Saliva increases the availability of lipophilic polyphenols as antioxidants and enhances their retention in the oral cavity

Objective: Lipophilic polyphenols in fruit beverages can avidly bind to surfaces of microorganisms and to blood cells and to impart upon them enhanced oxidant scavenging abilities (OSA). However, since many of the polyphenols are actually not fully soluble in water, they are therefore not available to act as effective antioxidant agents. We hypothesized that whole saliva, proteins such as albumin and mucin, human red blood cells and platelets, may all increase the "solubility" and availability of lipophilic antioxidant polyphenols thus increasing the OSA of whole saliva. Design: The OSA of whole un-stimulated human saliva, obtained from healthy donors and of combinations among saliva, mucin, blood cells, fruit beverages and reagent polyphenols were quantified by chemiluminescence, DPPH radical and tetrazolium reduction assays. Kinetics of the clearance of polyphenols from saliva after holding in the mouth for 30 s of an extract from beverages cinnamon was assayed by the Folin Ciocalteu's and the luminescence assays. Results: OSA of fruit beverages and of reagent polyphenols were markedly increased by whole saliva, mucin and by red blood cells. Polyphenols associated with a cinnamon extract were retained in the oral cavity for several hours as measured by luminescence and Folin reagent techniques. Conclusions: A new approach to explain the additional role of saliva and salivary proteins and of blood cells as enhancers of OSA of lipophilic polyphenols is presented. This might have a significant importance to assess complex interactions among polyphenols from nutrients, salivary antioxidants, salivary proteins and blood cells extravasated from injure capillaries during infection and inflammation.