Antimicrobial activity of Crocus sativus (Saffron) and Syzygium aromaticum (Clove) extracts against Streptococcus mutans: An in vitro study

Abstract

Objective: This study aimed to evaluate the antimicrobial activity of extracts and aqueous infusions derived from Crocus sativus and Syzygium aromaticum against Streptococcus mutans and to compare their efficacy with chlorhexidine. Methods: Experimental groups consisted of extracts and aqueous infusions prepared from Crocus sativus and Syzygium aromaticum. A commercially available 0.2% chlorhexidine mouthwash was used as the positive control. Antimicrobial activity against Streptococcus mutans ATCC 25175 strain was assessed using the disk diffusion method. Minimum Inhibitory Concentrations and Minimum Bactericidal Concentrations were determined using the broth microdilution method with well plates. The normality of the data distribution was assessed using the Shapiro–Wilk test and non-parametric statistical tests were applied. P-values below 0.05 were considered statistically significant. Results: Crocus sativus extracts and aqueous infusions did not exhibit a measurable antimicrobial effect against Streptococcus mutans. In contrast, Syzygium aromaticum extract showed concentration-dependent antibacterial activity. The antimicrobial effect of the 25% Syzygium aromaticum extract was not significantly different from that of 0.2% chlorhexidine, whereas the aqueous infusion produced a significantly smaller inhibition zone than chlorhexidine. The extract exhibited MIC and MBC values of 15.625 mg/mL and 62.5 mg/mL, respectively, indicating bactericidal activity. Conclusion: In this in vitro study, Crocus sativus showed no significant antibacterial activity against Streptococcus mutans. In contrast, both the extract and aqueous infusion of Syzygium aromaticum demonstrated bactericidal activity; the 25% extract produced inhibition zones comparable to those of chlorhexidine, whereas the aqueous infusion was effective but significantly less so than chlorhexidine. These findings highlight the potential of Syzygium aromaticum as a natural antimicrobial candidate for oral health applications. Further investigations using multispecies biofilm models and clinical studies are needed to confirm its therapeutic potential.