A group of scientists have found out why garlic is health-wise beneficial.
The Queen's-led researchers highlight the fact that garlic derives its aroma and flavour from an organic compound called allicin, which is considered to be the world's most powerful antioxidant.
However, they add, none of the studies conducted to date have made it clear as to how allicin works, or how it stacks up compared to more common antioxidants like Vitamin E and coenzyme Q10, which stop the damaging effects of radicals.
"We didn't understand how garlic could contain such an efficient antioxidant, since it didn't have a substantial amount of the types of compounds usually responsible for high antioxidant activity in plants, such as the flavanoids found in green tea or grapes. If allicin was indeed responsible for this activity in garlic, we wanted to find out how it worked," says Chemistry professor Derek Pratt, who led the study.
The researchers believed that the ability of allicin to trap damaging radicals so effectively might be attributed to a decomposition product of it.
Thus, they conducted some experiments with synthetically-produced allicin, which showed that an acid produced when the compound decomposes rapidly reacts with radicals.
"Basically the allicin compound has to decompose in order to generate a potent antioxidant. The reaction between the sulfenic acid and radicals is as fast as it can get, limited only by the time it takes for the two molecules to come into contact. No one has ever seen compounds, natural or synthetic, react this quickly as antioxidants," says Dr. Pratt, who is Canada Research Chair in Free Radical Chemistry.
Describing the study in the international chemistry journal Angewandte Chemie, the researcher expressed confidence that a link exists between the reactivity of the sulfenic acid and the medicinal benefits of garlic.
"While garlic has been used as a herbal medicine for centuries and there are many garlic supplements on the market, until now there has been no convincing explanation as to why garlic is beneficial. I think we have taken the first step in uncovering a fundamental chemical mechanism which may explain garlic's medicinal benefits," says Dr. Pratt.
While onions, leeks, and shallots contain a compound that is very similar to allicin, they do not have the same medicinal properties as garlic.
Dr. Pratt says that this is due to a slower rate of decomposition of the allicin analogs in the onions, leaks and shallots, which leads to a lower level of sulfenic acid available to react as antioxidants with radicals.