## 3 Results
### _Trolox Equivalent Antioxidant Capacity of Crude Extract and Selected Enriched OPC Subfractions_  
After the successful characterization of six new OPCs and confirmation of the presence of seven known OPCs from _Aronia melanocarpa_ in _Aronia \(\times\) prunifolia '_Nero'_, four OPCs have been selected to characterize their antioxidant capacity. Furthermore, the antioxidant capacity of the crude extract and quercetin, as a known antioxidant in the literature [25], was analyzed. In the selection process, the highest possible yield of the substances after isolation and a diversity of structures were considered. Subfractions which contain the abundant substances with structures like trimer, tetramer, pentamer and cinchonin trimer (Figure 6 (2) and (5)-(7)), all with a B-type linkage between the (epi)catechin units, were combined for testing antioxidant potential. It has to be mentioned that substances reflect highly enriched fractions from the very complex OPC-rich extract; however, small amounts of other constituents could still be included. But to our best knowledge, data about the antioxidant potential of OPCs in relation to their DP have not been published so far. The subfraction in which \(m/z\) 865 is abundantly present is referred to as \"Subfraction with the main substance trimer \(m/z\) 865\" (SmSTri). SmSTet serves as an abbreviation for the subfraction with the tetramer \(m/z\) 1153 as the main substance. The combined subfraction which contains the pentamer \(m/z\) 1441 as the main substance is labeled SmSPen, and the subfraction with principal substance cinchonin trimer with \(m/z\) 1027 is labeled SmSCin. To characterize the antioxidant capacity, the Trolox equivalent antioxidant capacity assay was used. In order to check the function of the assay, it was carried out with quercetin in addition to the test-substances and the crude extract. For the four OPC subfractions and quercetin, a concentration range of 0.45-11.5 \(\upmu\)M was tested, and for the crude extract a range of 5-100 \(\upmu\)g/mL was tested, and evaluation was restricted to their linear range. The relative inhibition of absorbance at 30 \({}^{\circ}\)C after 6 min of incubation at 734 nm is shown for the enriched subfractions in Figure 7, with the matching inhibition by Trolox in the same plate. The TEAC values were calculated based on their linear regression slope of the relative inhibition of absorbance by the enriched subfractions divided by the corresponding Trolox values as a reference. For all linear regressions, coefficients of determination R\({}^{2}\) > 0.98 were calculated. Figure 6: Confirmed structures of the characterized OPCs in _Aronia \(\times\) prunifolia_ ’Nero’, with the exception of (4). Results for the crude extract and quercetin were calculated in the same manner, with linear regressions and coefficients of determination R\({}^{2}\) > 0.95. These results are presented in Figure 8. All calculated TEAC values are shown in Table 2.  
If a tested compound shows a TEAC value above 1, an antioxidant potential can be postulated. The linear regression slope in the presented plot (Figure 7) as well as the calculated TEAC values (Table 2) show that all the four enriched subfractions exhibit antioxidant capacity. The TEAC value of 0.05 of the crude extract indicates no antioxidant potential. \begin{table}
\begin{tabular}{c c} \hline \hline
**Compound** & **TEAC Value** \\ \hline SmSTri & 2.15 \\ \hline SmSTet & 2.80 \\ \hline SmSPen & 3.82 \\ \hline SmSCin & 2.64 \\ \hline Crude extract & 0.05 \\ \hline Quercetin & 1.12 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Calculated Trolox equivalent antioxidant capacity (TEAC) values of SmSTri, SmSTet, SmSPen, SmSCin, crude extract and quercetin as determined in the TEAC assay. Figure 8: Linear regression plot of the TEAC assay displaying the relative absorbance inhibition through Trolox (white square), quercetin (triangle) and crude extract (circle) with each linear regression. Figure 7: Linear regression plots of the TEAC assay.