[Effects of glycyrrhizic acid on the growth and acid-producing of Streptococcus mutans in vitro].

OBJECTIVE: To investigate the antibacterial activity of glycyrrhizic acid against Streptococcus mutans (S. mutans, ATCC 25175) in vitro. METHODS: The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of glycyrrhizic acid against S. mutans were detected using doubling dilution. The effects of glycyrrhizic acid on the growth and acidogenic profile of S. mutans and the inhibition ratio of glycyrrhizic acid on growth and acid-producing of S. mutans were investigated by detecting the Abs of bacteria suspension and the pH value of medium at definite time intervals (0 h, 3 h, 7 h, 12 h, 23 h, 40 h) during cultivation. RESULTS: The MIC determined for glycyrrhizic acid was 1.57 mg/mL and there was no bactericidal effect when concentration of glycyrrhizic acid up to 12.5 mg/mL. The glycyrrhizic acid inhibited the multiplication and acid-producing of S. mutans significantly and the effects became stronger with concentration increasing. When concentration up to 1.57 mg/mL, the inhibition ratio of glycyrrhizic acid on the growth and acid-producing of S. mutans were exceeded 80 and 70 percent, respectively. CONCLUSION: The glycyrrhizic acid can inhibit the growth and acid-producing of S. mutans in vitro.

[Effect of decoction of Radix glycyrrhizae on the growth and acid-production of Streptococcus mutans in vitro].

OBJECTIVE: To investigate the antibacterial activity of decoction of Radix glycyrrhizae against Streptococcus mutans (S. mutans) in vitro. METHODS: The decoction of Radix glycyrrhizae was prepared by boiling particles of Radix glycyrrhizae, the diameter was 0.2-3.2 mm. In distilled water and filtered, the filtrate was collected for study. The minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of the decoction against S. mutans were detected using double dilution. The effect of decoction on growth and acidogenic profile of S. mutans were investigated by detecting the Abs of bacteria suspension and the pH value of medium at definite time intervals(0, 3, 7, 12, 23, 40 h) during cultured. RESULTS: The MIC determined for decoction was 50 mg x mL(-1) and there was no bactericidal effect when concentration of decoction lower than 100 mg x mL(-1). The decoction inhibitted multiplication of bacteria significantly and the effects became stronger with concentration increasing. The decoction also inhibitted S. mutans producing acid and the effect became stronger with concentration increasing. The most efficient inhibition were observed when incubated 12 hours. CONCLUSION: The decoction of Radix glycyrrhizae can inhibite the growth and acid-production of S. mutans in vitro.

[Study on protein extraction methods for Streptococcus mutans].

OBJECTIVE: To establish an efficient and stable method for protein extraction of Streptococcus mutans. METHODS: The collected bacteria were treated by freeze-thaw and ultrasonic (method 1), ultrasonic (method 2), boiling (method 3), boiling and ultrasonic (method 4), respectively. The index such as state of bacteria broken, concentration of extracted protein and SDS-PAGE of protein were employed to evaluate the effects of above four methods. RESULTS: Beside the method 3, the other three methods could break the bacteria effectively, of which ultrasonic was the key factor. The pattern of SDS-PAGE which treated by method 1, method 2 and method 4 was almost same, but method 1 resulted in the best abundance. There was significantly difference among the four protein concentration extracted by four methods (P < 0.05). All methods exhibited good stability and reproducibility. CONCLUSION: Method of freeze-thaw and ultrasonic resulted in an efficient proteins extraction of Streptococcus mutans which demonstrated good stability and reproducibility and easy to handle.