BACKGROUND AND OBJECTIVE: Medical treatment of tooth decay is associated with the possibility of allergic reactions and increased bacterial resistance to antibiotics. This study aimed to evaluate the phenolic compounds and antimicrobial effects of the hydroalcoholic extracts of Aloe vera and Glycyrrhiza glabra against four cariogenic bacteria in vitro.

METHODS: In this empirical study, hydroalcoholic extracts of Aloe vera and Glycyrrhiza glabra were obtained using the percolation method. Then preparing standard strains of Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguinis, Actinomyces viscosus. Antibacterial activity of extracts were determined by micro broth dilution method. Concentration of phenolic compounds, flavonols and flavonoid were determined using the optical density (OD) method.

FINDINGS: In this study, total phenolic content and concentrations of flavonols and flavonoids were 3, 37 and 10 mg/g in the Aloe vera extract, respectively, while they were 36, 78 and 14 mg/g, respectively in the extract of Glycyrrhiza glabra. Regarding the frequency of cariogenic bacteria, MIC and MBC of the Glycyrrhiza glabra extract for Streptococcus mutans were 0.5 and 1 mg/ml, respectively, while they were 0.25 and 0.5 mg/ml for Streptococcus salivarius, 0.125 and 0.5 mg/ml for Streptococcus sanguinis, and 0.25 and 0.5 mg/ml for Actinomyces viscosus, respectively. Moreover, MIC and MBC of the Aloe vera extract were 4 and 16 mg/ml for Streptococcus mutans, 0.5 and 2 mg/ml for Streptococcus salivarius, 1 and 4 mg/ml for Streptococcus sanguinis, and 1 and 2 mg/ml for Actinomyces viscosus, respectively. MIC and MBC of Aloe Vera extract (4 and 16 mg/ml) was significantly higher than the Glycyrrhiza glabra extract (0.5 and 1 mg / ml) (p<0.05).

CONCLUSION: According to the results of this study, the hydroalcoholic extract of Glycyrrhiza glabra exerted greater antibacterial effects against the studied bacteria compared to the Aloe vera extract due to the higher concentration of phenolic compounds. In addition, Streptococcus mutans showed higher resistance against the herbal extracts compared to the other bacteria