Effect of green tea on iron status and oxidative stress in iron-loaded rats.

Plasma non-transferrin bound iron (NTBI) is potentially toxic and contributes to the generation of reactive oxygen species (ROS), consequently leading to tissue damage and organ dysfunction. Iron chelators and antioxidants are used for treatment of thalassemia patients. Green tea (GT) contains catechins derivatives that have many biological activities. The purpose of this study was to investigate the iron-chelating and free-radical scavenging capacities of green tea extract in vivo. Rats were injected ip with ferric citrate together with orally administered GT extract (GTE) for 4 months. Blood was collected monthly for measurement of iron overload and oxidative stress indicators. Plasma iron (PI) and total iron-binding capacity (TIBC) were quantified using bathophenanthroline method. Plasma NTBI was assayed with NTA chelation/HPLC. Plasma malonyldialdehyde (MDA) was determined by using the TBARS method. Erythrocyte oxidative stress was assessed using flow cytometry. Levels of PI, TIBC, NTBI and MDA, and erythrocyte ROS increased in the iron-loaded rats. Intervention with GT extract markedly decreased the PI and TIBC concentrations. It also lowered the transferrin saturation and effectively inhibited formation of NTBI. It also decreased the levels of erythrocyte ROS in week 4, 12 and 16. Therefore, green tea extract can decrease iron in plasma as well as eliminate lipid peroxidation in plasma, and destroy formation of erythrocyte ROS in the rats challenged with iron. The bifunctional effects could be beneficial in alleviating the iron and oxidative stress toxicity. In prospective, these GTE activities should be further examined in thalassemic animals or humans.

Epigallocatechin-3-gallate and epicatechin-3-gallate from green tea decrease plasma non-transferrin bound iron and erythrocyte oxidative stress.

Beta-thalassemia patients suffer from secondary iron overload caused by increased iron absorption and multiple blood transfusions. Excessive iron catalyzes free-radical formation, causing oxidative tissue damage. Non-transferrin bound iron (NTBI) detected in thalassemic plasma is highly toxic and chelatable. Desferrioxamine and deferiprone are used to treat the iron overload, but many side effects are found. Epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) in green tea (GT) show strong antioxidant properties. We separated the EGCG and ECG from GT extract using an HPLC, and examined their iron-binding and free-radical scavenging activities. They bound Fe(3+) rapidly to form a complex with a predominant absorption at 560 nm. EGCG and ECG bound chemical Fe(3+) and chelated the NTBI in a time- and dose dependent manner. They also decreased oxidative stress in iron-treated erythrocytes. In conclusion, EGCG and ECG could be natural iron chelators that efficiently decrease the levels of NTBI and free radicals in iron overload.

Effects of the Fenton reagent on transport in yeast.

In the facultatively anaerobic yeast Saccharomyces cerevisiae the uptake rate and the accumulation ratio of 2-aminoisobutyric acid was decreased by some 30% by Fenton's reagent (FR), a powerful source of OH. radicals. Likewise, the uptake of glutamic acid, leucine and arginine was diminished. The mediated diffusion of 6-deoxy-D-glucose was not affected. The H+ symport of maltose and trehalose was inhibited by some 40% both in the initial rate and in the accumulation ratio. FR had a dramatic inhibitory effect when present during preincubation with 50 mmol/L glucose. In the obligately aerobic Lodderomyces elongisporus the uptake of all amino acids tested was decreased by 15-30%, that of 6-deoxy-D-glucose by about 10%. The initial rates of uptake of maltose and trehalose were depressed by FR by 40% and the acceleration of uptake observed after 8 min of incubation, was abolished by FR completely. Acidification rate of the external medium by S. cerevisiae in the presence of glucose or galactose was enhanced three-fold, that after subsequently added K+ was substantially decreased. FR appears to have a dual effect on sugar and amino acid transport processes in yeast: (1) it blocks carrier protein synthesis; (2) it inhibits the source of energy for transport. It does not appreciably affect the carrier proteins themselves.