ABSTRACT
Introduction .................................................................................................................................... 73 Generation of Reactive Oxygen Species (ROS)............................................................................ 74 Prevention of Oxygen Radical-Induced Damage by
Echinacea
Constituents............................. 76 Phenolics ................................................................................................................................. 76 Flavonoids ............................................................................................................................... 79 Anthocyanins........................................................................................................................... 82
Effects of
Echinacea
Extracts on Nitrogen Radicals .................................................................... 83 Effects of
Echinacea
Extracts on Oxidative Enzymes.................................................................. 84 Final Comments ............................................................................................................................. 85 References ...................................................................................................................................... 85
Living organisms are exposed to 20.93% oxygen in air, which contributes to a dependency on biological oxidation reactions as a source of energy required for natural growth and metabolism. Under normal conditions, 2% of the oxygen consumed by mitochondria is incompletely reduced, thus resulting in the production of oxygen radicals (Boveris and Chance, 1973). If mitochondria electron transport is compromised, the percentage of oxygen incompletely reduced will increase. There is a potential, therefore, for a relatively small percentage of oxygen derived from systemic respiration to be transformed to bioactive agents, which in turn can ultimately lead to peroxidation reactions of cellular constituents that are composed of nucleic acids, lipids, proteins, and carbohydrates. In addition to endogenously derived reactive oxygen species (ROS), living organisms can also be exposed to ROS derived from exogenous sources such as environmental exposure to ultraviolet light, smoking, and pollution. Besides oxygen, nitrogen also has a central role in biology, since nitrogen generates a series of free radical or nonradical species (reactive nitrogen species, RNS). Common reactive oxygen and nitrogen species include superoxide anion (O
), hydroxyl radical (
∑OH), peroxyl radical (LOO
∑), alkoxyl radical (LO
∑), nitric oxide (NO
∑), nitrogen dioxide (NO
), and peroxynitrite (ONOO
-) (Halliwell and Aruomoa, 1997). A list of reactive oxygen and nitrogen species is shown in Table 6.1.
