Inhibitiory effects of herbs on hydroxyapatite-adsorbed glucosyltransferase and Streptococcus mutans

Objective: To investigate the effects of 14 herbal extracts on the activity of glucosyltransferase and the growth of Streptococcus mutans ATCC 25175 which were adsorbed onto saliva-coated hydroxyapatite. Methods: Fourteen herbs ie. Abutilon indicumus (Chinese bell flower), Acacia catechu (catechu tree), Andrographis paniculata, Areca catechu (betel nuts), Camellia sinensis (Chinese black tea), Cassia alata (candle bush), Curcuma domestica (turmeric), Eugenia caryophillus (clove), Harrisonia perforata, Hibiscus sabdariffa (roselle), Psidium guajava (guava), Rhinacanthus nasotus, Spilanthes aemella and Streblus asper were extracted with 50% or 95% ethanol and dried. Glucosyltransferase was partially purified from bacterial media by ammonium sulfate precipitation. The dialyzed enzyme was adsorbed onto hydroxyapatite coated with whole saliva. In separate experiment, Streptococcus mutans grown in tryptic soy broth was adsorbed onto saliva-coated hydroxyapatite. The herbal extracts at 0.5% concentration (w/v) were then tested to the hydroxyapatite-adsorbed enzyme or bacteria using ethanol as a control. The enzyme activity was assayed using [¹⁴C-glucose] sucrose as a substrate while the bacteria growth was determined by colony counting on mitis salivarious agar. The data were analyzed by ANOVA. Results: It was found that all herbal extracts strongly inhibited the activity of hydroxyapatite-adsorbed glucosyltransferase with percentage inhibition ranged from 59.96 ± 2.08% to 97.76 ± 0.17% (p < 0.01). Guava extract was the most potent inhibitor while candle bush was the least. For bacterial growth, all herbal extracts, except Harrisonia perforata, also showed significant inhibitory effect with percentage inhibition ranged from 17.44 ± 2.47 to 99.98 ± 0.00%. The most potent inhibitor was turmeric. Conclusion: All these data indicate that ethanol extracts of the studied herbs may be used as an anti-plaque and anti-bacteria agents. Chulalongkorn Dental Research Fund 3/2005