Proanthocyanidins (PAs) are the secondary metabolites that are responsible
for many positive effects related to ruminant nutrition and health. We were
looking for naturally modified PAs that cannot be found in plants. To develop
the production methods of such rare PAs we used a unique method where
these are modified by oxidation in alkaline conditions. It included the collection of 300 plant samples from the Botanical Garden of the University of
Turku, Finland. From the preliminary screening, 130 plant samples have procyanidin and prodelphinidin rich oligomers and polymers, which has polyphenol oxidase enzyme activity. The PAs in these plant samples were
extracted and analyzed as such by UPLC connected to Waters XEVO TQ triple quadrupole mass spectrometer. Then the plant extracts were oxidized by an
oxidation test using a pH 10 buffer. These samples were further studied by
QExactive Orbitrap mass spectrometers, in order to characterize the modified
PA structures. In addition, the proanthocyanidin oligomers and polymers in
oxidized and non-oxidized samples were quantified by Multiple Reaction
Monitoring (MRM) methods by UPLC-MS/MS. These results suggested that
prodelphinidin (PD) rich oligomers have higher chances to modify the PA structure in the alkaline condition whereas procyanidin (PC) rich oligomers
and polymers have less chances to modify the structure. However, the PC
helps to stable the tannin structure. On the other hand, if the PD is absent in
the sample then the structure is more stable, or no oxidation occurs.