Life on earth, with the exception of anaerobic organisms like some bacteria and fungi, evolved around oxygen. Essential to most complex life, it plays a major role in our metabolism, yet also brings about our ultimate demise, for oxygen is a highly reactive molecule.
First discovered in the late eighteenth century and hailed as the 'Elixir of Life', oxygen damages living organisms by producing reactive oxygen species or free radicals as well as bleaching agents such as hydrogen peroxide. We have all witnessed oxygen's' destructive power as it ultimately converts iron to rust or quickly browns freshly cut fruit. To survive this paradox, life has come up with an ingenious solution: antioxidants.
Antioxidants - a brief history
Towards the end of the fifteenth century, Columbus' courageous voyage heralded the beginning of the Age of Sail and exploration. Fantastic voyages lasting many years discovered great lands and naval warfare flourished. But months at sea soon presented new challenges. A terrible scourge afflicted sailors whose diet was totally devoid of fresh fruit and vegetables: Scurvy. Known as the 'Mariners Disease' it could kill swiftly and ship-owners of the time routinely counted on a 50% death rate at sea. It was not until almost 200 years later that an English naval surgeon, James Lind, successfully trialed citrus juice as a cure for scurvy - and it would be almost another 200 years before the active ingredient, ascorbic acid (meaning anti-scorbutic) or Vitamin C, was first isolated.
Towards the end of the nineteenth century, it became widely known that many biological and industrial processes benefited from the use of antioxidants, yet the mechanism of how they worked remained unclear. The identification of Vitamin A, C and E was a major step forward in realizing that antioxidants prevent or slow the oxidization of other molecules.
The mechanism of action of antioxidants
Antioxidants come in many forms. Among the most widely known are the vitamins C and E as well as ß-carotene. Others include glutathione, lipoic acid, uric acid, melatonin, ubiquinone (Coenzyme Q10) and a complex network of antioxidant enzymes. Broadly classified into two divisions, hydrophilic (soluble in water) or hydrophobic (soluble in lipids or fats), antioxidants play a vital role in preventing oxidative stress in living organisms and act as preservatives for food and cosmetics as well as other industrial uses.
The complex system of antioxidants maintained by organisms serves to slow or prevent oxidative damage to components within cells such as proteins and DNA. This is generally achieved by terminating the chain reactions of cell damaging free radicals and by the inhibition of other oxidation reactions. Some antioxidants are recycled by the body and are thus able to be used again; others are referred to as suicidal. Whilst humans have the ability to produce important antioxidants such as glutathione, others need to be ingested from the food we eat. Vitamin C, for example, cannot be synthesized although most other animals are able to do so.
The health effects of antioxidants, their role in preventing disease and the benefits of supplementation is the subject of ongoing research, yet there is no doubt that, without the intricate system of antioxidants, aerobic life could not exist.