Inhibitory effects of apple polyphenols and related compounds on cariogenic factors of mutans streptococci

The inhibitory effects of apple polyphenols (APP) on the synthesis of water -insoluble glucans by glucosyltransferases (GTF) of streptococci of the mut ans group and on the sucrose-dependent adherence of the bacterial cells wer e examined in vitro. APP markedly inhibited the activity of GTF purified fr om the cariogenic bacterial cells. However, APP showed no significant effec t on the growth of the cariogenic bacteria. The strongest GTF inhibitors in APP were apple condensed tannins (ACT), a mixture of procyanidins. The 50% inhibitory doses of ACT against the GTF of S. sobrinus and that of S. muta ns were 1.5 mug/mL and 5 mug/mL, respectively. The ACT efficacy largely dep ended upon the degree of polymerization. Interestingly, while the other pol yphenols known to inhibit; GTF such as tannic acid markedly inhibited saliv ary a-amylase activity, APP and ACT only scarcely inhibited that enzyme act ivity. This means that APP and ACT might selectively inhibit the bacterial GTF activity under oral conditions.