Phytochemicals are broad & diverse group of compounds that are produced & accumulated in plants. Phytochemical-rich foods include: fruits & vegetables, some cocoa products, as well as whole grains, beverages such as tea & wine. Phytochemicals can alter metabolic & cellular processes.

1. PHYTOCHEMICALS
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Soheila Abachi
Summer 2014

2. Dietary phytochemicals
Phytochemicals are broad & diverse group of
compounds that are produced & accumulated in plants
Phytochemical rich foods include: fruits & vegetables,
some cocoa products, as well as whole grains, beverages
such as tea & wine
Phytochemicals can alter metabolic & cellular
processes
2

3. Dietary phytochemicals
Most dietary studies indicate that diets rich in
phytochemicals are associated with improved health &
provide protection against chronic diseases, or in positive
direction alter chronic disease markers
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4. How do phytochemicals work?
Some possible actions:
Antioxidant : Most phytochemicals have antioxidant
activity & protect our cells against oxidative damage,
reduce risk of developing certain types of cancer
Phytochemicals with antioxidant activity: allyl sulfides
(onions, leeks, garlic), carotenoids (fruits, carrots),
polyphenols including flavonoids (fruits, vegetables, tea)
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5. Hormonal action: Isoflavones, found in soy, imitate
human estrogens and help to reduce menopausal
symptoms & osteoporosis.
Stimulation of enzymes: Indoles, found in cabbages,
stimulate enzymes that make estrogen less effective &
could reduce risk for breast cancer. Other
phytochemicals, which interfere with enzymes, are
protease inhibitors (soy and beans), terpenes (citrus
fruits & cherries).
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6. Interference with DNA replication: Saponins found
in beans interfere with replication of cell DNA, thereby
preventing multiplication of cancer cells. Capsaicin, in
hot peppers, protects DNA from carcinogens
Anti-bacterial effect: allicin from garlic has anti-
bacterial properties
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7. Physical action: Some phytochemicals bind physically
to cell walls thereby preventing adhesion of pathogens
to human cell walls. Proanthocyanidins are responsible
for anti-adhesion properties of cranberry Consumption
of cranberries will reduce risk of urinary tract infections
& will improve dental health
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8. Natural antioxidants
& their health
promoting effects
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12. Antioxidants (Aox) – an overview
Molecules capable of reducing causes or effects of
oxidative stress
Oxidative stress caused by environmental factors,
disease, infection, inflammation, aging (ROS production)
Body produces some endogenous antioxidants, but
dietary antioxidants provide additional defense
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13. Antioxidants – an overview
ROS or “reactive oxygen species”: free radicals &
other oxygenated molecules resulting from these
factors
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Chronic Injury
Cancer, atherosclerosis, CVD, cataracts, immune
dysfunction, Alzheimer´s disease, age-related macular
degeneration, rheumatoid arthritis, aging, etc.
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Oxidative Stress

14. Antioxidants – an overview
Most AOx donate an electron
to Free radicals (FR) without
becoming FR themselves & stops
chain reaction
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Sources of antioxidants in diet

16. Vitamin E, Vitamin C, β-
Carotene, Flavonoids
Polyphenols
Flavonoids Non- Flavonoids
Flavonols→ Quercetin
Flavones
Flavanols→ Catechin
Flavanones
Stilbenes → Resveratrol
Iso-Flavonoids
Anthocyanidins
Vitamins
A E C
Phenolic alcohols
Hydroxybenzoic acids
Hydroxycinnamic acids
Lignans
Dietary antioxidants
Most common dietary AOx

17. Red wine, Cranberries & blueberries (tannins,
resveratrol, flavonoids)
Strawberries (ellagic acid, ellagitannins)
Tea, Chocolate (EGCG & other catechins, tannins)
Onions (quercetin)
Spinach & leafy greens (lutein & zeaxanthin)
Eggs (lutein)
Citrus fruits (Vitamin C)
Plant oils (Vitamin E & omega-3)
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18. Define antioxidant
“a substance that opposes oxidation or inhibits
reactions promoted by oxygen or peroxides”
“synthetic or natural substances that prevent or delay
deterioration of a product, or capable of counteracting
damaging effects of oxidation in animal tissues”
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19. Define antioxidant
“a substance that significantly decreases adverse
effects of reactive species such as ROS or RNS on normal
physiological function in humans
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20. Different types of AOx →different AOx Mechanisms
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Proper AOx: interrupt
propagation of
autoxidation chain
reaction
Preventive AOx:
inhibitors of FR
oxidation reactions
Singlet Oxygen
eliminators: e.g.
carotenes
Reducing agents:
convert hydroperoxides
into stable components
in a non-radical way e.g.
thiols and sulfides.
Synergists of proper
AOx: increase activity
of chain-breaking
AOX in a mixture e.g.
citric acid
Metal chelators: convert
pro-oxidants (especially
iron or copper
derivatives) into stable
products (e.g. Quercetin,
tannins)
Inhibition of pro-
oxidative enzymes

