Antibacterial activity and stability of Sophora flavescens and Schisandra chinensis extracts against Streptococcus mutans KCCM 40105

This study aimed to select natural materials with antibacterial activity against Streptococcus mutans (S. mutans) KCCM 40105 and determine their most efficient extraction conditions. The antibacterial activity was stable under various treatment conditions. Of the 17 material groups, extracts of Sophora flavescens (SF) and Schisandra chinensis (SC) showed antibacterial activity against the S. mutans strain. Measuring the antibacterial activity based on ethanol concentration revealed that the 30% ethanol extracts of SF and SC showed the highest antibacterial activity as observed by the inhibition zones of 10.69 and 14.49 mm, respectively. The minimum inhibitory concentrations of the 30% ethanol extracts of SF and SC against the S. mutans strain were 2.0 and 5.0 mg/mL, respectively. Heat stability was confirmed; however, the 30% ethanol extract of SC was inactive at pH values ≥6.0. The antibacterial activity of the 30% ethanol extract of SF and SC treated with nine enzymes was the same at 10 ppm and 100 ppm. However, the activity tended to decrease marginally in the 1,000 ppm concentration treatment group.