The new study, reported in the 15 March issue of Cancer Research, is one of the first to reveal a mechanism for EGCG's action on cancer, suggesting that the compound binds to the enzyme DHFR, an established target for anticancer drugs.
"There is a lot of information on EGCG and it has been shown that if you treat cancer cells in the lab with it they will die. But although a number of targets have been suggested, no-one has previously managed to explain this action," Professor Roger Thorneley at the UK's John Innes centre told NutraIngredients.com.
The structure of EGCG resembles methotrexate, which kills cancer cells by binding to, and inactivating, the enzyme dihydrofolate reductase (DHFR). The research team found that EGCG also binds strongly to DHFR and stops it functioning.
Dr José Neptuno Rodríguez-López, based at the University of Murcia in Spain, added: "We discovered that EGCG can kill cancer cells in the same way as methotrexate. However, because EGCG binds to the target enzyme less tightly than methotrexate, it should have decreased side effects on healthy cells."
However Professor Thorneley warned that food supplement companies marketing this compound may wish to investigate the impact of such products on pregnant women.
The enzyme DHFR is also involved in folate uptake. If the enzyme is inactivated it could reduce the protection afforded by folate over healthy development of the foetus. A lack of folate has been linked to increased risk of neural tube defects among babies.
"We have not tested this on humans but now that it is known that EGCG compromises folic acid, food supplement firms may wish to investigate this area further," he said.
He added that there is already some epidemiological evidence to show a link between heavy green tea drinking and increased incidence of birth defects.