[1][2] Color stabilization of oenin at a higher pH can be explained by self-aggregation of the flavylium cation and copigmentation with the Z-chalcone form.

[3] In the presence of procyanidin C2, the red color of oenin appears more stable.

However, the HPLC chromatogram shows a decrease in the amplitude of the peaks of oenin and procyanidin C2.

Concomitantly, a new peak appears with a maximal absorption in the red region.

[4] Oenin alone is not oxidized in the presence of grape polyphenol oxidase, whereas it is degraded in the presence of a crude grape PPO extract and of caftaric acid forming anthocyanidin-caftaric acid adducts.