Molecular Insights into the Astringency of Clitoria ternatea Tea: Role of Phenolic Structure, Oral Constituents, and pH

Astringency is a key sensory attribute in plant-based products, often linked to phenolic compounds, such as anthocyanins and flavonols. This study explores the molecular basis of astringency in butterfly pea flower tea using a cell-based model comprising human saliva, oral mucosal pellicle, and HSC3 oral epithelial cells. Specifically, it aimed to (i) assess the contribution of oral constituents to phenolic compound binding (ternatins, flavonols); (ii) evaluate compound-specific interactions; and (iii) determine the influence of pH. Significant interactions with HSC3 oral cells were observed, though inhibited by salivary proteins. Structural features of phenolic compounds also modulated interactions: p-coumaroyl residues enhanced, while rhamnosyl residues reduced them. Acidic conditions promoted binding through the neutral quinoidal base of ternatins interacting with epithelial membranes, whereas at neutral pH, anionic forms were repelled by negatively charged oral cells. These findings clarify how phenolic structure, oral constituents, and pH govern oral interactions, providing molecular insight into astringency perception.