Midterm 3 (Lecture 12) Flashcards

1
Q

Phytochemicals

A

Non nutritive Substances found in plants

Proposed to contribute toward disease prevention

> 900 classes

Examples: alicia in garlic
Flavonoids
Phytoestrogens
Catechins
Lycopene

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2
Q

Plant polyphenols

A

One of the most numerous and ubiquitous groups of plant metabolites - Integral part of human diet

Contribute to plant morphology (pigmentation)

Essential to plant physiology - involved in growth and reproduction, pathogen resistance

Common structural feature:
Aromatic ring with at least one hydroxyl group

Derived from a common intermediate, phenylalanine, or a close precursor, shikimic acid

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3
Q

Plant polyphenol classes

A

Generally divided into 4 classes:
- phenolic acids
-Flavonoids
- stillbenes
-Lignans

Based on the number of phenol rings and on the structural elements that bind these rings to one another

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4
Q

What influences amount of polyphenols in plants

A
  • light
  • genetic factors
  • environmental conditions
  • ripeness
  • variety
  • processing, storage
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5
Q

Polyphenols in food

A

Contribute toward the sensory qualities
- bitterness
- Astringency
- colour
- flavour
- door
- oxidative stability

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6
Q

Polyphenols as anti nutrients

A

Means they interfere with bioavailability

Macronutrients
- bind protein to reduce absorption- increased fecal nitrogen
- polyphenol must be highly polymerized and most low molecular weight polyphenols do not do this

Micronutrients
- form complexes with many minerals and reduce absorption (iron, copper)

However
- renewed interest due to antioxidant capacities
- numerous potential beneficial human health effects

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7
Q

Flavonoids

A

Originally named Vitamin P for pigment by Rusznyak and Gyorgyi
Vitamin concept later dismissed

Low molecular weight polyphenolic substances

Most common group of plant polyphenols (2/3)

Most polyphenol research and health focuses on flavonoids

Ubiquitous: present in most plants

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8
Q

Basic flavonoid structure

A

A ring usually arises from the acetate pathway and usually B ring usually arises from the shikimate pathway

Both A and B rings have OH groups attached (antioxidant potential)

C ring determines the major class of flavonoid (varies)

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9
Q

Flavonoid classification

A

Over 5000 flavonoids have been discovered

Six major subclasses based on variations in C ring
1. Flavones
2. Flavonols
3. Flavanones
4. Flavanols
5. AnthocyaniNS
6. Isoflavones

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10
Q

Flavonoids distribution in plants

A

Located mainly in the leaves, flowers, and outer parts

Decreased concentrations toward the central core

Only trace amounts found in plants below soil surface

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11
Q

Flavonoids in foods

A

Widely distributed in foods and beverages of plant origin (fruits and veggies, tea, cocoa, wine)

Key note is that the amount of flavonoids in foods can vary considerably
- “due to previously mentioned variables like light”

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12
Q

Flavonoid intake

A

Challenges in determining dietary intake related to determination of flavonoid content in plant
- content variation factors include variety, light, crop year, location, ripeness, skin SA

Challenges in determining dietary intake related to Analytical Methodology
- lack of standardization
- lite rupture is inconsistent

Want to optimize health with intake levels

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13
Q

Flavonoid database

A

Inventory of the flavonoid content of foods

Translate dietary assessment data that we collect INTO flavonoid intake levels

USDA Database for the Flavonoid Content of Selected Foods
- 500 foods and 28 different flavonoids
- 5 of 6 subclasses (excludes isoflavones)

Studies can use the flavonoid database to relate intake to health outcomes (eg- flavonoid intake and all cause mortality

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14
Q

Flavonoid glycosides

A

Flavonoids are typically attached/conjugated to a carbohydrate in the food matrix

Terminology reflects if the carbohydrate attachment is there or not
- YES = flavonoid glycoside
- NO = flavonoid aglycone

The majority of flavonoids appear in plants as glycosides
- helps with storage in the plant

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15
Q

Flavonoid bioavailability

A

Initially thought to be negligible since they are bound to glycosides
- it is now known that glycosides can be metabolized to aglycones and absorbed

Important to establish bioavailability before considering impact on health outcomes
- concentrations vary in different biological fluids (urine, blood)

First thing to consider in a phytochemical
- relies on clear knowledge of intake and if absorption occurred therefore need a biological marker of intake
- Intake is best bio marker HOWEVER relationship between dietary intake of flavonoids and biomarkers is complex

Study?

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16
Q

Flavonoid biological effects 1

A

Antioxidant effects
- direct free radical scavenger (OH groups)
- chelate metals involved in initiation of lipid peroxidation, namely iron
- protect vitamin E from oxidation
- regenerates vitamin E that has been oxidized
- increases glutathione levels

17
Q

Flavonoid biological effects 2

A

Hormonal/Anti hormonal effects
- primarily estrogenic and anti estrogenic
- relation to hormone dependent cancers
- isoflavones main flavonoid in this area

18
Q

Flavonoid biological effects 3

A

Anti proliferative
- inhibition of cellular transformation and proliferation
- relevant for existing cancer cells
- inhibit growth of cancer cells in vitro
- interact with enzymes associated with DNA (inhibit DNA topoisomerase ll)

Other biological effects like anti bacterial/viral/fungal etc - all intuitive based on their role in the plant itself

19
Q

Flavonoid health effects

A

Research in reducing risk of diseases like

Major one: Cancer
- antioxidant
- anti estrogenic
- anti proliferative

Major one: cardiovascular disease
- antioxidant
- estrogenic
- anti inflammatory

Other possibilities
- any condition associated with oxidative stress

20
Q

Linking flavonoids and health: key issues

A

Flavonoid content in plants

Flavonoid content of foods
- content variation: analytical methods variation

Flavonoid intake
- dietary assessment: food composition databases
- intake biomarker availability

Flavonoid metabolism
- pharmacokinetics: ADME (absorption, distribution, metabolism, excretion)
- key metabolites not yet identified

Bioavailability influencers (intake amount and absorption)
- all of the above plus food matrix
- contribution of gut microflora

21
Q

Biomarker qualities

A

Sensitive
Specific
Measurable
Cost effective
Feasible
Not invasive
Reference ranges available to refer to