Abstract
The purpose of this study was to determine the antimicrobial activity of plant extracts such as a crude catechin extract from green tea, black tea extract, a crude catechin extract from black tea, (-) -epigallocatechingallate (EGCg), extract from branch-bark of Morus, and Eucalyptus extract on oral microorganisms. The antimicrobial activity was measured by minimum inhibitory concentrations. Extracts from branch-bark of Morus and Eucalyptus showed strong antibacterial activity against gram-positive bacteria such as Streptococcus species, Actinomyces spesies, and L. casei, however, these compounds did not exhibit antibacterial activity less than 1600ppm against gram-negative bacteria except for P. gingivalis. Another plant extract showed a weak effect on gram-positive bacteria. All of the tested plant extracts had no antimicrobial activity less than 1600ppm against P. melaninogenica, F. nucleatum, and V. parvula.
