Antibacterial activity of Acmella paniculata extracts against Streptococcus mutans

Acmella paniculata, also known as 'Subang nenek' in Malaysia, has been used to treat diseases such as toothache and gum infections. People called it a toothache plant, and it has been widely used as traditional medicine. Therefore, this study aims to investigate the antibacterial activities of A. paniculata leaves and flowers extracts towards Streptococcus mutans by using disc diffusion assay, minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) methods. Besides, the anti-biofilm activity of all the extracts also been determined by using a crystal violet assay. As the results, n-hexane and methanol extracts from leaves showed the highest inhibition zone towards S. mutans  when compared to DCM and acetone extracts. Meanwhile, for the flowers extract, n-hexane and DCM showed the highest inhibition zone towards S. mutans compared to methanol and acetone extracts. The best results were then tested for MIC and MBC tests. As for the MIC values of n-hexane and methanol leaves extracts were 25 mg/mL, respectively, and the MBC values were 50 and 100 mg/mL, respectively. Whereas MIC values for n-hexane and DCM flowers extracts were 12.5 mg/mL, respectively, and the MBC values were 50 mg/mL, respectively. Biofilm formation of S. mutans  showed decrement up to 70% after exposure to both leaves extract (n-hexane and methanol) and n-hexane flower extract. Still, it differed when exposing to DCM flower extract, and the result showed that the biofilm activities of S. mutans were inhibited at 80% after treated with DCM flowers extracts. In conclusion, n-hexane leaves extract, methanol leaves extract, n-hexane flowers extract, and DCM flowers extract of A. paniculata demonstrated bactericidal properties against S. mutans.