Upregulation of erythrocyte ascorbate free radical reductase by tea catechins: Correlation with their antioxidant properties

Tea catechins have been shown to possess a variety of health promoting effects, most of these effects have been attributed to their strong antioxidant property. Ascorbate (ASC) is the primary antioxidant in plasma and human erythrocytes play a vital role in regereneration of ASC in blood plasma by reduction of ascorbate free radical (AFR) into ASC by AFR reductase, a transmembrane enzyme. In the present study we report that tea catechins; EGCG, ECG, EGC and EC driven activation of erythrocyte AFR reductase. The efficiency of tea catechins to activate AFR reductase has a significant positive correlation with the antioxidant activities of these compounds, measured by DPPH scavenging and FRAP assays. Since AFR reductase along with other transmembrane oxidoreductases, is reported to act as compensatory/protective mechanism that operates to minimize the extent of oxidative stress, activation of this enzyme by tea catechins may be a mechanism for these compounds to elicit antioxidant effect in vivo.

► Tea catechins activate ascorbate free radical reductase in erythrocytes.
► Upregulation of AFR reductase is important for ascorbate regeneration in plasma.
► The findings explain the strong antioxidant effect of tea catechins in vivo.