Naturally Occurring Phenolic Antibacterial Compounds Show Effectiveness against Oral Bacteria by a Quantitative Structure−Activity Relationship Study

Abstract

Natural and synthetic phenolic compounds were evaluated against oral bacteria. A quantitative structure-active relationship approach was applied to the germ-kill activity for a range of phenolic compounds. The lipophilicity and steric effects were found to be two key factors in determining germ-kill activity. The optimum lipophilicity, measured by the logarithm of the octanol/water partition coefficient, or log P, was found to be 5.5 for Fusobacterium nucleatum , a Gram-negative type of oral bacteria that causes bad breath. The optimum log P was found to be 7.9 for Streptococcus mutans , a Gram-positive type of oral bacteria that causes tooth decay. The steric effect of substituents ortho to the phenolic group was found to be critical in reducing antibacterial activity despite having increased lipid solubility approaching the optimum lipophilicity value. The antibacterial activity of phenolic compounds is likely exerted by multiple functions, primarily comes from its ability to act as a nonionic surface-active agent therefore disrupting the lipid-protein interface.

Harvestman Phenols and Benzoquinones: Characterisation and Biosynthetic Pathway

“…A set alkyl phenols were tested against oral bacteria revealing that the ortho-substituents on the phenolic groups decreased the biological activity [31]. In fact, o-phenol 18 displayed higher MIC values ( Table 4).…”

“…The dramatic MIC difference displayed by 18 against Gram-positive and Gram-negative bacteria is caused by the lipophilicity of this compound. Therefore, Gram-negative bacteria such as P. aeruginosa, have up to 25% of lipidic content and can retain the liposoluble phenols, while Gram-positive species, such as B. pumilus have 0% to 3%, therefore allowing the phenol to cause cellular membrane damage [31].…”

Effect of a Sugar-Free Chewing Gum Containing Magnolia Bark Extract on Different Variables Related to Caries and Gingivitis: A Randomized Controlled Intervention Trial

“…MBE has been shown to be an effective bactericidal agent against oral bacteria both in vitro and in vivo [Namba et al, 1982;Chang et al, 1998;Ho et al, 2001;Greenberg et al, 2007;Greenberg et al, 2008]. The in vitro antimicrobial activity of MBE through the minimum inhibitory concentration and the kill-time assay tests were evaluated.…”

“…Studies in vitro have shown that some of these extracts possess antibacterial activity against cariogenic and periodontopathic bacteria [Ho et al, 2001;Greenberg et al, 2007;Greenberg et al, 2008]; however, the clinical effects still remain unproven [Wallace, 2004]. Magnolia bark extract (MBE) is a plant extract obtained from the bark of magnolia that has been widely used in traditional Chinese medicine for 2,000 years [Watanabe et al, 1983].…”

Antibiofilm activity of natural substances derived from plants

“…Its frequent and prolonged use presents many collateral effects, such as changes in the taste of food and a burning feeling on the tip of the tongue (Greenberg et al, 2008;More et al, 2008;Porto et al, 2009).…”