OBJECTIVETo investigate the antibacterial activity of decoction of Radix glycyrrhizae against Streptococcus mutans (S. mutans) in vitro.

METHODSThe 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.

RESULTSThe 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.

CONCLUSIONThe decoction of Radix glycyrrhizae can inhibite the growth and acid-production of S. mutans in vitro.