FIG 6 .

Influence of T4C, MT4C, and l-cysteine on the intracellular ROS levels. Trophozoites were cultivated in l-cysteine-deprived BI-S-33 medium for 72 h, and after that, the medium was replaced with l-cysteine-deprived BI-S-33 media containing 2 mM T4C, MT4C, or l-cysteine. After 3 h, approximately 4.0 × 10⁵ cells were then incubated with the dye 2′,7′-DCF-DA for 20 min. The intracellular ROS levels were quantified by determination of DCF fluorescence. Results were normalized with cell numbers and are presented relative to levels in untreated control cells. The means ± SD from three independent experiments performed in triplicate are shown. Statistical comparisons were made by Student’s t test (**, P < 0.01; ***, P < 0.001).