Antibacterial Activity and Attenuation of Bacteria-Induced Inflammatory Effects of Methanol Extract of Salvia miltiorrhiza against the Periodontal Pathogen Aggregatibacter actinomycetemcomitans

Aggregatibacter actinomycetemcomitans (Aa) is a gram-negative oral pathogen, whose virulence relies on Cdt toxin, bofilm formation and outer membrane protein. This study evaluated a comprehensive effects of methanol extract of Saliva miltiorrhiza (MESM) against Aa. At 1 mg/mL of MESM, ABTS, DPPH and superoxide radical scavenging activities were 84.01 ± 0.74%, 74.71 ± 2.14% and 50.97 ± 1.12%, respectively. The minimum inhibitory concentration of MESM against Aa was 250 μg/mL and the formation of biofilm was decreased by 23.35± 3.77% at 0.25 mg/mL of MESM. At 0.25 mg/mL of MESM, expression of qseC and cdtA were decreased by 3.38 and 4.32 folds, respectively. In case of Aa infected YD-38 cells, RQ values of RANKL and IL-8 were decreased from 3.40 ± 0.20 to 0.704 ± 0.018 (4.82 folds) and from 17.32 ± 1.74 to 5.50 ± 0.50 (3.15 folds) at 0.05 mg/mL of MESM. In case of Aa infected THP-1 cells, RQ value of IL-1β and TNF-α were decreased from 6,440 ± 185 to 3,512 ± 144 (1.83 folds) and from 53.65 ± 2.06 to 30.82 ± 2.04 (1.74 folds), respectively at 0.5 mg/mL of MESM. Collectively, MESM showed direct antimicrobial activity, suppression of virulence gene expression and attenuation of Aa-induced inflammatory responses.