Antibacterial efficacy of curcumin, allicin, gingerol and cinnamon against Enterococcus faecalis: An in vitro study

Bioactive compounds from plants have potential antimicrobial activity. The aim of this in vitro study was to evaluate the antimicrobial efficacy of curcumin, allicin, gingerol and cinnamon compared to 4% sodium hypochlorite (NaOCl) against Enterococcus faecalis and its biofilm.

The dry herbal compounds were diluted with dimethyl sulfoxide (DMSO). Antimicrobial activity was evaluated using agar diffusion test, minimum inhibitory concentration (MIC) assay, minimum bactericidal concentration (MBC) test, time kill study, and biofilm susceptibility assay. The zone of inhibition (ZOI) was determined using agar diffusion test on Muller Hinton (MH) agar plates. MIC was evaluated using the tube dilution method. Root canals of extracted human anterior teeth were instrumented, split into two halves, autoclaved, and incubated with brain heart infusion broth containing E. faecalis for 21 days to form a biofilm. The susceptibility of the biofilm to the test solutions was evaluated by counting bacterial colonies on MH agar.

NaOCl exhibited potent antimicrobial activity under all tested parameters. Allicin showed a significantly greater ZOI, while curcumin showed the least MIC among the tested herbal extracts (P < 0.05). MBC varied widely among the groups with no significant difference between allicin and cinnamon (P > 0.05). Gingerol and cinnamon were significantly superior to the other groups killing E. faecalis within 4-4.2 min (P < 0.05). Curcumin, gingerol, and cinnamon were equally efficacious as NaOCl in completely eradicating E. faecalis biofilm (P > 0.05).

NaOCl emerged as the most efficacious antibacterial agent and all herbal extracts showed significant antibacterial activity against E. faecalis.