It has been shown that, whenever oral malodor from VSC was depressed, so were the populations of oral bacteria (2–6, 21, 22). The correlation of the organoleptic score with odorigenic bacteria was investigated by several clinical studies. For example, McNamara observed that, when the bacteria-free saliva was incubated alone or added to the broth medium, no malodor was produced (6). However, when the organisms filtered from saliva were either added to the sterile saliva or added to the broth medium, malodor was produced. Results from these studies also indicated that Gram-positive oral bacteria produce little or no malodor. In contrast, Gram-negative oral bacteria produce pungent malodor. In our present study, the salivary bacteria were found around 107–108 microorganisms/mL These organisms are considered to be derived from the oral surface, especially from the tongue surface. We elected to analyze salivary bacterial counts because the test provided consistent with more reliable values with a small number of subjects. The treatment of intrinsic malodor can be achieved (1) by masking or covering malodor by flavor oils, (2) by reacting with VSC to form nonvolatile and/or odorless substances; and (3) by killing bacteria that cause the bad breath. Most breath freshening products employed flavor oils to cover or mask malodor. Some employed zinc or copper compounds to chelate VSC. Because bacteria are the major cause of breath odor, products containing effective germ-kill compounds will provide a long-lasting reduction of oral malodor. De Boever and Loesche demonstrated that a 1 week treatment of mouth rinse with 0.12% chlorhexidine gluconate in combination with a mechanical approach significantly reduced VSC levels by 73.3% (21). Rosenberg and co-workers found that a 0.2% chlorhexidine mouthwash reduced organoleptic mouth odor by 50% (22). Nevertheless, chlorhexidine, a synthetic antimicrobial agent, cannot be used in food because of the tooth staining effect and high toxicity. Our study indicated that MBE is a strong germ kill agent against oral bacteria both in Vitro and in ViVo. MBE also showed low toxicity and fewer side effects (16, 17). It may be incorporated in compressed mints and chewing gum to achieve long-lasting breath-freshening and oral-care benefits. The kill-time assay used in this study was based on the Food and Drug Administration (FDA) tentative final monograph for oral antiseptic products (23). The monograph states a requirement for a reduction of 99.9% population (3 logarithm reduction) within 10 min of exposure for specific ATCC strains. Our test showed that compressed mints containing 0.2% MBE demonstrated a significant reduction of oral bacteria (>5 log) compared to the negative controls and the flavored mints (p < 0.001). Chewing gum and compressed mint containing MBE may provide portable oral care supplementing to dentifrice, where tooth brushing is not possible. In our laboratory, we have evaluated a large number of natural and synthetic phenolic compounds against oral bacteria. Magnolol and honokiol are among a few of them. We have conducted a quantitative structure–activity relationship study (QSAR). By means of regression analysis of linear free-energy parameters and log(1/C), where C is the molar concentration of MIC, we have observed that the lipophilic character of the molecule or substituent as expressed by log P (the n-octanol/ water partition coefficient) was the most important factor in determining the activities of the compounds examined. A good correlation of log(1/C) and log P was observed within the partition coefficient range from 1.4 to 9.5. Among them, phenol showed the lowest antimicrobial effect on S. mutans, while magnolol and honokiol (log P ) 5.25) showed the highest antimicrobial effect.