• Specificity of free radical quenching
• Metal chelating activity
• Interaction with other antioxidants
• Effects on gene expression
Other criteria are important when considering preventive
or therapeutic applications:
• Absorption and bioavailability
• Concentration in tissues, cells, and extracellular
fluid
• Location (in aqueous or membrane domains or in
both?)
A substance need not excel in meeting all these
criteria to be considered a good antioxidant. For example,
vitamin E acts only in the membrane or lipid domains,
its dominant action is to quench lipid peroxyl
radicals, and it has little or no activity against radicals
in the aqueous phase, yet it is considered one of the
central antioxidants of the body. Epidemiological studies