Isolation and identification of 5-carboxy-pyranoanthocyanins in beverages from cherry (Prunus cerasus L.)

Novel pyranoanthocyanins were identified by HPLC–ESI-MSn in fermented and unfermented fruit juices from cherry (Prunus cerasus L.). The two major compounds, namely 5-carboxy-pyranocyanidin 3-O-(2G-glucosylrutinoside) and 5-carboxy-pyranocyanidin 3-O-rutinoside were isolated by a combination of high-speed countercurrent chromatography with semi-preparative HPLC. Their structures were fully elucidated by means of NMR spectroscopy and mass spectrometry. As minor compounds 5-carboxy-pyranocyanidin 3-glucoside, 5-carboxy-pyranopeonidin-3-glucoside, and 5-carboxy-pyranopeonidin 3-rutinoside could be identified.These compounds are formed during storage of the juice through the reaction of pyruvic acid with the respective genuine anthocyanins.Industrial relevanceFor the consumers the color of fruit juices is one of the most important quality markers. However due to a fast degradation of anthocyanins, changes in color from purple/red hues to orange/brown hues can be observed during storage. The main objective of this study was the isolation, structural characterization and evaluation of pigments that are formed during aging of fruit juices. Pyranoanthocyanins were reported to possess a color stabilizing effect. In the present study it could be demonstrated that the color contribution of these newly formed pigments to the overall color of fruit juice was overestimated. Instead, the formation of polymeric pigments yields the highest impact (> 80%) on the color of aged fruit juices.