Hypoxia occurs when oxygen supply to tissue or the whole body is restricted. If cells are denied oxygen for too long they die, a process called apoptosis. The most well known form of hypoxia is altitude sickness, which can occur when travellers go above an altitude of 1,829 to 2,438m.
"Hypoxia is known to have an important role in a number of pathophysiological process, including wound healing, cardiovascular-related disease and cancer," explained lead author Hae Jeong Park from the Kyung Hee University in Seoul.
EGCG has been linked to a variety of health benefits including protection against Alzheimer's and certain cancers. However, the FDA recently released a report that said the anti-cancer effects of green tea were 'highly unlikely'.
In the new study, published on-line in the journal Life Sciences (doi: 10.1016/j.lfs.2005.11.001), looked at the effect of EGCG on hypoxia-induced apoptosis for human haematoma cells.
Cells were exposed to varying concentrations of the tea extract (12.5, 25, 50, 100 micromoles) and the number of live cells tested.
In the control cell culture, 40 per cent of cells died due to lack of oxygen. In the test groups though cell death was decreased for all EGCG concentrations. Exposure to 12.5 micromoles of EGCG reduced cell death by 10 per cent, while all cells were still alive in after exposure to 100 micromoles of EGCG.
The mechanism was proposed to be due to EGCG preventing the expression of a certain enzyme called caspase 3, which plays a important role in programmed cell death.
"EGCG markedly inhibited the apoptosis by hypoxia; it contributed to the haematoma cells survival by attenuating hypoxia-induced apoptosis," concluded Park.
European demand for tea extracts is currently surging, having reached 500 metric tonnes by 2003.
This has seen companies such as DSM, with its Teavigo boasting 95 per cent purity of EGCG, and Taiyo International, with its Sunphenon claiming more than 90 per cent purity, position themselves firmly in specific catechin markets.
The global tea market is worth about €790 (£540, $941) million. Green tea accounts for about 20 per cent of total global production, while black tea (green tea that has been oxidized by fermentation) accounts for about 78 per cent.