Abstract
Essential oils (EOs) have promising antioxidant activities which are gaining interest as natural alternatives to synthetic antioxidants in the food and cosmetic industries. However, quantitative data on chain-breaking activity and on the kinetics of peroxyl radical trapping are missing. Five phenol-rich EOs were analyzed by GC-MS and studied by oxygen-uptake kinetics in inhibited controlled autoxidations of reference substrates (cumene and squalene). Terpene-rich Thymus vulgaris (thymol 4%; carvacrol 33.9%), Origanum vulgare, (thymol 0.4%; carvacrol 66.2%) and Satureja hortensis, (thymol 1.7%; carvacrol 46.6%), had apparent kinh (30 °C, PhCl) of (1.5 ± 0.3) × 104, (1.3 ± 0.1) × 104 and (1.1 ± 0.3) × 104 M−1s−1, respectively, while phenylpropanoid-rich Eugenia caryophyllus (eugenol 80.8%) and Cinnamomum zeylanicum, (eugenol 81.4%) showed apparent kinh (30 °C, PhCl) of (5.0 ± 0.1) × 103 and (4.9 ± 0.3) × 103 M−1s−1, respectively. All EOs already granted good antioxidant protection of cumene at a concentration of 1 ppm (1 mg/L), the duration being proportional to their phenolic content, which dictated their antioxidant behavior. They also afforded excellent protection of squalene after adjusting their concentration (100 mg/L) to account for the much higher oxidizability of this substrate. All investigated EOs had kinh comparable to synthetic butylated hydroxytoluene (BHT) were are eligible to replace it in the protection of food or cosmetic products.
Highlights
All investigated essential oils (EOs) had kinh comparable to synthetic butylated hydroxytoluene (BHT) were are eligible to replace it in the protection of food or cosmetic products
Components with peak area
To gain a more accurate measurement of the relative abundance of components in each oil in the absence of calibration with authentic standards of individual components, we turned to the flame ionization detector (FID) method, since
Summary
Among the many properties that are often attributed to plant essential oils (EOs), the antioxidant property certainly stands out [1]. When paired with the antimicrobial activity, which has been extensively documented for many essential oils in recent and less recent literature [2,3,4], the additional antioxidant activity makes those natural materials extremely attractive as multi-functional preservatives, e.g., for food products, able to control spoilage caused both by microbial metabolism and by air oxidation [3,5]. Consumer choice has progressively oriented food technologists toward more natural and (expectedly) safer alternatives to synthetic additives, which has boosted the interest in plant-derived bioactives, including essential oils [1,2,3,5,6]
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