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Nutrition 3330 > 21 Glucosinolates > Flashcards

21 Glucosinolates Flashcards

1
Q

What are glucpsinolates?

A

Phytochemicals (naturally occurring compounds in plants

  • sulfer containing
  • Brassica family of plants
  • chemically stable
  • biologically inactive
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2
Q

Food sources of glucosinolates?

A 
Cruciferous veggies
Brassica family
- broccoli
- cabbage
- brussel sprouts
- cauliflower
- Kale
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3
Q

It is important to advance knowledge of phytochemical in relation to ….?

A

disease risk

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4
Q

Development of a food composition database for the estimation of ….

A

Dietary Intakes

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5
Q

Key structural features of glucosinolates

** recognize this structure

A

Thioglycosidic link (glucose - sulfer - R)

Sulfate Group

  • R —- SO3- — O
  • usually potassium (cation)
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6
Q

R group of glucosinolate structure is derived from?

A

amino acids

  • highly variable
  • approx. 100 identified
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7
Q

Enzyme type that breaks down glucosinolates

A

Myosinases

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8
Q

Where are myosinases located?

A

Within the same plant as glucosinolates, but seperate

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9
Q

What causes myrosinases and glucosinolates to come into contact

A

tissue damage (caused by pests)
harvesting
food processing
chewing

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10
Q

First step of glucosinolate metabolism, cleavage of thioglycosidic bond yields ..

A

Algycone

- removes glucose

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11
Q

After thioglycosidic bond has been cleaved from glucosinolate, how does metabolism proceed?

A 
becomes unstable
degrades spontaneously
non-enzymatic rearrangment
- sulfate released
- several possible breakdown products
- depends on side chain and presence of protein cofactors that modify enzyme action

R —- N ==== C ==== S isothiocyanate

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12
Q

Possible effects of glucosinolate breakdown products

A
  • possible toxicological effects
  • plant defence system (insects, fungi, etc)
  • bitter taste in condements
  • characteristic flower of numerous veggies
  • ** potential anti-carcinogenic effect in humans
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13
Q

Most researched glucosinolate breakdown products? Why?

A

Isothiocyanates

- possible anti-cancer effects

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14
Q

3 specific naturally occurring isocyanates

A

PEITC
BITC
Sulforaphane

(broccoli) ?

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15
Q

Glucosinolate bioavailability is largely affected by?

A

food preparation methods

- myrosinase inactivated by cooked (no breakdown products)

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16
Q

What in the body can produce myrosinases?

A

Colonic Bacteria

17
Q

Can you obtain Glucosinolate breakdown products after cooking brassica veggies?

A

yes

- colonic bacteria can produce myrosinases

18
Q

Fresh vs Steamed broccoli study

- difference in urine/blood concentrations of isothiocyanate?

A

Fresh 3x higher isocyanate concentration than steamed

  • some still in steamed
  • hydrolysis of Glucosinolate likely by intestinal microflora
19
Q

Isothiocyanate effect on carcinogen metabolism

A

chemoprotection

  • increases body’s enzyme defence system against carcinogens
  • modulate “balance” between phase I and II enzymes
  • in liver and epithilial cells, including colon
20
Q

What are phase I and II enzymes?

A

Metabolize xenobiotics
biotransformation enzymes
- deal with foreign compounds
- by making them water soluble

21
Q

First line of defence against carcinogens

A

Phase I and II enzymes

22
Q

better to have extra Phase I or phase II enzymes? why?

A

Phase II

- phase I makes carcinogenic intermediates worse, but easier for phase II to deal with

23
Q

Phase I enzymes method

A

known as “activation enzymes” (ex. Cytochrome P-450 family)

  • oxidation, reduction and hydrolysis reactions
  • metabolize lipophilic pro-carcinogens
  • make them “water soluble”
  • allows phase II to act on them
24
Q

Phase II enzymes method

A

“detoxification enzymes” (ex. GST glutathoine transferase family)

  • metabolize phase I generated epoxides
  • form inactive water soluble conjugates
  • readily excreted in urine

also metabolize free radicals to inactive metabolites

25
Q

Can diet modulate Phase I and II enzymes?

A

Glucosinolate breakdown products “increase” phase II enzymes (glutathione transferases)

  • no effect on phase I
  • want more II than I
26
Q

5 mechanisms glucosinolate breakdown products protect against cancer

A
  1. modulation phase I and II enzymes
    - increase phase II
  2. indirect anti-oxidant effects
    - phase II metabolize free radicals
  3. Induces apoptosis
    - independent of enzymes
  4. Blocks cell cycle
  5. Modifier of “Estrogen” Metabolism
27
Q

Isothiocyanates and Cancer (studies)

A

Animal Studies
- inhibition of carcinogenesis

Cell culture studies

  • inhibition of cancer cell growth (blocks cell cycle)
  • increase apoptosis
28
Q

What specific metabolite effects estrogen metabolism?

A

Indole-3-carbinol

29
Q

Indole-3-carbonal on estrogen

A

increase anti-estrogen metabolites
decrease pro-estrogen metabolites
- in urine
- increased ratio of 2/16 hydroxylated estrogen metabolite

30
Q

2/16 hydroxylated

A

used as a biomarker in studies evaluating the cancer-protective effects of an intervention

  • higher = lower risk cancer
  • indole-3-carbonal increases this to estrogen metabolite ratio
31
Q

What can complicate the relationship between glucosinolate and cancer risk?

A

Genetic polymorphisms

  • affects expression of transcription factors
  • ligand binding affinity of receptors
  • alter chemopreventative effects
32
Q

Genetic Polymorphisms

A

individual differences in cancer risk in response to cruciferous veggies exposure
- secondary to genetic and associated functional variations in biotransformation enzymes

Studied: GST (phase II)

33
Q

Interaction

A

influence of phytochemical on a defined polymorphism

34
Q

Broccosprouts

A

20x the sulforaphane-glucosinolate (SG) than broccoli

  • tested 50 different kinds of broccoli seeds
  • found one that yielded sprouts with highest and most consistent glucosinolate levels

Nutrition 3330 (22 decks)

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