Evaluation of natural products for anti-halitosis activity based on methyl mercaptan inhibition

Halitosis, or oral malodour, is primarily caused by volatile sulphur compounds (VSCs) such as methyl mercaptan, which are produced by anaerobic bacteria includingPorphyromonas gingivalis(P. gingivalis) andFusobacterium nucleatum (F. nucleatum). While conventional antibacterial mouthwashes are widely used, their adverse effects-such as microbial imbalance and dental staining-necessitate safer, natural alternatives. This study aimed to identify plant-derived agents with anti-halitosis, antibacterial, and anti-inflammatory activity, with low cytotoxicity. A total of 252 medicinal plant extracts were screened for biological activity. Antibacterial effects againstP. gingivalisandF. nucleatumwere evaluated using spectrophotometry and agar well diffusion assays. Anti-inflammatory activity was assessed by nitric oxide inhibition in LPS-stimulated macrophages. Cytotoxicity was measured in gingival epithelial cells and oral keratinocytes. The anti-halitosis effect was determined based on inhibition of methyl mercaptan production using Oral Chroma, a gas chromatography-based device. Of the 252 extracts, 32 demonstrated significant antibacterial activity, VSC suppression, and low cytotoxicity. Among these,Polygoni Cuspidati Radix, Rhei Rhizoma, Pini Ramulus, andPiperis Longi Fructusexhibited the most potent inhibition of methyl mercaptan production. Combination treatments using these extracts maintained efficacy at lower concentrations. The findings suggest that these herbal extracts may serve as effective, safe, and accessible anti-halitosis agents. Their dual antibacterial and anti-inflammatory effects support their potential use in oral hygiene formulations, offering a natural alternative for the prevention and management of halitosis.