Magnolia bark extract increases oral bacterial cell surface hydrophobicity and improves self-perceived breath freshness when added to chewing gum

•Chewing gum with MBE added improves the freshness of breath 60 minutes after chewing.•MBE increases bacterial surface hydrophobicity of Gram-negative bacterial strains.•MBE does not affect bacterial viability in saliva when spiking ex vivo.•MBE can be used to target Gram-negative bacteria in the oral cavity. Magnolia bark extract (MBE) is a natural product used as an anti-inflammatory, anti-platelet, and chemo-preventive agent. Here, we investigate the effects of MBE on the self-perceived freshness of breath evaluated in ten human volunteers, who chewed gum with and without MBE added, as a functional food. Furthermore, the effects of exposing oral bacteria to MBE on cell-surface hydrophobicity were determined and bactericidal effects of MBE in human saliva were assessed. Volunteers perceived freshness of breath similar directly after chewing a gum with or without MBE added, but 60 min after chewing MBE gum, freshness was perceived significantly better. Also, cell-surface hydrophobicity of Gram-negative, but not of Gram-positive bacteria, increased dose-responsively after exposure to MBE, while spiking of saliva with MBE did not affect bacterial viability. Taken together, MBE gum improves self-perceived freshness of breath likely due to an increase in cell-surface hydrophobicity of Gram-negative bacteria, instead of a bactericidal mechanism.