Green tea and bone marrow transplantation: from antioxidant activity to enzymatic and multidrug-resistance modulation

Epigallocatechin-3-gallate (EGCG), the main flavonoid of Green Tea (GT), could play an active role in the prevention of oxidative stress related diseases, such as hematological malignancies. Some effects of EGCG are not imputable to the antioxidant activity, but involve modulation of antioxidant enzymes and uric acid (UA) levels. The latter is the major factor responsible of the plasma Non-Enzymatic Antioxidant Capacity (NEAC). However, hyperuricaemia is a frequent clinical feature caused by tumor lysis syndrome or cyclosporine side effects, before and after bone marrow transplantation (BMT). Besides, food-drug interactions could be associated with GT consumption and could have clinical implications. The molecular mechanisms involved in the redox and drug metabolizing/transporting pathways was discussed with particular reference to the potential role of GT and EGCG in BMT. Moreover, reviewing data on NEAC, isoprostanes, uric acid and various enzymes, from human studies on GT, its extract or EGCG, an increase in NEAC, no effect on isoprostanes and contrasting results on UA and enzymes were observed. Currently, few and contrasting available evidences suggest caution for GT consumption in BMT patients and more studies are needed in order to better understand the potential impact of EGCG on oxidative stress and metabolizing/transporting systems.