Antibacterial Effects of Juglone and Its Derivatives against Oral Pathogens

Antibacterial activities of the red wood materials were examined against seven oral pathogens and compared to that of seven 1,4-naphthoquinone's derivatives. Active constituent of red wood was purified and identified as juglone (5-hydroxy-1,4-naphthoquinone) by various spectra. Juglone showed strong the growth inhibition against Porphyromonas spp. and Streptococcus mutans at 2.0 mg/disc and revealed the strong growth inhibition against Actinobacillus viscosus, S. sobrinus and S. salivarius at 1.0 mg/disc. In comparisons with 1,4-naphthoquinone's derivatives, 2-hydroxy-1,4-naphthoquinone had the strong growth inhibition against Porphyromonas spp., Streptococcus spp. and A. viscosus at 1.0 mg/disc. Furthermore, 5,8-dihydroxy-1,4-naphthoquinone had the strong growth inhibition against A. viscosus, S. salivarius, and S. sobrinus at 1 mg/disc. Our results indicated that 1,4-naphthoquinone's derivatives containing hydroxyl-, methyl-, and methoxy- seem to be required here for antibacterial activities, suggesting that some derivatives may be useful as a preventative agent against dental diseases.