The green tea polyphenol (−)‐epigallocatechin gallate precipitates salivary proteins including alpha‐amylase: biochemical implications for oral health

Hara K, Ohara M, Hayashi I, Hino T, Nishimura R, Iwasaki Y, Ogawa T, Ohyama Y, Sugiyama M, Amano H. The green tea polyphenol (−)‐epigallocatechin gallate precipitates salivary proteins including alpha‐amylase: biochemical implications for oral health. Eur J Oral Sci 2012; 120: 132–139. © 2012 Eur J Oral Sci Green tea is a popular drink throughout the world, and it contains various components, including the green tea polyphenol (−)‐epigallocatechin gallate (EGCG). Tea interacts with saliva upon entering the mouth, so the interaction between saliva and EGCG interested us, especially with respect to EGCG–protein binding. SDS‐PAGE revealed that several salivary proteins were precipitated after adding EGCG to saliva. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) peptide mass fingerprinting indicated that the major proteins precipitated by EGCG were alpha‐amylase, S100, and cystatins. Surface plasmon resonance revealed that EGCG bound to alpha‐amylase at dissociation constant ( K d ) = 2.74 × 10 −6 M, suggesting that EGCG interacts with salivary proteins with a relatively strong affinity. In addition, EGCG inhibited the activity of alpha‐amylase by non‐competitive inhibition, indicating that EGCG is effective at inhibiting the formation of fermentable carbohydrates involved in caries formation. Interestingly, alpha‐amylase reduced the antimicrobial activity of EGCG against the periodontal bacterium Aggregatibacter actinomycetemcomitans . Therefore, we considered that EGCG–salivary protein interactions might have both protective and detrimental effects with respect to oral health.