De werking van knoflook*
Al langer zijn de gezonde eigenschappen van de bioactieve stof allicine in knoflook wetenschappelijk aangetoond doch nog steeds was onbekend hoe allicine zijn werk als antioxidant doet. In deze studie heeft men onderzocht hoe dat gebeurt. De allicine in de knoflook vormt het sulfenic zuur bij het uiteen vallen. Dit zuur reageert onmiddellijk met vrije radicalen om die onschadelijk te maken. Alhoewel
allicine ook in andere voeding zit zoals prei, uien en bieslook hebben deze andere gezonde eigenschappen vermoedelijk als gevolg van een kleinere hoeveelheid sulfenic zuur die gevormd wordt.
Health Benefits Of Garlic Traced To Acid Produced In Decomposing Organic Compound
A Queen's-led team has discovered the reason why garlic is so good for us.
Researchers have widely believed that the organic compound, allicin - which gives garlic its aroma and flavour - acts as the world's most powerful antioxidant. But until now it hasn't been clear how allicin works, or how it stacks up compared to more common antioxidants such as 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," says Chemistry professor Derek Pratt, who led the study. "If allicin was indeed responsible for this activity in garlic, we wanted to find out how it
worked."
The research team questioned the ability of allicin to trap damaging radicals so effectively, and considered the possibility that a decomposition product of allicin may instead be responsible. Through experiments with synthetically-produced allicin, they found that an acid produced when the compound decomposes rapidly reacts with radicals.
Their findings are published in the international chemistry journal Angewandte Chemie.
"Basically the allicin compound has to decompose in order to generate a potent antioxidant," explains Dr. Pratt, who is Canada Research Chair in Free Radical Chemistry. "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."
The researcher is confident 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," says Dr. Pratt. "I think we have taken the first step in uncovering a fundamental chemical mechanism which may explain garlic's medicinal benefits."
Along with onions, leeks and shallots, garlic is a species in the family Alliaceae. All of these other plants contain a compound that is very similar to allicin, but they do not have the same medicinal properties. Dr. Pratt and his colleagues believe 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.
The study was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Ontario Ministry of Innovation. Other members of the research team are Queen's Chemistry post-doctoral researcher Vipraja Vaidya and Keith Ingold, from the National Research Council of Canada.
Source: Nancy Dorrance
Queen's University (Maart
2009)
