Onions- A Global Benefit to
Health
Gareth Griffiths, Laurence
Trueman, Timothy Crowther, Brian
Tomas and Brian Smith
Onion FAQ.
• Bulb onions likely originated in central
Asia, but are not found in the wild.
• Onions are grown in every part of the
world where plants are farmed.
• Onion is the second most important
horticultural crop world wide.
Two Chemical Classes With
Perceived Health Benefits.
Flavonoids:
-Anthocyanins (Red)
-Quercetins (Yellow)
Alkyl cysteine sulphoxides (ACSOs):
-Flavor precursors cleaved by alliinase enzyme
ACSOs and Associated Breakdown
Products
• Three ACSOs are present in intact onion tissue.
• Upon hydrolysation by alliinase, and subsequent
spontaneous reactions with each other and
nearby compounds, ACSOs give rise to ~50
sulphur containing compounds.
• This wide array of sulphur containing
compounds contribute to onion flavor and are
reported to provide benefits to human health.
Factors Affecting final composition
of ACSO breakdown products.
• Initial concentration and ratios of the three
ACSO species.
• Availability of alliinase enzyme (tissue
disruption).
• Type and concentration of other compounds in
the environment with witch ACSO breakdown
products react.
• pH & temperature of the environment.
ACSO Breakdown
Reported Health Benefits of ACSO
breakdown products in Onion
• Anticancer activity through modulation of enzymes
involved in metabolization of carcinogenic compounds.
• Possible lowering of serum cholesterol.
• Lowering systolic blood pressure & thinning the blood
(only compounds found in uncooked pungent cultivars).
• Antiasthmatic activity, suppressing reactions leading to
bronchial restriction.
• Antifungal and antibacterial properties.
Flavonoid Compounds in Onion
Flavonols:
• Yellow compounds concentrated in the skin of
the onion.
• Sixteen flavonol compounds have been
identified in onion.
Anthocyanins:
• Red compounds.
• Four anthocyanin compounds have been
identified in onion.
Reported Health Benefits of
Flavonoids in Onion
• Antioxidant effects of flavonoids help to protect
cells from oxidative stress resulting from free
radical damage, as well as reducing cancer
rates by protecting DNA from oxidative damage.
• Possible lowering of serum cholesterol by
quercetin compounds.
• Phenolic flavonoid compounds may provide
some antibiotic activity.
Garlic as an Antioxidant:
The Good The Bad and The Ugly
S.K. Banerjee, Pulok K.
Mukherjee and S.K. Maulik
Garlic Health FAQ.
• Garlic has played an important dietary and
medicinal role for centuries.
• The sale of medicinal garlic preparations is
on par with that of many prescription
drugs.
• A wide array of health claims are made for
garlic and its various preparations.
Health Benefits Attributed to Garlic
• Prevention of Cardiovascular disease.
• Reduced Cancer Risk.
• Treatment of microbial infections.
• Antidote for heave metal poisoning.
• Hepatoprotective.
Garlic and Human Health
• Garlic consumption has been recognized
in reducing rates of cancer and
Cardiovascular disease.
• This effect is thought to be largely due to
the antioxidant properties of the many
organosulphur compounds found in garlic
preparations.
Various Garlic Preparations
Examined for Health Effects.
• Raw Garlic
• Heat Treated Garlic
• Garlic Powder
• Aged garlic Extract
• Garlic Oil (steam distilled, oil macerated, ether
extract)
• Garlic Protein
Garlic preparation method, effects on
various oxidative stress conditions.
Garlic Organosulphur Compounds
• When Garlic is crushed Allinase enzyme acts on
Alliin to form allicin.
• Allicin has both antioxidant and oxidative
properties.
• The many breakdown products of Allicin vary
across different preparation methods.
• Different garlic preparations are reported to have
varying antioxidant and disease fighting
properties.
Garlic Organosulphur Compounds
Garlic Organosulphur Compounds
Reported Effects.
• Antioxidant (free radical scavenging)
protecting DNA, Proteins, Lipids, and other
compounds from oxidative damage.
• Increased endothilial cell NO production,
making blood vessels more elastic.
• Decreased hepatic cytochrome P450,
protecting the liver from toxin
(acetominophen) induced injury.
Negative Effects Resulting From
large Doses of Garlic.
• Bad Breath
• Anemia.
• Weight loss.
• Lysis of red blood cells.
• Altered cellular architecture in the heart,
liver and kidneys.