Fenton reaction applied for screening natural antioxidants

Antioxidant activities of pure chemicals and food additives were compared with that of herb extracts using a method based on the Fenton reaction for screening natural antioxidants. This method detects antioxidants classified as free radical terminators, that may compete with linoleic acid for scavenging -OH radicals. Of the 39 products investigated, 19 were commercial products and 20 were aqueous and ethylic herb infusions. Commercial phenolic and flavonoid products, both hydrophilic and lipophilic, showed strong antioxidant activities, while indole, alkaloid and fs-cyclic products showed no antioxidant activity, as determined by this method. Aqueous infusions of all herbs showed antioxidant properties. Mild oregano, strong oregano, rosemary, sage and mint showed as strong antioxidant properties as pure commercial chemical and food additives, such as hydroquinone, rutin, phenidone, catechol, epicatechin, morin and BHA, in both aqueous and ethylic infusions. Also, the results suggest that, under the experimental conditions, the aqueous extractions of short duration yielded larger quantities of active compounds by reducing the degradation of their antioxidant properties. (c) 2005 Elsevier Ltd. All rights reserved.