Figure 4.

Effect of phenolic acids on the inhibition of H₂O₂ cytotoxicity. (a) Cells (15 × 10⁴) were incubated for 24 hours with the different phenolic acids (10^-7 M). The medium was then discarded and replaced with a fresh one, in which fetal bovine serum was omitted, containing the indicated concentrations of H₂O₂. Incubation was followed for 3 hours, and then the viability of cells was determined by the MTT method. Results are presented of an experiment (in triplicate) performed four times with similar results. (b) The difference of effective concentration 50% values of H₂O₂ obtained in the presence of phenolic acids, as compared with control experiments. Bars represent the standard error of the mean of four different experiments performed in triplicate. IC₅₀, inhibitory concentration 50%; PAA, 3,4-dihydroxy-phenylacetic acid.