## 4 Discussion
SmSPen shows the highest antioxidant capacity of the tested compounds, followed by SmSTet and SmSTri in consideration of the B-type linked OPCs as a main compound in the tested enriched subfractions. With a B-type pentamer as the main substance, SmSPen features the most hydroxy groups, especially the two hydroxy groups at the B-ring of the individual monomers, which explains the high antioxidant capacity due to the better electron-donating properties [15]. The presence of a further monomer including a vicinal hydroxy group on the B-ring there fore increases the antioxidant effect. This establishes a direct correlation between the DP and the antioxidant effect of the substance. A comparison of SmSTri with SmSCin shows that SmSCin has a higher antioxidant potential than SmSTri. SmSTri contains a B-type trimer as the main substance and SmSCin a B-type cichonain which has two additional vicinal hydroxy groups and thus also forms another radical target, which could explain the slightly higher antioxidant potential of SmSCin. SmSTet and SmSCin exhibit a quite similar TEAC value and contain the same number of ortho-permanent phenolic hydroxy groups per mole, which could explain their similar antioxidant potential. The crude extract on the other hand displays no antioxidant effects. An explanation for this is the fact that although it contains all OPCs, they are present in a significantly lower concentration. The other tested components are highly concentrated for the experiments and therefore show antioxidant capacity. Another explanation could be that interfering substances that are still present in the crude extract hinder the assay. The antioxidant effects of the four tested components and the crude extract previously determined in the cell-free TEAC assay, were subsequently investigated in vitro. The analysis at a cellular level also takes into account all cell culture conditions that could have an influence on the antioxidant properties of the compounds. The modified DCFH\({}_{2}\)-DA assay was chosen because it allows a precise analysis of the antioxidant capacity in vitro and is well adapted to the culture conditions and protocols and has been published in the literature for similar experiments [24; 31]. The results (Figure 9) show intracellular concentration-dependent antioxidant capacity for SmSTri most clearly after a short period of peroxide incubation. However, the concentration-dependent effect is also noticeable over the entire time of the measurement. SmSTet displays these effects comparable to SmSTri. SmSPen shows notable effects only at the lowest concentrations used. At all other concentrations and time points, no intracellular antioxidant effects were observed; SmSPen therefore shows no concentration-dependent antioxidant effect compared to the other components investigated. With SmSCin, however, observable effects only occur at the higher concentration of 10 uM and 20 uM and at the later points in time of measurement. For the other concentrations and points in time, however, no intercellular antioxidant capacity can be observed, except for the first time point of 15 min after peroxide incubation. Although SmSTri and SmSCin each have trimeric OPCs as main substances, the phenylpropanol moiety of the cichonain appears to have a marked effect on intracellular antioxidant capacity and/or on the cellular uptake of this substance. The previous generated TEAC assay results show the antioxidant capacity in the following order: SmSPen > SmSTet > SmSCin > SmSTri. This discrepancy in comparison to the previously determined results from the TEAC assay can be an indication that the substances are not or are only in low concentrations taken up intracellularly due to their size or that they are not stable throughout the duration under cell culture conditions. Assuming that the OPCs with a higher DP degrade under the cell culture conditions, individual effects can be explained by the fact that the smaller degradation products can pass the cell membrane and thus act intracellularly as ROS scavengers.