Distribution of betalain pigments in red blood cells after consuption of cactus pear fruits and increased resistance of the cells to ex vivo induced oxidative hemolysis in humans

Betalain pigments are bioavailable phytochemicals recently acknowledged as natural radical scavengers. This work, which extends previous research on the postabsorbitive fate of dietary betalains, investigated the distribution of betanin and indicaxanthin in red blood cells (RBCs) isolated from healthy volunteers (n ) 8), before and during the 1-8 h interval after a cactus pear fruit meal, and the potential antioxidative activity of the pigments in these cells. A peak concentration of indicaxanthin (1.03 ( 0.2 íM) was observed in RBCs isolated at 3 h after fruit feeding, whereas the concentration at 5 h was about half, and even smaller amounts were measured at 8 h. Indicaxanthin was not detected at 1 h. Betanin (30.0 ( 5.2 nM) was found only in RBCs isolated at 3 h from fruit feeding. In comparison with homologous RBCs before fruit ingestion, a significant delay (P < 0.05) of the onset of an ex vivo cumene hydroperoxide (cumOOH)-induced hemolysis was evident in the RBCs isolated at 3 h (33.0 ( 4.5 min) and at 5 h (16.0 ( 2.0 min). Neither vitamins C and E nor GSH was modified in the RBCs at any time point. Blood collected from the same volunteers after a 12-h fasting was incubated with the purified betalains in the range of 5-25 íM, to enrich the erythrocytes with either betanin or indicaxanthin, and then the cells were exposed to cumOOH. When compared to the relevant nonenriched cells, the betalain-enriched erythrocytes exhibited an enhanced resistance to the cumOOH-induced hemolysis, which was positively correlated (r 2 ) 0.99) to the amount of the incorporated compound. On a micromolar basis, betanin and indicaxanthin showed a comparable effectiveness. Taken together, these findings provide evidence that human RBCs incorporate dietary betalains and support the concept that these phytochemicals may offer antioxidative protection to the cells.