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PHYTOCHEMICALS

Soheila Abachi Summer 2014

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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

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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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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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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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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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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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Natural antioxidants

& their health

promoting effects

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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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Antioxidants – an overview

ROS or “reactive oxygen species”: free radicals &

other oxygenated molecules resulting from these

factors

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

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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

Vitamin E, Vitamin C, β-Carotene, Flavonoids

Polyphenols

Flavonoids Non- Flavonoids

Flavonols→ QuercetinFlavonesFlavanols→ Catechin Flavanones

Stilbenes → Resveratrol

Iso-FlavonoidsAnthocyanidins

Vitamins

A E CPhenolic alcoholsHydroxybenzoic acidsHydroxycinnamic acidsLignans

Dietary antioxidants

Most common dietary AOx

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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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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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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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Different types of AOx →different AOx MechanismsProper 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

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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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Antioxidants?

Prevent formation of ROS & chelate

metals

Scavenge/remove ROS before they

damage important bio-molecules

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3 major classes of phytochemicals

Terpenoids

Alkaloids

Phenolics

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“polyphenolic” antioxidants found in plants

O

OH

OH

OR

HO

OH

cyanidin, an "anthocyanin"

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 formation3)Enzyme inhibitor 4)Estrogenic properties: stilbenes, isoflavones5)DNA alkylation: furanocoumarin6)Denaturing effect, hydroxyl groups form

hydrogen/ion bonds with protein

How flavonoids protect plants?

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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

FlavonolsFlavanolsFlavononesAnthocyaninsIsoflavonesFlavones

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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 acids2)Stilbenes 3)Flavonoids: flavonols, anthocyanins, flavan-3-ols4)Lignan5)Tannins: hydrolysable & condensed

Berry fruit phenolics classification

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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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Strawberries

Contain Phenolic Acids &

Phenylpropanoids

Aromatic secondary

metabolites

Substitution with carboxyl or

hydroxyl groups generate a bundle

of compounds

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Cranberry

Contain Phenolic Acids,

Proanthocyanidins, Anthocyanins,

Flavonoids, Triterpenoids

These compounds have shown:

Antioxidant, anti-inflammatory, &

anti-cancer effects

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1)Isoprene gas: hi-temp., photo-protection2)Monoterpene: Menthone, α & β-pinene, insect

toxin/ repellent 3)Triterpenoid: cardiac glycoside, highly toxic 4)Glycosylated triterpenoid: saponin, disrupt

fungus cell membrane

How Terpenes protect plants?

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1)Isoprene gas: hi-temp., photo-protection2)Monoterpene: Menthone, α & β-pinene, insect

toxin/ repellent 3)Triterpenoid: cardiac glycoside, highly toxic 4)Glycosylated triterpenoid: saponin, disrupt

fungus cell membrane

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?

Harvest midsummer <1 cm in diameterVery dark purple, almost black Glossy Skin

Grossulariaceae Ribes R. Nigrum

Rich in Vitamin C, EPhosphorus, Potassium

Harvest early to late summer <1.6 cm in diameterDark purple Powdery epicuticular wax

Ericaceae Vaccinium V. corymbosum

Rich in Vitamin C, KManganese, Copper

Harvest early to midfall 1-2.5 cm in diameterDark red to almost blackHard, shiny skin

Ericaceae Vaccinium V. Macrocarpon

Rich in Vitamin C, E, K Manganese

Harvest late summer to fall0.6–1 cm in diameterRed Shiny skin

Ericaceae Vaccinium V. vitis-idaea

Rich in Vitamin C, E, K Manganese

Harvest early summer1 cm in diameterPurple-bluePowdery epicuticular wax

Caprifoliaceae Lonicera L. caerulea

Rich in Vitamin C, EPotassium CalciumMagnesiumPhosphorus