Melastoma malabathricum stem bark acetone extract as an anti-bacterial agent against Streptococcus mutans

Melastoma malabathricum, also known as 'senduduk' in Malaysia, has been used as traditional medicine for diseases such as toothache, dysentery, haemorrhoids and stomachache. Therefore, the objective of this study is to investigate the biological activity of Melastoma malabathricum stem bark extracts (MMSBE) towards Streptococcus mutans. This investigation involved a few methods, which at first is the determination of minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC). Next is by analyzing the time-kill curve, anti-biofilm activity, scanning electron and transmission electron microscopic analyses. Later, next-generation sequencing (NGS) was done to determine differential regulation genes of treated and non-treated S. mutans. Lastly, confirmation of differential regulation genes was done by RT-PCR analysis. As for the results, M. malabathricum stem bark acetone extract (MMSBAE) showed the greatest inhibition concentrations towards S. mutans, followed by M. malabathricum methanol extract (MMSBME). Values of MIC and MBC (MMSBAE) were 1.25 mg/mL and 5 mg/mL. Meanwhile, MIC and MBC values of MMSBME were 5 mg/mL and 40 mg/mL. MMSBAE was chosen to further analyze its anti-bacterial activity against S. mutans. Time kill curve analysis found that MMSBAE possessed bacteriostatic properties against S. mutans. Besides, SEM and TEM analyses revealed that there were some changes to S. mutans cell morphology after treated with MMSBAE while Next gene sequencing analysis revealed significant (p<0.05) gene expression with multiple targets by MMSBAE, which caused inhibition of S. mutans biofilm formation activity. As for the conclusion, this study highlights the potential of MMSBAE as a new promising anti-S. mutans agents.