Anticariogenic activities of three groups of Malaysian seaweed extracts against oral cariogenic bacteria

Abstract

Dental caries is still deliberated as one of major oral health problems worldwide. Certain types of seaweeds are reported to have antimicrobial properties. Although there were many researches about seaweed, only few of them focused on anticariogenic activities towards oral bacteria. Therefore, this study aimed to investigate the anticariogenic activities of Sargassum polycystum (S. polycystum), Caulerpa lentillifera (C. lentillifera) and Kappaphycus striatum (K. striatum) extracts against Streptococcus mutans (S. mutans) and Lactobacillus casei (L. casei).This study is divided into three phases. Phase I was to determine the best solvent in extracting the seaweeds via soxhlet apparatus and determination based on the zone of inhibition through disk diffusion method. Characterization of the seaweeds bioactive compound was done using phytochemical and Gas Chromatography Mass Spectrometry (GC-MS) analyses. Phase II was to evaluate the anticariogenic activities through determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) analyses, and to determine the synergistic effect of all three species of seaweeds extracts and antimicrobial agent (chlorhexidine) combinations using checkerboard titration method. Phase III was to investigate the mode of action of seaweed extracts on cell membrane of cariogenic bacteria. It was evaluated using method of cellular metabolites leakage at absorbance of 260 and 280 nm. All of the experimental procedures were repeated three times (n=3). Phase I revealed that all seaweed extracts that extracting using n-hexane having a higher zone of inhibition against S. mutans and L. casei when compared to 0.015% of chlorhexidine as a positive control (p<0.05). Phase II study found that the MIC and MBC values for all seaweed extracts against S. mutans and L. casei were in the range of 2.5, 10, 20 mg/mL, respectively. On the other hand, Fractional Inhibitory Concentration (FIC) indexes from the checkerboard titration method showed that the combination of all seaweed extracts and the two antibiotics were antagonistic for S. mutans and L. casei. Synergistic effect was only observed in the combination of S. polycystum and C. lentillifera extracts with streptomycin against S. mutans. Phase III demonstrated that seaweed extracts have reacted on the cell membrane of the S. mutans and L. casei. It was observed from increment of absorbance reading of cellular metabolites at OD at 260 and 280 nm. In conclusion, n-hexane is the best solvent in extracting the anticariogenic properties for the three types of seaweeds. All of the seaweed extracts impose anticariogenic activities against S. mutans and L. casei at particular concentrations and also have a synergistic effect when S. polycystum and C. lentillifera extracts were combined with streptomycin against S. mutans. The possible modes of actions of all seaweed species are leakages of cellular metabolites from cell membrane of S. mutans and L. casei. Hence, S. polycystum and C. lentillifera extracts might have a pharmaceutical potential to be an alternative substance for prevention of dental caries.