Free radicals may play a role in heart disease, cancer and other diseases. Antioxidants, such as vitamins C and E and carotenoids, may help protect cells from damage caused by free radicals. Other naturally occurring antioxidants include flavonoids, tannins, phenols and lignans.
There are different attributes to classify the antioxidants. The first attribute is that antioxidants can be divided into three groups by their mechanism/functions: Primary antioxidants are involved in the prevention of oxidant formation; secondary antioxidants are known to be scavengers of ROS (Reactive oxygen species). and tertiary antioxidants, which are concerned with the repair of damaged biomolecules.
The second attribute is based on enzymatic and non-enzymatic antioxidants.
Primary antioxidants (Free radicals scavengers)
Primary antioxidant can accept free radicals and further delay the initiation step or interrupt the propagation step of auto-oxidation. Primary antioxidants can react with lipid and peroxyl radicals converting them into more stable radicals or non radical products.
They are the chain breaking antioxidants which react with lipid radicals and convert them into more stable products.
Primary or natural antioxidants can be extracted from plants, microorganisms and animal tissues. Antioxidants of this group are mainly phenolics, in structure and include the following: antioxidant minerals, antioxidant vitamins and phytochemicals which include flavonoides, catechins, carotenoids, β-carotene, lycopene, diterpene of, black pepper, thyme, garlic, cumin and their derivatives.
They are very effective radical scavengers during both processing and long-term thermal aging, and are generally non-discoloring.
Secondary antioxidants
These are phenolic compounds that perform the function of capturing free radicals and stopping the chain reactions. They react with hydroperoxides to yield non-radical, non-reactive products. They are compounds produced artificially and added to processed or pre -packaged food to prevent rancidity, browning.
Secondary antioxidants retard oxidation by preventing the proliferation of alkoxy and hydroxyl radicals by decomposing hydroperoxides to yield nonreactive products. Secondary antioxidants can retard lipid oxidation through a variety of mechanisms, including chelating of transition metal ions, oxygen scavenging, replenishing hydrogen to primary antioxidants, absorbing UV radiation and deactivation of reactive species.
The compounds include: Butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT) and propyl gallate (PG).
Classification of antioxidants – based on the functions
