Melatonin as an anti-oxidant ?

[Jean]

"(..) what is most remarkable is that it now appears that melatonin
is the most potent and universal antioxidant known"

"Melatonin is the most potent hormone known,in that it has effects
in the picogram range. This is also why it was so late to come to 
researchers attention.  Until the 1980s it was impossible to
measure with accuracy the amount of melatonin in the bloodstream."

"Thus melatonin is irreversibly oxydised and cannot be regenerated
as in the case with some other anti-oxydant"

                                  Jo Robinson
                                   

It seem that melatonin is a potent  anti-oxidant, but what 
is the importance of this hormone as an anti-oxidant in relation to
other anti-oxidant molecules that are in greather aboundance ?

Is melatonin up-regulated by oxidative stress or other reagent 
that stimulate other anti-oxidant ?


Jean Charles