21 Glucosinolates Flashcards Preview

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Flashcards in 21 Glucosinolates Deck (34):
1

What are glucpsinolates?

Phytochemicals (naturally occurring compounds in plants
- sulfer containing
- Brassica family of plants
- chemically stable
- biologically inactive

2

Food sources of glucosinolates?

Cruciferous veggies
Brassica family
- broccoli
- cabbage
- brussel sprouts
- cauliflower
- Kale

3

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

disease risk

4

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

Dietary Intakes

5

Key structural features of glucosinolates
** recognize this structure

Thioglycosidic link (glucose - sulfer - R)

Sulfate Group
- R ---- SO3- --- O
- usually potassium (cation)

6

R group of glucosinolate structure is derived from?

amino acids
- highly variable
- approx. 100 identified

7

Enzyme type that breaks down glucosinolates

Myosinases

8

Where are myosinases located?

Within the same plant as glucosinolates, but seperate

9

What causes myrosinases and glucosinolates to come into contact

tissue damage (caused by pests)
harvesting
food processing
chewing

10

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

Algycone
- removes glucose

11

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

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

12

Possible effects of glucosinolate breakdown products

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

13

Most researched glucosinolate breakdown products? Why?

Isothiocyanates
- possible anti-cancer effects

14

3 specific naturally occurring isocyanates

PEITC
BITC
Sulforaphane

(broccoli) ?

15

Glucosinolate bioavailability is largely affected by?

food preparation methods
- myrosinase inactivated by cooked (no breakdown products)

16

What in the body can produce myrosinases?

Colonic Bacteria

17

Can you obtain Glucosinolate breakdown products after cooking brassica veggies?

yes
- colonic bacteria can produce myrosinases

18

Fresh vs Steamed broccoli study
- difference in urine/blood concentrations of isothiocyanate?

Fresh 3x higher isocyanate concentration than steamed

- some still in steamed
- hydrolysis of Glucosinolate likely by intestinal microflora

19

Isothiocyanate effect on carcinogen metabolism

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

What are phase I and II enzymes?

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

21

First line of defence against carcinogens

Phase I and II enzymes

22

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

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

23

Phase I enzymes method

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

Phase II enzymes method

"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

Can diet modulate Phase I and II enzymes?

Glucosinolate breakdown products "increase" phase II enzymes (glutathione transferases)
- no effect on phase I
- want more II than I

26

5 mechanisms glucosinolate breakdown products protect against cancer

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

Isothiocyanates and Cancer (studies)

Animal Studies
- inhibition of carcinogenesis

Cell culture studies
- inhibition of cancer cell growth (blocks cell cycle)
- increase apoptosis

28

What specific metabolite effects estrogen metabolism?

Indole-3-carbinol

29

Indole-3-carbonal on estrogen

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

30

2/16 hydroxylated

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

What can complicate the relationship between glucosinolate and cancer risk?

Genetic polymorphisms
- affects expression of transcription factors
- ligand binding affinity of receptors
-alter chemopreventative effects

32

Genetic Polymorphisms

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

Interaction

influence of phytochemical on a defined polymorphism

34

Broccosprouts

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