Allyl Sulfur Phytochemicals

Question 1

What are allyl sulfides? Where are they found?

Answer 1

• Organosulfur compounds similar to glucosinolates
• Found in Allium vegetables (garlic, onion, leeks, scallions, chives)
• Reputation in folklore medicine (garlic has rich history of use)

Question 2

What is responsible for the odour in garlic?

Answer 2

Sulfur

Question 3

How are water-soluble sulfur compounds in garlic formed?

Answer 3

Gamma-glutamyl cysteine (water-soluble parent compound) forms:

• SAC (S-allyl Cysteine)
• SAMC (S-allylmercapto Cysteine)

Question 4

How are lipid-soluble sulfur compounds in garlic formed?

Answer 4

• Gamma-glutamyl cysteine forms alliin (lipid-soluble parent compound; stable, sequestered in plant)
• Alliinase (separate from alliin) acts on alliin to form allicin within 6 seconds
• Comes into contact following crushing or chewing of garlic
• Allicin (unstable) forms breakdown products (DAS, DADS, DATS, ajoene) which have biological effects

Question 5

What are the 2 ways allinase is denatured? What is the result and if applicable, the solution?

Answer 5

1. Heat
   - Heat denatures enzyme (this is why heating garlic is associated with decrease in odour)
   - Results in ⟶ less allicin, less DAS/DADS/DATS/Ajoene
   - Solution ⟶ chop/crush garlic and let stand 10 min before cooking
2. Acid
   - Gastric acid will denature allinase (ie. garlic supplements)
   - Less relevance as we don’t often use acid in cooking prior to chopping garlic

Question 6

What are the health benefits of breakdown products? Discuss the uses and if applicable, mechanisms.

Answer 6

1. Immunity (Anti-Microbial)
   - Garlic can be used as antibiotic (decrease in - H. pylori for gastric ulcers, suppress fungal growth, dermatitis)
2. Cancer
   - Increases formation of nitrosothiols; use up available nitrite; less available for synthesis of nitroso compounds (carcinogenic)
   - Inhibit growth of cancer cells
   - Increase activity of Phase II enzymes
3. CVD
   - Improves blood lipids
   - Inhibits platelet aggression (clumping)

Question 7

Discuss bioavailability of garlic.

Answer 7

• Detection of allicin breakdown products in blood/urine have been minimal or none
• PROBLEM: what if allicin is not bioavailable?
• May be detected in the BREATH as a biomarker of intake

Question 8

Discuss garlic supplements; are they bioavailable? What’s the solution?

Answer 8

• Supplements are not chewed and allinase may be denatured from stomach acid
• Low allicin released!
• SOLUTION: enteric-coated pills (acid-resistant cellulose/polyacrylic acid esters that readily dissolve at neutral pH)
• Supplements are standardized for allicin potential (all supplements have allicin!)