Antioxidants

There are three major types of compounds, which can directly suppress free radical forma-

tion: antioxidants, free radical scavengers, and chelators. (Antioxidants and free radical

scavengers are usually considered to be synonyms, although not always. For example, ethanol

is a hydroxyl radical scavenger but was never regarded as an antioxidant. Antioxidant is the

oldest term, which at the beginning had been applied for the description of inhibitors of

oxidative processes, which are able to react with peroxyl radicals. Now, this term is frequently

applied to all free radical inhibitors.) In addition to direct antioxidants, there are two other

important groups of free radical inhibitors: antioxidant enzymes (Chapter 25) and the

compounds possessing indirect antioxidative properties. Compounds having indirect antiox-

idative properties may affect the formation of free radicals by an indirect way, for example by

inhibiting the activity of prooxidant enzymes.