Determination of Antioxidant Activity and Sun Protection Factor of Commercial Essential Oils

Aromatic plants have been used since antiquity as great potential sources of therapeutics in folk medicine and as preservatives in foods, because they contain many biologically active compounds. Among all, essential oils (EOs) are an important group of secondary metabolites that, even if not essential for plant survival, are significant for their allelopathic effects, either negative or positive, on microbes and the environment. From the chemical point of view, EOs are highly complex mixtures involving from several tens to hundreds of different types of volatile compounds, such as terpenoids, oxygenated terpenes, sesquiterpenes, and hydrocarbons. EOs have been widely used for their virucidal, bactericidal, fungicidal, anticancer, antioxidant, and antidiabetic activities, and the biological properties of EOs are strictly linked to their chemical composition. This study was carried out on the following commercial EOs: bergamot (Citrus bergamia), bitter orange (Citrus aurantium), clove (Eugenia caryophyllata), eucalyptus (Eucalyptus globulus), fennel (Foeniculum vulgare dulce), helichrysum (Helicrysum italicum), lavender (Lavandula officinalis), lemon (Citrus limon), oregano (Origanum vulgare), palmarosa (Cymbopogon martini), star anise (Illicium verum), tangerine (Citrus reticulate), tea tree (Melaleuca alternifolia), turmeric (Curcuma longa), Chinese yin yang (mix of Eucalyptus aetheroleum, Cymbopogon citratus, Caryophylli aetheroleum, Mentha piperita, Pinus sylvestris, Salvia rosmarinus, Lavandula officinalis, Foeniculum vulgare, Salvia officinalis, Illicium verum, Mentha arvensis, Abies siberica), Japanese yin yang (Mentha arvensis), and ylang ylang (Cananga odorata). The EOs were tested for the in vitro determination of antioxidant activity (DPPH assay) and of the sun protection factor (SPF) by means of UV-Vis spectrophotometry. These biological activities allowed us to evaluate their potential application as natural preservatives and active ingredients in foods, beverages, and cosmetics, as well as in galenic preparations. The results show that amongst the seventeen EOs studied, clove showed the highest antioxidant activity, with an EC50 of 0.36 µL/mL, followed by Chinese yin yang (5.35 µL/mL), oregano (11.58 µL/mL), and ylang ylang (12.71 µL/mL). Moreover, higher SPF values were recorded for bergamot (9.74), star anise (9.28), fennel (9.10), bitter orange (8.96), ylang ylang (8.41), and clove (8.26). Overall, clove and ylang ylang EOs resulted the best potential candidates as natural preservatives, as they showed the highest health-promoting values, because at the same time, they provided protection against oxidative stress and fought free radicals that may form after sun radiation exposure.