Flavors and natural botanic extracts are often used in chewing gum and compressed mints for breath freshening and relief of oral malodor. The oral malodor is a result of bacterial putrification of proteinaceous materials from food or saliva. In this study, magnolia bark extract (MBE) and its two main components, magnolol and honokiol, were evaluated by the minimum inhibition concentration (MIC) test. The inhibitory effect of MBE mint was further evaluated by a kill-time assay study. In addition, an in vivo study was performed on nine healthy volunteers postlunch. Saliva samples were taken before and after subjects consumed mints and gum, with and without MBE. Listerine mouthwash was included as a positive control. The testing results indicated that MBE and its two main constituents demonstrated a strong germ-kill effect against bacteria responsible for halitosis and also Streptococcus mutans, bacteria involved in dental caries formation. The MIC of magnolol, honokiol, and MBE on Porphyromonas gingivalis, Fusobacterium nucleatum, and S. mutans ranged from 8 to 31 µg/mL. Kill-time assay results indicated that mints containing 0.2% MBE reduced more than 99.9% of three oral bacteria within 5 min of treatment. The in vivo study demonstrated that MBE containing mints reduced total salivary bacteria by 61.6% at 30 min and 33.8% at 60 min postconsumption. In comparison, the flavorless mint reduced total salivary bacteria by 3.6% at 30 min and increased total bacteria by 47.9% at 60 min. The MBE containing chewing gum reduced total salivary bacteria by 43.0% at 40 min, while placebo gum reduced total salivary bacteria by 18.0%. In conclusion, MBE demonstrated a significant antibacterial activity against organisms responsible for oral malodor and can be incorporated in compressed mints and chewing gum for improved breath-freshening benefits.
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.
Oral malodor is a major social and psychological issue that affects general populations. Volatile sulfur compounds (VSCs), particularly hydrogen sulfide (H₂S) and methyl mercaptan (CH₃SH), are responsible for most oral malodor. The objectives for this study were to determine whether allyl isothiocyanate (AITC) at an organoleptically acceptable level can eliminate VSCs containing a free thiol moiety and further to elucidate the mechanism of action and reaction kinetics. The study revealed that gas chromatograph with a sulfur detector demonstrated a good linearity, high accuracy and sensitivity on analysis of VSCs. Zinc salts eliminate the headspace level of H₂S but not CH₃SH. AITC eliminates both H₂S and CH₃SH via a nucleophilic addition reaction. In addition, a chemical structure-activity relationship study revealed that the presence of unsaturated group on the side chain of the isothiocyanate accelerates the elimination of VSCs.
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