Affinity interactions between natural pigments and human whole saliva

Area of Science:

• Biochemistry
• Materials Science

Background:

• Pigments are widely used in food and pharmaceuticals.
• Understanding pigment interactions with biological fluids like whole saliva (WS) is crucial for product stability and efficacy.
• The binding characteristics of common dietary pigments with WS are not fully elucidated.

Purpose of the Study:

• To test the hypothesis that pigment affinity for WS is not influenced by pigment functional groups, temperature, pH, or salt concentration.
• To quantify the binding affinity of specific pigments to WS.
• To investigate the impact of environmental factors on pigment-WS interactions.

Main Methods:

• Determined affinity constants using surface plasmon resonance (SPR) and fluorescence quenching.
• Assessed pigment-protein complex formation and precipitation.
• Measured mass-uptake of pigments under varying temperatures, pH, and salt concentrations.

Main Results:

• The binding affinity order for WS was theaflavin (TF) > curcumin (Cur) > cyanidin (Cy).
• Pigments formed rapid, strong, and nearly irreversible complexes with WS proteins, leading to precipitation.
• Pigment mass-uptake was significantly affected by functional groups, molecular weight, temperature, pH, and salt concentration.

Conclusions:

• Pigment-protein complexes readily deposit onto WS surfaces and are difficult to remove.
• Physicochemical conditions (temperature, pH, salt concentration) can be regulated to modulate pigment complexation with WS.