Inhibition of protease activities of periodontopathic bacteria by extracts of plants used in Kenya as chewing sticks (mswaki)

Extracts from five plants used as chewing sticks, and tannic acid, gallic acid and methyl ester of gallic acid, were tested for their ability to inhibit proteolytic activities of three strains of Bacteroides gingivalis, three strains of Bacteroides intermedius and two strains of Treponema denticola. Aqueous extract from the plants Rhus natalensis and Euclea divinorum were the most inhibitory of those tested, inhibiting by 50% the proteolytic activity of the test organisms, at concentrations of up to 200 micrograms/ml. Tannic and gallic acids had similar effects at concentrations of less than 10 micrograms/ml, while the methyl ester of gallic acid was less inhibitory. These findings suggest that extracts from plants used as chewing sticks may possess enough inhibitory components to interfere with the virulence and growth of periodontopathic bacteria in vivo, provided they are able to gain access to the subgingival sites such bacteria preferentially inhabit.