Antioxidant activity of essential oils of five spice plants widely used in a Mediterranean diet

The oxidative degradation of lipids is one of the main factors limiting the shelf-life of food products. In recent years, several undesirable disorders have been detected as side-effects of using commonly used synthetic antioxidants. Apart from their use as aroma additives in food, essential oils from aromatic plants have shown potential for use in small amounts in fat-containing food systems to prevent or delay some types of chemical deterioration that occur during storage. Using a multiple-method approach, the antioxidant activity of the essentials oils from several spices widely used in Mediterranean countries was tested: oregano (Origanum vulgare), thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), sage (Salvia officinalis) and clove (Syzygium aromaticum). Their total phenolic compound content was also determined. The clove essential oil had the highest amount of total phenols (898.89 mg/l GAE) and showed the highest percentage inhibition of DPPH radical (98.74%) and the highest FRAP value (1.47TEAC). The thyme essential oil produced the highest percentage inhibition of TBARS (89.84%). All the essential oils studied were capable of chelating iron(II), the rosemary essential oil producing the highest effect (76.06%) in this respect. The oregano essential oil had the highest antioxidant activity index in the Rancimat test. Copyright (C) 2009 John Wiley & Sons, Ltd.