Abstract: Streptococcus mutans and Staphylococcus aureus are major pathogenic bacteria in human oral cavity. In the present study, the antibacterial activity of procyanidins derived from grape seeds and apples against Streptococcus mutans and Staphylococcus aureus were investigated. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined by broth tube dilution and agar dilution methods, respectively. The effect of procyanidins on acid production of S. mutans was also studied by monitoring pH change of the broth during cultivation. Results showed that the MIC and MBC against S. mutans were 1.25 mg/mL and 4.00 mg/mL for apple procyanidins, and 1.75 mg/mL and 2.00 mg/mL for grape seed procyanidins, respectively. The MIC and MBC against S. aureus were 4.00 mg/mL  and 9.00 mg/mL for apple procyanidins, and 2.00 mg/mL and 6.50 mg/mL for grape seed procyanidins, respectively. Grape seed procyanidins with a concentration over 1.00 mg/mL had significant inhibitory effect on acid production of S. mutans.

Key words: procyanidins , Streptococcus mutans, Staphylococcus aureus, antibacterial