## 3 Results
### Identification and Characterization of OPCs in Purified Subfractions via Fragment Spectra
Another detected substance with an \(m/z\) of 1025 might suggest a cinchanain with an A-Type linkage, however, due to the difference between the exact mass of an A-Type cinchanain with C\({}_{54}\)H\({}_{41}\)O\({}_{21}\)\({}^{-}\) (calculated \(m/z\) 1025.2146) and the accurate mass of the observed ion \(m/z\) 1025.2311 (equates to 16.5 ppm deviation), this idea must be forfeit. The other possibility is that the substance is a hexoside trimer (Figure 3 (3)) with an A-type linkage with a molecular formula of C\({}_{54}\)H\({}_{45}\)O\({}_{23}\) ([M-H]\({}^{-}\)) and an exact mass of \(m/z\) 1025.2357. Therefore, the mass errors of the accurate masses of the three detected hexoside isomers are -4.6 ppm for \(m/z\) 1025.2311, -2.1 ppm for \(m/z\) 1025.2336 and -1.4 ppm for \(m/z\) 1025.2343. Due to the proposed molecular formula and the accurate mass of the three isotopes, it is assumed that they are three hexoside trimer isotopes with an A-type linkage. This assumption is supported by the MS\({}^{2}\) experiments, which are described in detail hereinafter. The suggested fragments and the possible fragmentation pathway as well as the postulated structure of the hexoside trimer in negative ionization mode are presented in Figure 4.  
Based on the fragmentation, it is expected that the hexose residue is attached to the C-ring of the upper (epi)catechin subunit of the A-type OPC trimer. The main fragment ion \(m/z\) 735 ([M-290-H]\({}^{-}\)) resulted in a QM cleavage of one (epi)catechin subunit. This subunit loss indicates that the C-ring and the D-ring are connected through an A-type linkage. A further hint for this position of the linkage is the fragment ion with \(m/z\) 573,  
Figure 4: Presumed fragmentation pathway of the hexoside trimer found in _Arontia_\(\times\)_prunifolia_ ‘Nero’ with HRMS in negative ionization mode. The fragmentation mechanisms mainly involved retro-Diels–Alder reaction (RDA), quinone methide cleavage (QM) and heterocyclic ring fission (HRF). which is formed via HRF. It is assumed that the fragment \(m/z\) 447 is generated from further QM fission at the fragment \(m/z\) 735. Via the RDA reaction of the H-ring and parts of the I-ring, the fragment \(m/z\) 873 ([M-152-H]\({}^{-}\)) is generated. The additional loss of H\({}_{2}\)O at this fragment leads to \(m/z\) 855. A further RDA reaction of the fragment ion \(m/z\) 873 resulted in the fragment with \(m/z\) 721 ([M-152-H]\({}^{-}\)), and by a combined RDA with a loss of H\({}_{2}\)O, \(m/z\) 703 ([M-152-18-H]\({}^{-}\)) is formed. Based on the characteristic fragments, it is assumed that the \(m/z\) 1025 ion is a hexoside procyanidin, which consists of three (epi)catechin subunits with an A-type linkage between the first and second subunit. In addition to the above-mentioned cinchonin with \(m/z\) 1027, three additional cinchonians were detected. The \(m/z\) 739 ion with the suggested molecular formula of C\({}_{39}\)H\({}_{31}\)O\({}_{15}\) ([M-H]\({}^{-}\)) is assigned to a cinchonin dimer formed out of (epi)catechin units (Figure 3 (4)). Due to the fragmentation, it is expected that the phenylproponoid moiety is conjugated on the A-ring of the molecule. The loss of H\({}_{2}\)O of the parent molecule formed the ion with \(m/z\) 721. By QM fission at the C-ring, either \(m/z\) 451 ([M-288-H]\({}^{-}\)) or \(m/z\) 449 and \(m/z\) 289 are generated. Cleavage of the entire B-ring of the fragment ion \(m/z\) 449 or of the pyrocatechol of the phenylproponoid moiety leads to \(m/z\) 339 ([M-110-H]\({}^{-}\)). The main fragment ion \(m/z\) 587 ([M-152-H]\({}^{-}\)) is formed by the RDA reaction of the E-ring and parts of the F-ring or the B-ring and parts of the C-ring of the molecule. In addition to a H\({}_{2}\)O loss, the ion with \(m/z\) 569 ([M-152-18-H]\({}^{-}\)) is generated. An additional RDA at the fragment ion \(m/z\) 587 resulted in \(m/z\) 435. The cleavage of the entire E-ring results in \(m/z\) 629 ([M-110-H]\({}^{-}\)).