Antioxidants are substances that protect cells from the damage caused by unstable molecules known as free radicals.
Antioxidants can be divided into three groups by their mechanism:
1. Primary antioxidants are involved in the prevention of oxidant formation;
2. Secondary antioxidants, which are important preventive antioxidants that function by retarding chain initiation; and
3. Tertiary antioxidants, which are concerned with repair the oxidized molecules through sources like dietary or consecutive antioxidants
Secondary antioxidants can work indirectly on limiting lipid oxidation. The secondary antioxidant mechanisms may include 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). EDTA (ethylenediaminetetraacetic acid) is an example of an excellent metal chelating antioxidant used in the food industry.
In human body, secondary antioxidant includes glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH). G6PDH generates NADPH. GR is required to recycle the reduced glutathione (GSH) using secondary enzyme GR and NADPH.
Secondary antioxidants
 |
| EDTA Structure |
