assays, as well as by the β-carotene bleaching test.

Results: Piperitenone oxide was a major constituent in L. turbinata, pulegone and piperitenone oxide in C. gilliesii, and β-caryophyllene in L. integrifolia. Lippia turbinata EO was the most active ABTS and DPPH radical scavenger (SC₅₀ values of 0.40?±?0.14 and 0.74?±?0.08?mg?mL^?1, respectively). Clinopodium gilliesii EO exhibited the highest hydrogen peroxide scavenging activity (SC₂₅ value?=?1.52?±?0.27?mg?mL^?1). In the β-carotene assay, L. turbinata EO was more effective at inhibiting lipid peroxidation than the other two oils (IC₂₅ value?=?0.15?±?0.04?mg?mL^?1).

Conclusion: Our results suggest that the AA observed can be justified by the presence of oxygenated monoterpenes, mainly piperitenone oxide. Finally, L. turbinata EO might be used as a safe natural antioxidant and food preservative in the food and cosmetic industries.