Contact: Nancy Dorrance
Queen's chemist sheds light on health benefits of garlic
Researchers trace benefits to acid produced in decomposing organic compound
Kingston, ON – A Queen's-led team has discovered the reason why garlic is so good for us.
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.
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
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 January 2009 issue of the international chemistry journal
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."
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."
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.
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.
Nancy Dorrance, Queen's News & Media Services, 613.533.2869
Alissa Clark, Queen's News & Media Services, 613.533.6000, ext. 77513
broadcasters: Queen's has facilities to provide broadcast quality audio
and video feeds. For television interviews, we can provide a live,
real-time double ender from Kingston via fibre optic cable. Please call