The interactions of epigallocatechin-3-gallate with human whole saliva and parotid saliva.
OBJECTIVE
The aim of the present study was to assess the null hypothesis that the astringency and loss of lubrication in the oral cavity are not related to the properties of the epigallocatechin-3-gallate (EGCG) adlayer, the affinity and the entropy-drive of EGCG binding to saliva.


METHODS
The mass, thickness, and viscoelasticity of the EGCG adlayer and the temperature dependence of EGCG adsorption onto saliva surfaces were determined by quartz crystal microbalance with dissipation (QCM-D). The affinities of EGCG to human whole saliva (WS) and to parotid saliva (PS) were carried out by QCM-D monitoring and fluorescence quenching.


RESULTS
The stiffer and more compact EGCG adlayers were formed on saliva surfaces at various concentrations of EGCG. The affinity for EGCG binding to WS was higher than that to PS. The precipitation of EGCG/saliva was temperature-dependent. The driving force of EGCG binding to saliva is dominated by the hydrogen bond, the hydrophobic reaction, and the entropy-drive, which were confirmed by the FTIR spectra and the measurement of temperature- dependence, respectively.


CONCLUSIONS
The viscoelasticity of the EGCG adlayer, the affinity of EGCG to saliva, and the priority of EGCG binding to hydrophobic proteins on the mucosa may account for the oral astringency and loss of lubrication.
Yao
Jiang-Wu
JW
Department of Restorative Dentistry and Biomaterials, Xiamen Stomatological Research Institute, Fujian Medical University, China. dentyjw@126.com <dentyjw@126.com>
Lin
Chang-Jian
CJ
Chen
Guo-Yang
GY
Lin
Feng
F
Tao
Tao
T
D000327:Adsorption; D000328:Adult; D001252:Astringents / Q000737:chemistry / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D011232:Chemical Precipitation; D004548:Elasticity; D019277:Entropy; D005260:Female; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D055767:Immobilized Proteins; D008153:Lubrication; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000378:metabolism; D011480:Protease Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D012463:Saliva / Q000187:drug effects*; D012469:Salivary Glands / Q000378:metabolism; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000187:drug effects*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors*; D014783:Viscosity; D055815:Young Adult
D001252:Astringents; D055767:Immobilized Proteins; D011480:Protease Inhibitors; D012471:Salivary Proteins and Peptides; D002392:Catechin; C045651:epigallocatechin gallate; D014568:Urokinase-Type Plasminogen Activator