Insights into anthocyanin stability and infusion color in purple leaf teas driven by co-pigment flavonoid interactions.

Purple leaf tea (PLT) is gaining attention for its vibrant color and potential health benefits. This study focuses on the critical role of co-pigmentation in dictating the vibrant color and stability of its anthocyanins. PLT infusions exhibit a distinct reddish-purple hue, contained approximately 10.3-fold higher total anthocyanin levels (average 34.33 μg/mL) than green leaf tea as determined by chromatography, with delphinidin-3-O-galactoside (D3G; average 15.02 μg/mL) and cyanidin-3-O-galactoside (average 7.97 μg/mL) being dominant. Co-pigments markedly intensified D3G's coloration. For instance, gallic acid and quinic acid induced hypsochromic shifts, decreasing λmax by 7-9 nm. Thermally (80 °C, 15 h), gallic acid significantly improved D3G stability (21.0 % retention), correlating with strong docking affinity (-3.605 kcal/mol) via H-bonds and π-π stacking. Conversely, epigallocatechin gallate dramatically reduced D3G stability (1.7 % retention). These specific molecular interactions critically influence PLT's anthocyanin color expression and thermal stability, offering key insights for quality optimization.