Inhibitory effect of grape seed extract (GSE) on cariogenic bacteria

Streptococcus mutans plays an important role in the development of dental caries in humans. Although fluoride and other preventive efforts have led to a dramatic decline in dental caries, the ability to control the actual infection has been limited. Therefore, this study was aimed at investigating in details the effect of a grape seed extract (GSE) on the growth and the biofilm formation of S. mutans. Cytotoxicity assay of GSE was used to determine the non-toxic concentrations to the host cell (HEp-2 cell line). Antimicrobial activity of GSE was examined in vitro on S. mutans isolate to determine the minimum inhibitory concentration (MIC) by using microtiter plate method. The potentiality of GSE on the bacterial adherence (biofilm) was also tested on growing cells on the bottom of cell culture plate. The presence of S. mutans increases the free radical stress, which initiates the DNA fragmentation of the host cells. In addition, the free scavenging activity of GSE was measured by using 1,1-dipicryl-2-phenyl hydrazyl (DPPH) assay; DNA fragmentation was carried out in the presence and absence of GSE treatment. The results obtained indicate that the non-toxic dose of GSE and its major constituents (gallic acid, catechin and epicatechin) was 15, 7, 5 and 15%, respectively. All the treatments have the ability to inhibit the growth of S. mutans and biofilm formation with priority to GSE and epicatechin (80.98 and 66.25%, respectively). Moreover, the GSE could scavenge the free radicals up to 85% and completely inhibit the DNA fragmentation. GSE, especially epicatechin therefore showed an interesting action on S. mutans and could be used for lowering this potentially cariogenic species in the oral cavity.   Key words: Streptococcus mutans, grape seed extract (GSE), cytotoxicity, biofilm, non-toxic dose.