Green-tea chemical offers hope of HIV drug

Wed Apr 11, 6:09 PM
ET

SUMMARY: A chemical in green
tea
reduces HIV’s ability to infect cells, say scientists hoping to
emulate the story of a drug developed after a study of green coffee
beans.

Scientists in Texas and the U.K. have found
that a chemical from green tea reduces HIV’s ability to infect
cells.

The scientists from the
University of Sheffield and Baylor College of Medicine in Houston found that as
little as two cups of green tea could provide enough of the chemical
epigallocatechin gallate (EGCG) to inhibit HIV cell binding by 40 per
cent.

However, they do not recommend
that people start drinking gallons of green tea as an HIV preventative. Rather,
they are conducting research to find out if EGCG or a chemical like it would
make a good HIV
drug.

Epigallocatechin gallate is a
catechin, one of a large family of chemicals called bioflavonoids that are found
in tea, red wine and many fruit and vegetables. Most are colored red or purple
and/or taste bitter; many have antioxidant properties and have been investigated
for some time as possible anti-cancer and cardiovascular
drugs.

Baylor’s Dr. Christina Nance
and her team found that EGCG exerts a more direct effect on HIV infection. The
molecule likes to bind to CD4, the cell-surface molecule which HIV first binds
to as well.

This was discovered by
Japanese scientists in 2003, but by using computers to image the exact shape of
the proteins and working out the electronic processes involved, Nance’s team
worked out that ECGC sticks to exactly the same amino acid (component) of the
CD4 molecule as gp120 — the “docking module” of HIV —
does.

“When it binds there, the
gp120 envelope protein, and thus HIV, can’t,” Nance
said.

Her team’s findings are
published in a recent issue of the Journal of Allergy and Clinical
Immunology.

The history of HIV
medicine is full of promising-looking compounds from plants that had some effect
on the HIV virus in the test tube but, when tested in animals and humans, either
produced no effect or only did so at toxic doses. The previous Japanese research
had indicated that the same would be true of EGCG — huge doses would be
needed.

But Nance said that
“physiological levels” of EGCG — that is, 0.2 micromols per liter, or the
amount in just a cup or two of green tea — inhibited HIV binding by 40
percent.

The team is now using
computer-imaging tools to examine more closely the way that EGCG binds to CD4 in
the hope of developing improved molecules that will bind to it more
closely.

It is also investigating
the possibility of a small trial of ECGC in humans to see if it blocks HIV
infection in real life.

If EGCG or
something like it does lead to an HIV treatment, it won’t be a first. The story
of the integrase inhibitors, which has now finally resulted in the launch of a
new drug, raltegravir, started when researchers looked as substances from green
coffee beans.

And another drug now
undergoing trials, bevirimat, was derived from chemicals found in birch-tree
bark.

Will a mug of English
Breakfast have the same effect? No. Black tea leaves contain EGCG, but in much
lower quantities. That’s because black tea leaves are fermented, during which
process many of the cathechins are oxidized to darker-colored molecules called
theaflavin and thearubigen. (Gus Cairns, Gay.com U.K.) If you’d like to know
more, you can find stories related to Green-tea chemical offers hope of HIV drug
.


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Posted: 04/12/2007 at 08:22 AM
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Posted: 04/12/2007 at 08:22 AM
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