Cytotoxicity of Oral Hygiene Products Containing Zanthoxylum limonella Pericarp Extract

The essential oil from standardized Zanthoxylum limonella pericarps extract possesses antiseptic, local anesthetic and anti-inflammatory activities. Thus, the natural oral hygiene products have been developed to use for the prevention of dental caries and periodontal disease. Objectives: To evaluate the cytotoxicity of three oral hygiene products containing Zanthoxylum limonella pericarp extract on L929 cell culture using MTT assay. Methods: The three oral hygiene products- mouthwash, oral aerosol and toothpaste- were diluted into the concentrations of 1:25, 1:50, 1:75, 1:100, and 1:200. Monolayer (1 x 10⁵ cells/ml) of L929 cells was used as test cells in a 96-well tissue-culture plate. After incubation at 37⁰ C in 5% CO₂ for 24 hr in the presence of each diluted product, cell survival was determined using MTT assay. Results: In accordance with a requirement of ISO (the International Organization for Standardization), at the same levels of concentrations of 1:25 and 1:50, all experimental products proved toxic (p>0.05). At the dilution of 1:75, toothpaste was non-cytotoxic, while oral aerosol seemed to be less toxic than mouthwash (mean percentages of cell viability were 116.69, 87.14, and 66.97, respectively) (p<0.05). All products were non-cytotoxic at the dilution of 1:200. Conclusions: It was concluded that the toothpaste and oral aerosol containing Zanthoxylum limonella pericarp extract were non-cytotoxic or mild-cytotoxic. They could be further used for clinical trial as salivary flow and water (during toothbrushing) can dilute concentration of the products to the non-toxic dilution. This study was supported by a grant for collaborative research between public and private sectors, the Office of Higher Education Commission, Thailand.