Cranberry harbors several flavonoids that display biological properties against Streptococcus mutans. Objective: The aim of this study was to evaluate the influence of individual cranberry flavonoids on several virulence attributes of S. mutans. Methods: The ability of quercetin, myricetin and their glycosides to inhibit the glucan production by purified glucosyltransferases (GTFs), the membrane-associated F-ATPase and glycolytic activity was determined. Furthermore, we examined whether the flavonoids interfere with gtfBCD gene expression by S. mutans. The vehicle solution (10% ethanol, v/v) was used as controls. Results: Quercetin and myricetin inhibited partially the activity of GTF B and C both in solution (50 to 60% inhibition, at 250 µg/ml) and on surface of saliva-coated hydroxyapatite (20 to 40% inhibition). The flavonoids also inhibited significantly the activity of F-ATPase and the glycolytic pH drop by suspensions of S. mutans cells (P<0.05). Furthermore, the expression of gtfB was decreased by more than 40% at either mid- or late-exponential growth phase of S. mutans growing in the presence of the flavonoids compared to the same microorganism growing in the absence of the agents; there was no significant difference in levels of 16SrRNA between treated and non-treated cells (P>0.05). Conclusions: Our data show that quercetin and myricetin are active compounds in cranberry that modulate the virulence factors involved in S. mutans acidogenicity and biofilm formation. (NIDCR # 1R01DE016139-01).

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