pigmentcopigmentation

Pigment copigmentation is a color-modifying phenomenon in which a pigment molecule forms non-covalent associations with one or more copigment molecules, resulting in altered absorption properties and color. It is most extensively studied for plant pigments such as anthocyanins, but it also occurs in dyes, foods, and beverages.

The interaction is typically driven by π–π stacking, hydrogen bonding, and van der Waals forces between the pigment and copigment. When complexed, the system often exhibits a bathochromic shift (red shift) and hyperchromic effect, which means the color shifts toward longer wavelengths and the color intensity increases. The exact outcome depends on the structures of both partners, solvent, pH, and temperature.

Common copigments include flavones and flavonols (for example quercetin, kaempferol), hydroxycinnamic acids, and other phenolics. Copigmentation is a major factor in natural petal colors, stabilizing vivid hues; in wine, it contributes to the depth and stability of red color as anthocyanins interact with phenolic copigments.

It can help stabilize colors against pH changes, light exposure, and metal ions, and can influence perceived color intensity in various products. Conditions such as higher copigment concentration, lower polarity solvents, and temperature can alter the extent of copigmentation.

Understanding pigment copigmentation aids in horticulture and food industries by enabling color prediction and enhancement, as well as in studying pigment-based signaling in plants. It is distinct from covalent pigment modification and from metal complexation, though all can contribute to observed colors in complex systems.