## 3 Results
### Identification and Characterization of OPCs in Purified Subfractions via Fragment Spectra
Based upon these fragments, it is proposed that the m/z 739 ion is a cinchonin dimer, which is structured of two (epi)catechin subunits with a B-type linkage and a conjugated phenylpropanoid moiety at the A-ring of the upper (epi)catechin unit. The \(m/z\) 1315 ion is proposed as a cinchonin tetramer (Figure 3 (5)). Therefore, the fragmentation pattern of \(m/z\) 1315 is delved into in more detail to confirm the proposed structure (Figure 5). Based on the predicted molecular formula C\({}_{69}\)H\({}_{55}\)O\({}_{27}\) ([M-H]\({}^{-}\)), it is expected that the cinchonin included only B-type linked (epi)catechin subunits along with a phenylpropanoid moiety. The main fragment ion with \(m/z\) 737 is formed by a QM fission between the F-ring and the G-ring with the loss of two (epi)catechin subunits. Another possible fragment of  
Figure 5: Presumed fragmentation pathway of the cinchonin tetramer found in _Aronia_\(\times\)_prunifolia_ ’Nero’ with HRMS in negative ionization mode. The fragmentation mechanisms involved mainly retro-Diels–Alder reaction (RDA) and quinone methide cleavage (QM). this QM fission is \(m/z\) 575. Via a subsequent RDA which leads to the loss of the K-ring and parts of the L-ring, the \(m/z\) 423 fragment ([M-152-H]\({}^{-}\)) is formed. The \(m/z\) 405 ion is generated by an additional loss of water compared to the m/z 423 fragment. A loss of water at the parent ion resulted in \(m/z\) 1297 ([M-18-H]\({}^{-}\)). The structure of this fragment is not displayed in Figure 5 because the position where the water cleavage takes place is not clear. A QM fission which results in the loss of one (epi)catechin subunit leads to the fragment with \(m/z\) 1025 ([M-290-H). The presence of the \(m/z\) of 449 ([M-288-H]\({}^{-}\)), which results from a further QM cleavage, which is located between the C-ring and the D-ring and leads to the loss of three (epi)catechin subunits, indicates that the molecule is a tetramer consisting of B-type linkages of (epi)catechin units with the conjugated phenylpropanol moiety at the A-ring. The separation via QM cleavage of three (epi)catechin subunits at the C-ring could also lead to the ion with \(m/z\) 865. The \(m/z\) 695 fragment ([M-170-H]\({}^{-}\)) is generated by an additional RDA reaction in combination with a loss of water of the \(m/z\) 865 fragment. The \(m/z\) 1163 ion ([M-152-H]\({}^{-}\)) is presumably formed by RDA reaction, e.g., of the B-ring and parts of the C-ring. A loss of H\({}_{2}\)O of this fragment ion resulted in \(m/z\) 1145. The specific fragments and the exact mass suggest that the molecule is a procyanidin, which is made up of four (epi)catechin subunits with B-type linkages and with a conjugated phenylpropanol moiety at the A-ring of the tetramer. The isomers with \(m/z\) 1603 (Figure 3 (6)) with a proposed molecular formula of C\({}_{84}\)H\({}_{67}\)O\({}_{33}\) ([M-H]\({}^{-}\)) were detected as quasi-molecular ions with \(m/z\) 801 ([M-2H]\({}^{2-}\)), which could be confirmed by the mass difference of 0.5 Da between the isotopic pattern signals (Supporting Information Figure S16). The mass difference of 288 Da compared to \(m/z\) 1315 suggests that the molecule is a cironan pentamer, with the 288 Da corresponding to another (epi)catechin unit. A QM cleavage at the L-ring resulted in the loss of a (epi)catechin subunit and \(m/z\) 1313 ([M-290-H]\({}^{-}\)). If the QM fission occurs at the I-ring of the molecule, either the fragments with \(m/z\) 1027 and \(m/z\) 575 or \(m/z\) 1025 and \(m/z\) 577 are generated. The C\({}_{9}\) moiety is positioned on the fragments \(m/z\) 1027 or \(m/z\) 1025 at the A-ring of the molecule. Another possible position for a QM cleavage is the F-ring, which then resulted in \(m/z\) 865 and \(m/z\) 737. In this case, \(m/z\) 865 represents three (epi)catechin subunits and \(m/z\) 737 two (epi)catechin subunits with the conjugated phenylpropanol moiety. An additional QM fission at the C-ring of the fragment ion \(m/z\) 737 resulted in \(m/z\) 449 ([M-288-H]\({}^{-}\)).