Abstract
This study evaluates the antibacterial activity of the Copaifera duckei Dwyer oleoresin and two isolated compounds [eperu-8(20)-15,18-dioic acid and polyalthic acid] against bacteria involved in primary endodontic infections and dental caries and assesses the cytotoxic effect of these substances against a normal cell line. MIC and MBC assays pointed out the most promising metabolites for further studies on bactericidal kinetics, antibiofilm activity, and synergistic antibacterial action. The oleoresin and polyalthic acid but not eperu-8(20)-15,18-dioic provided encouraging MIC and MBC results at concentrations lower than 100 μg mL−1. The oleoresin and polyalthic acid activities depended on the evaluated strain. A bactericidal effect on Lactobacillus casei (ATCC 11578 and clinical isolate) emerged before 8 h of incubation. For all the tested bacteria, the oleoresin and polyalthic acid inhibited biofilm formation by at least 50%. The oleoresin and polyalthic acid gave the best activity against Actinomyces naeslundii (ATCC 19039) and L. casei (ATCC 11578), respectively. The synergistic assays combining the oleoresin or polyalthic acid with chlorhexidine did not afford interesting results. We examined the cytotoxicity of C. duckei oleoresin, eperu-8(20)-15,18-dioic acid, and polyalthic acid against Chinese hamster lung fibroblasts. The oleoresin and polyalthic acid were cytotoxic at concentrations above 78.1 μg mL−1, whereas eperu-8(20)-15,18-dioic displayed cytotoxicity at concentrations above 312.5 μg mL−1. In conclusion, the oleoresin and polyalthic acid are potential sources of antibacterial agents against bacteria involved in primary endodontic infections and dental caries in both the sessile and the planktonic modes at concentrations that do not cause cytotoxicity.
Highlights
The oral bacterial microbiome encompasses ∼700 commonly occurring phylotypes, about half of which can be present at any time in any individual
This study examines the antibacterial activity of the C. duckei Dwyer oleoresin and its secondary metabolites against bacteria involved in primary endodontic infections and dental caries in both the planktonic mode and the sessile mode
The Minimum Inhibitory Concentration (MIC; the lowest concentration of the test compound that is capable of inhibiting microorganism growth) and the Minimum Bactericidal Concentration (MBC; defined as the lowest concentration of the test compound at which no bacterial growth occurs) of the oleoresin and the pure metabolites were determined in triplicate; the microdilution broth method in 96-well microplates was employed
Summary
The oral bacterial microbiome encompasses ∼700 commonly occurring phylotypes, about half of which can be present at any time in any individual. Dental caries is one of the most common biofilm-dependent oral diseases among humans (Bowen, 2002). Endodontic infections have a polymicrobial nature, with obligate anaerobic bacteria conspicuously dominating the microbiota in primary infections (Narayanan and Vaishnavi, 2010). Microorganisms and their products play an essential part in the development of pulp and periapical diseases and account for endodontic treatment failure (Guerreiro-Tanomaru et al, 2015). Chemomechanical preparation of the infected root canal with antimicrobial agents, followed by obturation and coronal restoration, provides a favorable outcome (Narayanan and Vaishnavi, 2010). The search for alternative antibacterial agents without or with few side effects is urgent (Peng et al, 2013)
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