Ryota Nomura1, Jumpei Ohata2, Masatoshi Otsugu2, Rena Okawa2, Shuhei Naka3, Michiyo Matsumoto-Nakano3, Kazuhiko Nakano2. 1. Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan. Electronic address: rnomura@dent.osaka-u.ac.jp. 2. Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan. 3. Department of Pediatric Dentistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Abstract
OBJECTVES: Citrus unshiu has been shown to exhibit antimicrobial effects against citrus diseases. In the present study, C. unshiu was divided into flavedo, albedo, fruits, and leaves; the inhibitory effects of these extracts on Streptococcus mutans, a major pathogen of dental caries, were investigated. DESIGN: C. unshiu specimens were separated into flavedo, albedo, fruits, and leaves. First, pH values and polyphenol amounts in Citrus extracts were measured. In addition, Citrus extract was added to the bacterial suspensions of S. mutans MT8148, and inhibitory effects of C. unshiu extracts on MT8148 for antimicrobial activity, bacterial growth, and biofilm formation were analyzed. These assays were also performed using C. sinensis extracts. RESULTS: Among these extracts, albedo exhibited a pH value closest to neutral, while the fruits exhibited the most acidic pH value; the pH values significantly differed between these extracts (P < 0.05). In addition, the amounts of polyphenols were significantly higher in albedo than in other extracts (P < 0.001). All extracts showed inhibitory effects on MT8148 for antimicrobial activity, bacterial growth and biofilm formation. These inhibitory effects were significantly stronger in flavedo, albedo, and fruits, compared with leaves (P < 0.05). Furthermore, extracts of Citrus sinensis also showed inhibitory effects on S. mutans, although these effects were weaker than the effects of C. unshiu. CONCLUSION: These results suggest that extracts from C. unshiu fruits exhibit inhibitory effects on S. mutans, among which albedo may be especially useful for dental caries prevention due to its neutral pH and abundant polyphenols, in addition to its inhibitory effects.
OBJECTVES: Citrus unshiu has been shown to exhibit antimicrobial effects against citrus diseases. In the present study, C. unshiu was divided into flavedo, albedo, fruits, and leaves; the inhibitory effects of these extracts on Streptococcus mutans, a major pathogen of dental caries, were investigated. DESIGN: C. unshiu specimens were separated into flavedo, albedo, fruits, and leaves. First, pH values and polyphenol amounts in Citrus extracts were measured. In addition, Citrus extract was added to the bacterial suspensions of S. mutans MT8148, and inhibitory effects of C. unshiu extracts on MT8148 for antimicrobial activity, bacterial growth, and biofilm formation were analyzed. These assays were also performed using C. sinensis extracts. RESULTS: Among these extracts, albedo exhibited a pH value closest to neutral, while the fruits exhibited the most acidic pH value; the pH values significantly differed between these extracts (P < 0.05). In addition, the amounts of polyphenols were significantly higher in albedo than in other extracts (P < 0.001). All extracts showed inhibitory effects on MT8148 for antimicrobial activity, bacterial growth and biofilm formation. These inhibitory effects were significantly stronger in flavedo, albedo, and fruits, compared with leaves (P < 0.05). Furthermore, extracts of Citrus sinensis also showed inhibitory effects on S. mutans, although these effects were weaker than the effects of C. unshiu. CONCLUSION: These results suggest that extracts from C. unshiu fruits exhibit inhibitory effects on S. mutans, among which albedo may be especially useful for dental caries prevention due to its neutral pH and abundant polyphenols, in addition to its inhibitory effects.