Fig. 1.

Influences of ellagic acid and urolithin A on the ATRA-induced O₂⁻-generating activity in U937 cells. (A) Conversion scheme of ellagic acid to urolithin A by intestinal bacteria. (B) Influences of ATRA plus ellagic acid or urolithin A on induction of the O₂⁻-generating activity. O₂⁻ generation was determined after culture of the cells at 37 °C for 48 h in the absence (None) or presence of each agent (ATRA, ATRA plus ellagic acid or ATRA plus urolithin A) as in “Materials and methods.” Cells (1 × 10⁶ cells/ml) were stimulated with 200 ng/ml PMA at 37 °C. PMA-induced chemiluminescences were measured at 10 min after stimulation. Data represent the averages of three separate experiments and error bars indicate standard deviation. **, P < 0.01 compared with the data of ATRA-treated cells; n. s., not significant.