Green tea catechins have been widely used as an anticariogenic or antiplaque additive to mouthrinses, toothpastes, etc. Since their retention in the oral cavity is the determinant for thecaries preventive effects, the oral pharmacokinetic study was performed by assessing salivary concentrations of catechins with time after oral application using high-performance liquid chromatography with diode array detection. The optimized method enabled to simultaneously quantify eight catechins in the concentration range of 0.05-25.0μg/ml in saliva and mouthrinses with high resolution, recovery, and precision. Mouthrinsing experiments with the aqueous solutions of green tea extract (5.0mg/ml) revealed that each catechin maintained the salivary concentration at μg/ml levels for 1-60 min after mouthrinsing, especially (-) -epigal-locatechin gallate and (-) -gallocatechin gallate showed concentrations over 10μg/ml even after 60 min. When using the commercially available mouthrinses containing green tea extract, catechins were found in saliva up to 60 min after mouthrinsing, although their salivary concentrations were much lower. The retentive degree of catechins depended on their concentrations in mouthrinses and the number of times of mouthrinsing. Mouthrinsing with the green tea extract solution under optimal conditions would retain catechins in the oral cavity at least for 60 min after oral application, maintaining their salivary concentrations to show the potential caries preventive effects.
