Enhancement of color stability of cyanidin-3-O-glucoside by copigmentation with punicalagin: multispectral analysis and computer simulation

This study investigated the copigmentation mechanism between punicalagin (PUN) and cyanidin-3-O-glucoside (C3G) using spectroscopic analysis, thermodynamic evaluation, and quantum chemical modeling. UV-VIS spectra revealed enhanced absorbance and red shifts upon increasing PUN concentration to the C3G solution, indicating intensified color. Copigmentation was most effective at acidic pH (3–6) and declined at higher temperatures. Thermodynamic parameters indicated a spontaneous, exothermic interaction between PUN and C3G, involving hydrogen bonding and π–π stacking. FT-IR, 1 H NMR, and IGMH analyses confirmed these interactions and revealed that α -PUN formed more stable complexes with C3G than β -PUN, due to cooperative aromatic-polar interactions and more favorable stacking geometry. Quantum calculations supported the greater stability of α -C3G/PUN complexes. Furthermore, PUN significantly improved the thermal, light, and storage stability of C3G. These findings provide molecular-level insights into anthocyanin-ellagitannin copigmentation and demonstrate the potential of PUN as a natural copigment for improving color stability in food systems.