Spanish and British scientists have
discovered how green tea helps to prevent certain types of
Researchers at the University
of Murcia in Spain (UMU) and the John Innes Center (JIC) in
Norwich, England have shown that a compound called EGCG in
green tea prevents cancer cells from growing by binding to
a specific enzyme.
"We have shown for the first
time that EGCG, which is present in green tea at relatively
high concentrations, inhibits the enzyme dihydrofolate reductase
(DHFR), which is a recognized, established target for anti-cancer
drugs, " Professor Roger Thorneley, of JIC, stated.
"This is the first time, to
our knowledge, a known target for an anti-cancer drug has
been identified as being inhibited by EGCG," he added.
Green tea has about five times
as much EGCG as regular tea, studies have shown. It decreased
rates of certain cancers but scientists were not sure what
compounds were involved or how they worked. Nor had they determined
how much green tea a person would have to drink to have a
beneficial effect, he said.
Thorneley said EGCG is probably
just one of a number of anti-cancer mechanisms in green tea.
"We have identified this enzyme
in tumour cells that EGCG targets and understand how it stops
this enzyme from making DNA. This means we may be able to
develop new anti-cancer drugs based on the structure of the
EGCG molecule," Thorneley explained.
The scientists decided to look
at ECGC after they realized its structure was similar to a
cancer drug called methotrexate.
"We discovered that EGCG can
kill cancer cells in the same way as methotrexate," Dr Jose
Neptuno Rodriguez-Lopez, of UMU, a joint author of the research
published in the journal Cancer Research.
EGCG binds strongly to DHFR,
which is essential in both healthy and cancerous cells. But
it does not bind as tightly as methotrexate, so its side effects
on healthy cells could be less severe than those of the drug.
Thorneley said EGCG could be
a lead compound for new anti-cancer drugs.
The findings could also explain
why women who drink large amounts of green tea around the
time they conceive and early in their pregnancy may have an
increased risk of having a child with spina bifida or other
neural tube disorders.
Women are advised to take supplements
of folic acid because it protects against spina bifida. But
large amounts of green tea could decrease the effectiveness
of folic acid.
"This enzyme, (DHFR), is the
one folic acid supplements are given for. Folic acid deficiency
leads to neural tube development defects," Thorneley added.