## 4 Discussion  
Complex food extracts rich in secondary plant metabolites are widely used as food supplements offering antioxidant properties; however, the knowledge about the contribution of larger oligomeric structures to the suggested bioactivity is quite limited so far. Based on the different linkage types and the various monomer units, OPCs display a wide variety of structures. Structural diversity of this substance group strongly increases with an enhanced degree of polymerization. Overall, in this study, 58 analytes were identified in the crude extract which was generated from chokeberry pomace of the variety _Aronia_\(\times\)_prunifolia_ 'Nero' via high-resolution mass spectrometry. Including five trimers, four tetramers, two pentamers, one hexamer and one dimer of interest as well as several isomers of those. Besides the trimer with an A-type linkage and a gallocatechin unit (\(m/z\) 879) which was already described by [PERSON] et al., a tetramer (\(m/z\) 1167) with the described structural features could also be characterized by its fragmentation spectrum. In addition to the A-type and B-type OPCs, the so-called cinchonains were identified as dimer, trimer, tetramer and pentamer, whereby only the trimer was described in detail in the literature [11]. Consequently, three further cinchonains could be characterized in chokeberries. The characterized cinchonains all contain a B-type linkage of the (epi)catechin subunits. Cinchonains are presumably biosynthesized by esterification of the 7'-hydroxy group of an (epi)catechin subunit with caffeic acid and a following nucleophilic attack of (epi)catechin-C8 on C3 of the caffeoyl residue. This is followed by rearomatization to form the cinchonain [26]. Compared with other berries like cranberries or lingenberries, chokeberries contain a very high amount of caffeic acid [27], which explains the occurrence of cinchonains in different polymerization degrees (dimer-pentamer). Another substance group identified, which has not been described for chokeberries so far, are the hexosides. However, it is known that these are formed in other plants such as hawthorn [28]. The detected hexoside appears with an A-type linkage between the (epi)catechin subunits. This leads to the conclusion that the type of linkage could be decisive for the formation of cinchonains or hexosides. All OPCs already characterized for the variety _Aronia melanogaster_ could also be confirmed for the variety _Aronia_\(\times\)_prunifolia_ 'Nero', with the exception of one tetramer: \(m/z\) 1151. The fragmentation experiments showed that the ether bond is located between the F-ring of the second subunit and the G-ring of the third subunit. [PERSON] et al., however, postulated that this bond is localized between the I-ring of the third and the J-ring of the fourth subunit [11]. This could indicate that different isomers of OPCs may be present in different varieties of chokeberries. It could thus be shown that the wide variety of OPCs can also be attributed to _Aronia_\(\times\)_prunifolia_ 'Nero', which leads to the presumption that these can cause a wide variety of effects. Various studies have shown that phenol-rich chokeberry extracts exhibit a number of different health-promoting benefits, such as antioxidant [4], antimicrobial [5] and antiproliferative [6] effects. It is already known that extracts enriched with oligo- or polymeric proanthocyanidins from chokeberries have provable antioxidant effects both in vitro and in vivo [29; 30], but the effects of single OPCs in dependency of their respective DP and linkage-type is insufficiently understood. The cell-free analysis of the antioxidant capacity of four selected enriched subfractions and the crude extract was performed in comparison to Trolox using the protocol for the TEAC assay. To verify the functionality of the assay, quercetin as a substance with known antioxidant effect [25] was used.