Investigation of antimicrobial effect of Salvia officinalis and Juglans regia extracts on cariogenic microbial strains from oral cavity: An in-vitro study

Abstract

Introduction: Due to the high prevalence of tooth decay with microbial cause and huge treatment costs, especially in high-risk groups such as people with dry mouth; prevention and control of decay is essential. On the other hand, considering the favor of the world community to complementary medicine treatments and the need to extract medicine from natural substances and medicinal plants; the use of plant extracts has been considered in biomedical sciences due to their antimicrobial, antioxidant, properties. This laboratory study was conducted to investigate the antimicrobial effect of salvia officinalis extract and walnut tree trunk (Juglans regia) separately and in combination on caries-causing microbial species of the oral environment. Methods: This study was an invitro research in which the hydroalcoholic (ethanolic) extract of herbal plants Juglans regia and Salvia officinalis was prepared by maceration method. Then, to determine the antimicrobial effectiveness, tests to determine the inhibitory activity of the extracts (MIC-MBC-disk agar diffusion) were performed for each of the extracts separately and the combination of the two extracts.Data were analyzed using one-way ANOVA test. p<0.05). MTT (Methy Thiazol Tetrazolium) colorimetric test method was used to investigate the effect of cytotoxicity of the extracts in their effective dose. Results: Examining the antimicrobial effect of ethanolic extract of sage, walnut trunk and their combination showed that the extracts had antimicrobial effects. In comparing the antimicrobial effect of the extracts between the study groups and the control group (chlorhexidine), for Streptococcus mutans, Lactobacillus casei, and Candida albicans, the MIC values for sage extract were 475 μg/mL, 237 μg/mL, and 31.25 mg/mL, respectively. and for walnut trunk extract 29.6 μg/mL, 475 μg/mL and 15.62 mg/mL and for their combination 118 μg/mL, 475 μg/mL and 15.52 mg/mL and the MBC values reported for sage are 0.95 mg/mL respectively, 475 μg/mL and 62.5 mg/mL, respectively 29.6 μg/mL, 0.95 mg/mL and 31.25 mg/mL for walnut trunk and 237 μg/mL, 0.95 mg/mL and 31.25 mg/mL for their combination. . MTT assay results showed that the extracts had no cytotoxicity effects at the minimum inhibitory concentration, however, pure chlorhexidine was toxic at a commercial concentration of 0.22%. Conclusion: According to the results of our research, the ethanolic extract of Salvia officinalis, Juglans regia trunk, and their combination have antibacterial effects against microorganisms that are effective in tooth decay and oral disease. The largest diameter of inhibitory zone was recorded in Salvia officinalis extract for Streptococcus mutans bacteria,. Juglans regia extract had a lower MIC than Salvia officinalis and the combination of two extracts. Also, Candida albicans showed less sensitivity to the extracts. However, no synergistic effect was observed in the combination of two extracts. Cytotoxicity studies (MTT assay) showed that in effective concentrations, these extracts have no toxic effect on L929 cell-line.