Investigation of antibacterial constituents from Zanthoxylum Linn

Zanthoxylum plants are popularly used for treatment of dental disease in the traditional Chinese medicine. This investigation was aimed at study of antibacterial activities of six Zanthoxylum plant extracts and isolated compounds against several oral pathogens, i.e. Streptococcus mutans (ATCC 25175), Actinomyces naeslundii (ATCC 12104), Actinobacillus actinomycetemicomtans (ATCC 43717). Objectives: To evaluate the antibacterial activity of eleven ethanolic extracts obtained from six different Zanthoxylum species against oral pathogens. Methods: Six Zanthoxylum species are Z. esquirolii Levl, Z. dimorphyllum Hemsl, Z. nitidum, Z. armatum DC, Z. scandens, Z. lactum Drake. The antibacterial effect of their extracts was evaluated via conventional microbiological methods, agar diffusion method and minimum inhibitory concentration (MIC) assay. Further analysis via bioassay-guided fractionation and purification of the plant Z. dimorphyllum resulted in the isolation of four known compounds identified as Scoparone; 6,7,8-Trimethoxycoumarin; Canthin-6-one; Syringaresinol. Results: In the agar diffusion assay, Z. lactum showed the strongest anti-bacteria activity against the two tested oral pathogens, and the rest of the extracts revealed moderate activity against A. naeslundii and A. actinomycetemicomtans. In the MIC assay, Z. lactum appeared to be the most active extract against all 3 oral bacteria. Z. dimorphyllum and Z. nitidum exhibited activity against A. naeslundii. Canthin-6-one showed MIC values of 62.5, 31.2 and 15.6 ƒÝg/mL for S. mutans, A. naeslundii, and A. actinomycetemicomtans, respectively. Conclusions: The results suggested that Cathin-6-one is one of the key factors contributed to the antibacterial activity of Z. dimorphyllum. Canthin-6-one is a well known antimicrobial compound with a broad antimicrobial spectrum. However, the activity of Canthin-6-one has not been studied on oral bacteria. Furthermore, it is necessary to understand its toxicity in addition to its antimicrobial property. Study is in progress to explore its other potential activity for treatment of oral disease.