Antioxidant and Anti-Inflammatory Activities of Essential Oils: A Short Review

Miguel, Maria Graça

The Rancimat method is an automated test that measures the conductivity of low molecular weight fatty acids (formic acid) produced during the auto-oxidation of lipids at 100 ºC or above [5] . The antioxidant activity of essential oils of five spice plants used in the Mediterranean diet that was evaluated through the TBARS method [52] was also evaluated through the Rancimat method in which the lipid substrate was lard. The system was heated at 120 ºC and an air flow of 20 L/h was constantly blown into the mixture. The end of the induction period was characterized by the sudden increase of water conductivity, due to the dissociation of volatile carboxylic acids. Their results showed that the oils of Thymus vulgaris and Origanum vulgare L. showed the best antioxidant activity index, as determined by the Rancimat method, but less than the activity of BHT (synthetic standard). Carvacrol was the main component of the Origanum vulgare oil. In this case, an oil rich in phenolic components (oregano) and the other one (thyme) without great levels of these components presented similar activities, in contrast to that reported for the TBARS, in which thyme possessed the best activity [52] . This is a good example in which diverse methods of antioxidant evaluation may give rise different results, showing therefore the importance of using several methods to evaluate the enatioxidant activity of samples.