THe antioxidant properties of melatonin

Jo Robinson jor at teleport.com
Tue Nov 14 21:17:17 EST 1995


	I believe the most exciting melatonin studies -- and the ones
that have the most relevance to aging -- are those conducted in
the past two years at UTHSC in San Antonio by Russel J. Reiter and his
post-docs.
	In 1993, Reiter and his colleagues made the surprising discovery
that melatonin is not just a potent hormone, it is also an antioxidant.
THis is surprising because no other hormone has been shown to have 
significant antioxidant properties.
	But what is most remarkable is that it now appears that melatonin
is the most potent and universal antioxidant known.
	Unfortunately, I don't know how much the readers of this group
know about free radicals, so I don't know how much detail to include.
Please let me know if I need to backfill.
	There are many theories of aging, but the one with the most
adherents is the free radical theory of aging.  This theory, first proposed
in the 1950s by Denham Harmon (who was recently nominated for the 1995 
Nobel PRize for his efforts), suggests that we age to a large
degree because of damage caused be free radicals, molecules that have an
unpaired electron in the outer orbit.  THis solitary electron forces
a free radical to pirate an electron from another molecule or to dump
its spare electron onto an unsuspecting host.  SInce electrons are
the "glue" that hold a molecule together, molecules that are disrupted
by free radicals suffer considerable damage.  IF these molecules happen
to be essential for the functioning of a cell (they might be in the
DNA molecule, in key proteins, or the membrane lipids, for example) then
the cell can become destroyed or may mutate and become cancerous.
	Antioxidants counter this process.  Melatonin operates by
selflessly donating an electron to  a free radical, sparing a more
vital molecule.
	What makes melatonin so unique -- and so important for our
health and well-being -- are the following factors:
	1.  Melatonin is the most potent antioxidant so far discovered.
It is twice as effective at protecting lipid membranes as vitamin E,
5 times as effective at scavenging a particularly destructive free
radical called the hydroxyl radical as glutathione, and 500 times
as effective at protectin human cells from radiation (a free-radical
generating process) as DMSO.
	["A review of the evidence supporting melatonin's role as an
antioxidant" Reiter, R.J. THe Journal of Pineal Research 1995; 18:1-11.]
	2.  Melatonin crosses the blood-brain barrier with ease.
Melatonin is a small and lipophilic molecule and can traverse the
blood-brain barrier in suficient quantities to protect vital brain
neurons.  It has been argued that free radical damage to neurons is
one of the most destructive part of the aging process.
	
	3.  Melatonin protects every part of the cell, from the membrane
to the DNA molecule inside the nucleus.
	This is not true for other antioxidants. They are limited
to preventing damage either in fatty membranes or the cytosol.
	Melatonin is both fat and water soluble, a rarity in nature.
It's fat-soluble properties are well known.  FOr a discussion of its
in water, see "High melatonin solubility in aqueous medium" J. of
Pineal Research 1994; 16:198-201.)  
	4.  Melatonin offers preferential protection to the DNA molecule.
Melatonin is found in greatest abundance in the nucleus of the cell
where it is closely associated with the DNA molecule.  Numerous
studies have shown that melatonin offers unparalleled protection to
the DNA molecule from free-radical generating substances such as
pesticides, radiation, and carcinogens.
	[Mutation Research 1995; 346:23-31.
	Cancer Letters 1993; 70:65-71
	J. of Pineal Research 1994; 16:198-201]
	5.  Melatonin is not pro-oxidant under any known condition.
Some antioxidants can actually produce free radicals under some
circumstances.  Vitamin C is an example.  When vitamin C is exposed
to free iron, which can happen when tissues are damaged by heat, trauma,
infection, radiation or toxins, it can assist in the creation of 
free radicals.  Melatonin has never been shown to generate free
radicals.

	It is the opinion of Reiter and a number of other researchers
that the gradual loss of melatonin that accompanies the aging process
contributes to the aging process primarily by allowing more free
radical damage to accumulate in key cells.  Taking melatonin supplements
starting in middle age may prevent this age-related acceleration of
free radical damage.  
	But there is yet another way that melatonin may delay the
aging process, and that is by reversing the age-related decline
in immunity.  The subject for the third posting.

	Jo  
	
        Coauthor with Russel Reiter, Ph.D. 
	 of Melatonin: Your Body's Natural Wonder Drug

	For a melatonin FAQ go to http://www.teleport.com/~jor



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|       Jo Robinson		    |            jor at teleport.com             |
|      (503)284-4676                |     2826 NE 18th Portland, OR 97212     | 
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