Flashcards in 21 Glucosinolates Deck (34):
What are glucpsinolates?
Phytochemicals (naturally occurring compounds in plants
- sulfer containing
- Brassica family of plants
- chemically stable
- biologically inactive
Food sources of glucosinolates?
- brussel sprouts
It is important to advance knowledge of phytochemical in relation to ....?
Development of a food composition database for the estimation of ....
Key structural features of glucosinolates
** recognize this structure
Thioglycosidic link (glucose - sulfer - R)
- R ---- SO3- --- O
- usually potassium (cation)
R group of glucosinolate structure is derived from?
- highly variable
- approx. 100 identified
Enzyme type that breaks down glucosinolates
Where are myosinases located?
Within the same plant as glucosinolates, but seperate
What causes myrosinases and glucosinolates to come into contact
tissue damage (caused by pests)
First step of glucosinolate metabolism, cleavage of thioglycosidic bond yields ..
- removes glucose
After thioglycosidic bond has been cleaved from glucosinolate, how does metabolism proceed?
- sulfate released
- several possible breakdown products
- depends on side chain and presence of protein cofactors that modify enzyme action
R ---- N ==== C ==== S isothiocyanate
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
Most researched glucosinolate breakdown products? Why?
- possible anti-cancer effects
3 specific naturally occurring isocyanates
Glucosinolate bioavailability is largely affected by?
food preparation methods
- myrosinase inactivated by cooked (no breakdown products)
What in the body can produce myrosinases?
Can you obtain Glucosinolate breakdown products after cooking brassica veggies?
- colonic bacteria can produce myrosinases
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
Isothiocyanate effect on carcinogen metabolism
- increases body's enzyme defence system against carcinogens
- modulate "balance" between phase I and II enzymes
- in liver and epithilial cells, including colon
What are phase I and II enzymes?
- deal with foreign compounds
- by making them water soluble
First line of defence against carcinogens
Phase I and II enzymes
better to have extra Phase I or phase II enzymes? why?
- phase I makes carcinogenic intermediates worse, but easier for phase II to deal with
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
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
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
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
Isothiocyanates and Cancer (studies)
- inhibition of carcinogenesis
Cell culture studies
- inhibition of cancer cell growth (blocks cell cycle)
- increase apoptosis
What specific metabolite effects estrogen metabolism?
Indole-3-carbonal on estrogen
increase anti-estrogen metabolites
decrease pro-estrogen metabolites
- in urine
- increased ratio of 2/16 hydroxylated estrogen metabolite
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
What can complicate the relationship between glucosinolate and cancer risk?
- affects expression of transcription factors
- ligand binding affinity of receptors
-alter chemopreventative effects
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)
influence of phytochemical on a defined polymorphism