21. Free radicals & ROS
“Reactive Oxygen Species” (ROS): highly reactive free
radicals
ROS form as result of stress, inflammation, human
body’s natural defenses & mostly are formed in
mitochondria, by phagocytes & peroxisomes
Target tissue, proteins, lipids & DNA
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22. Antioxidants?
Prevent formation of ROS & chelate
metals
Scavenge/remove ROS before they
damage important bio-molecules
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23. 3 major classes of phytochemicals
Terpenoids
Alkaloids
Phenolics
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24. “polyphenolic” antioxidants found in plants
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O
OH
OH
OR
HO
OH
quercetin,
a "flavonol"
O
O
OH
OH
OR
HO
OH
catechins OH
HO
OH
resveratrol, a
"stilbene"
On a molecular
level, these
compounds “absorb”
harmful free radicals
& chelate pro-oxidant
metal ions
Modulate cellular
biochemical reactions
& expression of genes
and proteins
associated with
oxidative stress

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1) Simple sugars + phenol groups
2) Lignin & furanocoumarin: inhibit
herbivore/pathogen
3) Lignin: mechanical support
4) Lignan: inhibit fungal growth, insect anti-feedent
5) Anthocyanin: pollinators
6) Flavone / flavonol: absorb UV
7) Phenolic acid: reduce competing plant growth
8) Tannin: protein/enzyme inactivation
How Phenolics protect plants?

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1) Analogues of cellular signals, substrates
2) Induce prostaglandin formation
3) Enzyme inhibitor
4) Estrogenic properties: stilbenes, isoflavones
5) DNA alkylation: furanocoumarin
6) Denaturing effect, hydroxyl groups form
hydrogen/ion bonds with protein
How flavonoids protect plants?

27. Flavonoids
Flavonoids → most common group of plant phenolics
→ +4000 identified in plants
→ Share a common structure (2 Benzene rings and a
central pyran ring) which determines their AOx
functioning
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Flavonols
Flavanols
Flavonones
Anthocyanins
Isoflavones
Flavones

28. Health promotion by Flavonoids
Many flavonoids act as antioxidants
May protect against cancers and heart disease by this
mechanism
More evidence is needed before any claims can be
made for flavonoids themselves as the protective factor in
foods
Particularly when they are extracted from foods or
herbs and sold as supplement
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1) Phenolic acids
2) Stilbenes
3) Flavonoids: flavonols, anthocyanins, flavan-3-ols
4) Lignan
5) Tannins: hydrolysable & condensed
Berry fruit phenolics classification

30. Bluberries
Brain berries
Promote brain function &
prevent the effects of aging
reducing risks of some diseases,
including inflammation & certain
cancer
Promote urinary tract health
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31. Strawberries
Contain Phenolic Acids &
Phenylpropanoids
Aromatic secondary
metabolites
Substitution with carboxyl or
hydroxyl groups generate a bundle
of compounds
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32. Cranberry
Contain Phenolic Acids,
Proanthocyanidins, Anthocyanins,
Flavonoids, Triterpenoids
These compounds have shown:
Antioxidant, anti-inflammatory, &
anti-cancer effects
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33. 1) Isoprene gas: hi-temp., photo-protection
2) Monoterpene: Menthone, α & β-pinene, insect
toxin/ repellent
3) Triterpenoid: cardiac glycoside, highly toxic
4) Glycosylated triterpenoid: saponin, disrupt
fungus cell membrane
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How Terpenes protect plants?

34. 1) Isoprene gas: hi-temp., photo-protection
2) Monoterpene: Menthone, α & β-pinene, insect
toxin/ repellent
3) Triterpenoid: cardiac glycoside, highly toxic
4) Glycosylated triterpenoid: saponin, disrupt
fungus cell membrane
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How Terpenes protect plants?

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1) Highly hydrophobic, interact with bio-membrane
2) Increase fluidity of membrane, uncontrolled efflux
of ion/metabolite
3) modulate membrane protein/receptors, cell
leakage/death
4) Analogues to natural substrates
5) Isoprene units
6) Primary metabolites (plant hormone) Gibberellic
acid, Carotenoid pigment
How Terpenes protect plants?

36. Harvest midsummer
<1 cm in diameter
Very dark purple, almost black
Glossy Skin
Grossulariaceae
Ribes
R. Nigrum
Rich in
Vitamin C, E
Phosphorus,
Potassium

37. Harvest early to late summer
<1.6 cm in diameter
Dark purple
Powdery epicuticular wax
Ericaceae
Vaccinium
V. corymbosum
Rich in
Vitamin C, K
Manganese, Copper

38. Harvest early to midfall
1-2.5 cm in diameter
Dark red to almost black
Hard, shiny skin
Ericaceae
Vaccinium
V. Macrocarpon
Rich in
Vitamin C, E, K
Manganese

39. Harvest late summer to fall
0.6–1 cm in diameter
Red
Shiny skin
Ericaceae
Vaccinium
V. vitis-idaea
Rich in
Vitamin C, E, K
Manganese

40. Harvest early summer
1 cm in diameter
Purple-blue
Powdery epicuticular wax
Caprifoliaceae
Lonicera
L. caerulea
Rich in
Vitamin C, E
Potassium
Calcium
Magnesium
Phosphorus