*3.2. Cytotoxicity Studies*

Both cell types exposed to the extract underwent a concentration and time-dependent decrease in all endpoints. In HepG2 cells, after 24 h of exposure, the MTS assay indicated a significant reduction in the cellular viability at concentrations of 40 μg/mL and above, showing greater alteration than the TP and NR assays (Figure 1A). Similarly, the most sensitive endpoints after 48 h were MTS reduction and NR uptake (Figure 1B). Considering the EC50 values, toxic effects were more evident in HepG2 cells in the longer exposure time, being 31.2 ± 2.4 μg/mL for 24 h, and 20.6 ±2.7 μg/mL for 48 h of exposure.

**Figure 1.** Reduction of tetrazolium salt (MTS), neutral rep uptake (NR), and total protein content (TP) of HepG2 cells exposed for 24 h (**A**) and 48 h (**B**) to 0–100 μg/mL of the stilbene extract (45%). All values expressed as mean ± SD. Significant differences in respect to the control from *p* < 0.01 (\*\*).

After the exposure of Caco-2 cells to the extract, all assays showed similar concentration-dependent reduction in cell viability. MTS assay indicated a marked reduction in the cellular viability, being the EC50 value in this endpoint of 55.8 ± 4.0 μg/mL and 39.0 ± 2.7 μg/mL after 24 h and 48 h, respectively. These decreases were significantly different from the control group at the concentration 40 μg/mL and above at 24h, but when cells were exposed to the extract for two days, the cell viability was significantly reduced from 30 μg/mL (Figure 2).

**Figure 2.** Reduction of tetrazolium salt (MTS), neutral rep uptake (NR), and total protein content (TP) of Caco-2 cells exposed for 24 h (**A**) and 48 h (**B**) to 0–100 μg/mL of the stilbene extract (45%). All values expressed as mean ± SD. Significant differences in respect to the control from *p* < 0.05 (\*) and *p* < 0.01 (\*\*).
