Effect of naringenin (NRG), ASME, quercetin (QUER), marrubiin (MARR), and curcumin (CURC) on the water permeability of HeLa cells in normal and heat-stress conditions. HeLa cells were exposed to a 150 mOsm osmotic gradient in four different conditions: (1) untreated cells (Controls, Ctr); (2) cells treated at 42 °C for 3 h (heat-stressed, Heat); (3) heat-stressed cells pre-treated with the antioxidants compounds (NRG, ASME, QUER, MARR, CURC pre); (4) heat-stressed cells post-treated with the antioxidants compounds (NRG, ASME, QUER, MARR, CURC post). The effect of NRG, ASME, QUER, MARR, CURC on water permeability independently on their antioxidant properties was measured in HeLa cells treated at 21 °C for 3 h with single compounds at 20 µM final concentration. Bars represent the osmotic water permeability of HeLa cells expressed as k relative. Values are means ± SEM of 4–15 single shots for each of 4–6 different experiments. NRG, ASME, QUER and MARR: * p < 0.05 vs. Ctr, pre and post (ANOVA for repeated measures, followed by Newman–Keuls’ Q test). CURC: * p < 0.05 vs. Heat, pre and post; ° p < 0.05 vs. pre and post (ANOVA for repeated measures, followed by Newman–Keuls’ Q test). CONTROLS: * p < 0.05 vs. vehicle (ANOVA followed by Dunnett t test).