Abstract

Ellagic acid, a natural herb extract from Galla Chinensis in traditional Chinese medicine, shows antimicrobial activity to certain bacteria. The present study evaluated the effect of Ellagic acid on the growth of oral bacteria as well as their generation of water-insoluble glucan and adhesion to saliva-coated hydroxyapatite (S-HA) beads. Streptococcus mutans ATCC 25175, Streptococcus sanguis ATCC 10556, Streptococcus salivarius ATCC 25975, Actinomyces naeslundii ATCC 12104, Actinomyces viscosus ATCC 15987, Lactobacillus rhamnosus ATCC 53103, Porphyromonas gingivalis ATCC 33277 and Bacteroides forsythus ATCC 43037 were the bacterial cell lines used in this study. Antibacterial activity of Ellagic acid was determined by using adenosine triphosphate (ATP) bioluminescence assay at various concentrations from 0.125 to 8 mg/ml. Anthrone method was used to evaluate the level of water-insoluble glucan generated by oral bacteria. The numbers of 3H-thymidine labeled bacteria attached to S-HA was counted by scintillation counting method. Sprague Dawley rats were orally fed with 0.5mg/mLellagic acid for 28 days and their behaviours and excretions were monitored. Ellagic acid reduced bacterial metabolic rates and inhibited the growth of the tested bacterial strains. The water-insoluble glucan generated by S. mutans and its adhesion to S-HA were reduced. Ellagic acid demonstrated no toxicity in animals fed for 28 days. Ellagic acid might be a promising compound for the development of antimicrobial agents against oral pathogens in human, thereby reducing the incidence of dental caries.

Key words: Ellagic acid, Galla chinensis, adenosine triphosphate bioluminescence assay, oral bacteria.

Abbreviation

S-HA, Saliva-coated hydroxyapatite; MIC, minimal inhibitory concentrations; ATP, adenosine triphosphate; TPY, tryptone-peptone-yeast; SD,Sprague-Dawley; CMP, scintillation counting.