Antibacterial Activity of Acmella Paniculata Extracts Against Oral Bacteria (Streptococcus Mutans)

Acmella paniculata, popularly known as the toothache plant, has been widely used as a
traditional medicine to help treat diseases associated with toothache and gum infections.
Streptococcus mutans is a common bacterium that can cause dental caries. This study
aims to determine the antibacterial activity of A. paniculata extracts against S. mutans.
Eight samples of A. paniculata leaves and flowers had been successfully extracted using
n-hexane, dichloromethane, acetone and methanol. All samples were tested for
antibacterial activity using the disc diffusion assay, the minimum inhibitory
concentration (MIC), and the minimum bactericidal concentration (MBC). From the
screening, only n-hexane leaves extract (APLHE), methanol leaves extract (APLME),
n-hexane flower extract (APFHE) and dichloromethane flower extract (APFDE)
exhibited antibacterial activity against S. mutans. Therefore, all four samples were
tested with an antibiofilm and time-kill assay to determine the reduction activity and
time-kill rate against S. mutans. The results showed that flower extracts exhibit more
antibacterial activity against S. mutans when compared with leaves extracts. Thus,
scanning electron microscopy (SEM) and transmission electron microscopy (TEM)
were used to examine the morphology of S. mutans under treatment with APFHE and
APFDE. According to both micrograph observations, the shape of S. mutans changed
from coccus and rounded to elongated and lysed after treatments. Then, by using GCMS,
the major phytochemical compound found in both APFHE and APFDE is fatty
acids (such as hexadecanoic acid, oleic acid, and linoleic acid). Finally, transcriptomic
analysis was performed on S. mutans that had been treated with APFDE. The results
proved that APFDE affected the biosynthesis of peptidoglycan, gene expression,
quorum sensing, citrate cycle and glycolysis pathway of S. mutans. In conclusion, the
antibacterial activity of APFDE disrupted various biological processes and pathways of
S. mutans.