Peroxyl Radical Trapping Antioxidant Activity of Essential Oils and Their Phenolic Components

Essential oils (EOs) are gaining importance as sustainable food antioxidants, but kinetic data on peroxyl radical trapping are missing. Thirteen EOs from 11 botanical species were studied in the inhibited autoxidation of cumene by oxygen-uptake kinetics. EOs of Juniperus oxycedrus, Syzygium aromaticum, Thymus vulgaris, Thymbra capitata, Betula alba, Pimenta racemosa, and Satureja montana, containing 23-86% phenolic components by gas chromatography/mass spectrometry (GC-MS) analysis, afforded inhibition rate constants k_inh in the order of 10⁴ M^-1 s^-1 at 30 °C similar to reference butylhydroxytoluene (2,6-di-tert-butyl-4-methylphenol) (BHT). They matched or outperformed BHT in the protection of olive oil. The EOs Daucus carota and Cedrus atlantica with <1% phenols and those of Apium graveolens and Tagetes minuta with no phenolics had no chain-breaking activity. Key components carvacrol, thymol, eugenol, dihydroeugenol, umbelliferone, conyferyl alcohol, o-cresol, m-cresol, p-cresol, 4-allylphenol, 2,3-xylenol, 2,4-xylenol, and phenol had k_inh in the range of 10³-10⁴ M^-1 s^-1 and, along with EOs containing them, could potentially replace BHT in the protection of food products.