Free Radicals, Antioxidants and Revolutionary Noninvasive Antioxidants Testing.
Antioxidants and phytochemical talk 05 07-11
-
Upload
mjklin -
Category
Health & Medicine
-
view
2.249 -
download
0
Transcript of Antioxidants and phytochemical talk 05 07-11
![Page 1: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/1.jpg)
Phytochemicals
John Parry, Ph.D.
Rm 229, M.T. Carter Bldg
Agricultural Research Station
Phone: (804) 524-5957
Email: [email protected]
![Page 2: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/2.jpg)
Tocopherols (Vitamin E)• Eight vitamers:• ( ) tocopherol• ( ) tocotrienol• Prevent peroxyl radical propagation in lipids• The most conserved is -tocopherol• Found mainly in oils (wheat germ, corn)
![Page 3: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/3.jpg)
Carotenoids
• Include: -carotene
• They are not direct antioxidants– They quench the energy of singlet O2 which is more
reactive than triplet O2
• Some carotenoids can be converted to vit. A
• Orange colored foods– They were found to be very high in pumpkin seeds
in a previous study, carrots, and sweet potatoes.
![Page 4: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/4.jpg)
Essential Fatty Acids
• Linoleic acid (18:2n6)
• Linolenic acid (18:3n3)
• DHA (22:6n3)
• EPA (20:5n3)
• Some of these can be found in plant foods such as flax seed oil, basil seed oil, cold water fish
• Other sources:
![Page 5: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/5.jpg)
Phytosterols
-sitosterol, -7 avenosterol, stigmasterol, etc.
• These molecules resemble cholesterol and have been shown to decrease cholesterol levels
![Page 6: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/6.jpg)
Phenolic Antioxidants
• Phenolic compounds have been shown to have antioxidant properties in vitro when compared vitamin E and C
• The French Paradox– Initially the bioflavonoid content was the reason
• Recently resveratrol has been suggested as the reason for the paradox
![Page 7: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/7.jpg)
Phenolic Antioxidants
• Are gradually losing popularity among scientist in the field while still publically demanded
• Jeff Moore
![Page 8: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/8.jpg)
Free Radicals
• Biologically relevant free radicals:– Superoxide anion – O2
_
– Hydroxyl – OH (very reactive)
– H2O2 – not a free radical but very reactive
– Peroxyl – ROO
![Page 9: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/9.jpg)
Enzymatic Antioxidants• Superoxide dismutase – 2O2
_ O2 + H2O2
Group of isozymes Kcat (turnover rate) 1 x 107 per second
• Catalase – H2O2 2 H2O + O2
• Kcat 1 x 106 per second
• Glutathione peroxidase – LOO LOH Group of isozymes
![Page 10: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/10.jpg)
Free Radicals• Other biologically relevant damaging
molecules related to free radicals:
–Hydrogen peroxide – H2O2
– Fenton reaction• Fe (II) + H2O2 Fe (III) + OH_+ OH
– Peroxynitrite – ONOO _
• Formed by the reaction of nitrite and O2 _
• Reacts with CO2 forming a CO3 , and NO2
– Peroxynitrous acid – ONOOH (pKa ~ 6.8)• Forms OH and NO2
![Page 11: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/11.jpg)
Antioxidants: Synthesized1. BHA – Butylated hydroxy anisole2. BHT – Butylated hydroxy toluene3. TBHQ – tert-Butylhydroxyquinone• All 3 of these are lipophilic (fat soluble)• These are added to foods to protect susceptible
fatty acids and fat soluble vitamins
Health concerns regarding synthesized antioxidants:• cause cancer in animal studies• damage DNA
![Page 12: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/12.jpg)
Enzymatic Antioxidants• Superoxide dismutase – 2O2
_ O2 + H2O2
• Catalase – H2O2 2 H2O + O2 (Kcat 1 x 107)
• Glutathione peroxidase – LOO LOH
• These enzymes and enzyme systems are continually operating but genetic expression is upregulated during oxidative stress
![Page 13: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/13.jpg)
Antioxidants: Non-Enzymatic
• Ascorbic Acid• Tocopherols (8 isoforms)• Carotenoids• Phenols and Polyphenols (found in plants)• Glutathione• Lipoic acid (a fatty acid with disulfide antioxidant)• Coenzyme Q (involved in electron transport chain)• Melatonin (• Bilirubin (a breakdown product of red blood cells)• Uric acid
![Page 14: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/14.jpg)
Antioxidants: Non-Enzymatic
• Tocopherols (8 isoforms) -, -, -, -Tocopherol -, -, -, - Tocotrienol
-Tocopherol
-Tocotrienol
![Page 15: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/15.jpg)
Antioxidants: Non-Enzymatic
• Vitamin E (-Tocopherol) is the most effective antioxidant of the 8 isoforms– Vitamin E protects lipid membranes from
oxidation of unsaturated fatty acids• Most susceptible tissues:
– It is stored in lipid membranes, adipose tissue liver, heart, muscle, and adrenal glands
– It is thought to be regenerated by vitamin C
![Page 16: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/16.jpg)
Antioxidants: Non-Enzymatic• Vitamin A and Carotenoids
• Beta carotene has 2 beta ionone ring making it capable of forming 2 vitamin A molecules
![Page 17: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/17.jpg)
Antioxidants: Non-Enzymatic• Over 700 carotenoids have been identified
comprised of 2 structural groups1. Some hydrocarbon carotenes
-carotene -carotene (1 vitamin A; has one ionone ring)– Lycopene
2. Some oxygenated xanthophylls -cryptoxanthin– Lutein– Zeaxanthin (corn)
The mechanism of antioxidant protection from the carotenoids is not from free radical scavenging but from the quenching of singlet oxygen (1O2)
![Page 18: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/18.jpg)
Antioxidants: Non-Enzymatic
• Glutathione
– (GSH) – reduced form (90%)– (GSSG) – oxidized form (10%)– Consists of gly, cys, and glu– Thiol group is active– Used by glutathione peroxidase to reduce
peroxides
![Page 19: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/19.jpg)
Antioxidants: Non-Enzymatic
• Glutathione– Can reduce the oxidized form of vitamin E– Is made in every cell of the body but primarily
the liver– Glutathione reductase is continually active and
is inducible when subjected to oxidative stress– NADPH can reduce GSSG to GSH
![Page 20: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/20.jpg)
Antioxidants: Non-Enzymatic
• Phenolic compounds– Exist in virtually all plant foods– Very highly concentrated in spices
• Phenolic acids• Gallic acid, syringic acid, p-OH benzoic acid, vanillic
acid
• Hydroxycinnamic acids• Ferulic acid, p-coumaric acid, caffeic acid
• Polyphenolic acids• Anthocyanins, proanthocyanins
![Page 21: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/21.jpg)
Antioxidant
Basic Phenol Radical Resonance for Stability
OH O O O O O
-H
+H
![Page 22: Antioxidants and phytochemical talk 05 07-11](https://reader035.fdocuments.us/reader035/viewer/2022070313/554aaf5ab4c905df668b53a8/html5/thumbnails/22.jpg)
Phenolic Antioxidants
O
CH3
HO
O
OH
ferulic acid
OH
OH
HO O
OH
catechin
Fe++HO