Midterm 3 (Lecture 12) Flashcards
Phytochemicals
Non nutritive Substances found in plants
Proposed to contribute toward disease prevention
> 900 classes
Examples: alicia in garlic
Flavonoids
Phytoestrogens
Catechins
Lycopene
Plant polyphenols
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
Plant polyphenol classes
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
What influences amount of polyphenols in plants
- light
- genetic factors
- environmental conditions
- ripeness
- variety
- processing, storage
Polyphenols in food
Contribute toward the sensory qualities
- bitterness
- Astringency
- colour
- flavour
- door
- oxidative stability
Polyphenols as anti nutrients
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
Flavonoids
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
Basic flavonoid structure
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)
Flavonoid classification
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
Flavonoids distribution in plants
Located mainly in the leaves, flowers, and outer parts
Decreased concentrations toward the central core
Only trace amounts found in plants below soil surface
Flavonoids in foods
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”
Flavonoid intake
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
Flavonoid database
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
Flavonoid glycosides
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
Flavonoid bioavailability
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?
