The effect of fruit extracts containing phenolic compounds on the survivability of Streptococcus mutans: an in vitro...

To examine the dose-response of various fruit extracts on the growth of S. mutans as a primary cariogenic bacterium in the oral microbiota and to determine the minimal effective concentration that inhibits its growth.

Fruit extracts of dried cranberries, cherries and raisins, as well as fresh pomegranate peel extract and pomegranate juice, were prepared and serially diluted with sterile deionized water to known concentrations of 1, 5, and 20 μg/μl. The effect of each fruit extract on the growth inhibition of S. mutans over 6 h was determined. Sterile deionized water served as a negative control and chlorhexidine (0.2%) served as a positive control.

Extracts of raisins, cranberries, and cherries, as well as pomegranate peel extract and juice, inhibited S. mutans growth in a dose-dependent manner. Significant inhibition at 6 h was observed for raisin, cranberry and cherry extracts at 5 and 20 μg/μl, as well as for pomegranate peel extract and juice at 1 - 20 μg/μl (all p < 0.05 vs. negative control). Among the highest concentrations tested, pomegranate peel extract (20 μg/μl) demonstrated the strongest inhibition, statistically significantly surpassing raisin, cranberry and cherry extracts, and pomegranate juice. Notably, the inhibitory effect of pomegranate peel extract did not differ from chlorhexidine, indicating that at this concentration it is as effective as the positive control.

Among fruit extracts, pomegranate peel extract (20 μg/μl), was the most effective inhibitor of S. mutans in vitro, matching the activity of chlorhexidine (0.2%), and could be further developed as a natural alternative for oral health applications.