Battle between Antioxidants and Free Radicals

Fat becomes free radicals

http://en.wikipedia.org/wiki/File:Lipid_peroxidation.svg

Initiation

When foods containing unsaturated lipid (LH) enter the body, free radicals (X') steal electrons from the lipids causing lipid peroxidation, the unsaturated fat becomes lipid radical (L').

Propagation

Because lipid radical is not very stable, it readily reacts with oxygen (O2) in the air and becomes peroxyl radical (LOO'). Since this free peroxyl radical is unstable, it continues chain reaction with other free fatty acid.

Termination

When a free radical collides with non-radical, it creates another free radical. When two radicals collide, it creates non-radicals. This only happens when concentration of free radicals is high. Typically, human body has protective mechanisms to speed up termination process by utilizing antioxidants.


There are more than one way that free radicals can form in the body. Some of which are tobacco smoke, radiation, environmental toxins (NO2, HO', etc), alcohol and foods.
Free radicals are extremely reactive, causing lipid, protein, enzymes and DNA damages which contribute to aging, many diseases and cancer.

Green Tea Antioxidants neutralize free radicals and prevent aging, diseases and cancer

Bodily organs and tissues have various defense mechanisms to eliminate free radicals and to repair damages.  Vitamin A, C and E and polyphenols are important antioxidants to neutralize free radicals.  Polyphenol antioxidants are often found in green tea as well as various fruits and vegetables.

Green Tea Antioxidants and EGCg - Effectiveness of green tea antioxidants

Green Tea Antioxidants and EGCg

What is green tea antioxidants and catechins?

Green tea antioxidants are called catechins.  Tea generally contains 11-17% of catechins and they are water soluble.  EGCg or epi-galo-catechin-galate is one of catechins.
Here is each of the green tea catechins % found in green tea.

EG  (0.9%)
EGC  (3.6%)
ECg  (2.2%)
EGCg (7.9%)

*Percentage of each catechin vary depending on cultivation, harvest seasons, harvested leaf type, processing style, and even brewing temperature.  This is an average %.  

Why is green tea antioxidants, especially EGCg, effective in keeping us healthy?

Green tea antioxidants are highly effective antioxidants compared to antioxidants found in other foods.  The table shows that the effectiveness of green tea antioxidants, especially EGCg, is significantly higher than others.  EGCg is 87.5 times more effective than vitamin C and 15 times more effective than BHT (wikipedia link) and BHA (wikipedia link) (These are chemical food additives to keep foods fresh).

	1/IC50(mM)*	ratio
Vitamin C	2.0	1.0
Vitamin E	7.7	3.8
BHT (food additive)	10.3	5.2
BHA (food additive)	11.2	5.6
EC	26.3	12.9
ECg	116.3	57.0
EGC	117.6	57.6
EGCg	178.6	87.5

*half maximal inhibitory concentration (IC50) 

what's IC50? (link wikipedia)
Yoshino et. al. ; Biol Pharm. Bull 17, 146 (1994)

How do green tea antioxidants protect the body from free radicals?

Free radicals are created by various environmental toxins, radiation, foods, tobacco smoke, etc and we are continuously exposed to them.  Once free radicals enter the body, they attack lipids (fat), protein, enzymes, and DNA, which could lead to various ailments and cancer.
Green tea antioxidants suppress these free radical damages by deactivating these free radicals.

Read more; Battle between Antioxidants and Free Radicals



This is a summary from the Japanese Tea Instructor book.