Development and Evaluation of the Antibacterial Properties of an Experimental Herbal Gel Against Cariogenic Bacteria

Recently, products with antibacterial properties derived from medicinal plants have increased as an alternative to conventional drugs. Thus, this study aimed to formulate and evaluate the antibacterial activity of an experimental gel based on Grindelia tarapacana essential oil in a bacterial consortium.

The composition of the essential oil (EO) was determined using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity of the EO against Streptococcus mutans ATCC 25175, Streptococcus sanguinis ATCC 10556, and Streptococcus salivarius ATCC 13419 was evaluated using an Agar disc diffusion and minimum inhibitory concentration methods. Five formulations of the experimental gel were prepared at 0.25%, 0.5%, 1%, 1.5%, and 2% (v/v). The antibacterial susceptibility test was evaluated using an Agar-Well diffusion assay against a bacterial consortium of S. mutans, S. sanguinis, and S. salivarius. The physical properties, pH, spreadability, gel morphology, phase separation, and drug release were evaluated. The experimental gels were compared with a chlorhexidine gel. Data were analyzed with one-way ANOVA and Kruskal-Wallis tests with a significant level of 5%.

The major components of the EO were bornyl acetate, α-isomethyl-E-nerolidol, germacrene B, E-nerolidol, α-cedrene-epoxide, fokienol, and 10-epi-γ-eudesmol. All formulations were effective in inhibiting bacterial growth. The 2% concentration presented inhibition zones (18.14 ± 1.01 mm) similar to those observed for the chlorhexidine gel (p > 0.05). All formulations were stable, without signs of separation, with adequate physical properties, and no significant differences were observed regarding the drug content with the chlorhexidine gel (p > 0.05).

The experimental gels based on G. tarapacana EO presented good physicochemical properties and were highly effective in inhibiting the growth of a cariogenic bacterial consortium.