Antibacterial Activities Of Green Silver Nanoparticles-strobilanthes Crispus (AgNP-SC) Against Clinically Important Bacteria

Introduction: Silver nanoparticles has been proven to be an effective agent for antimicrobial efficacy against bacteria, viruses and other eukaryotic microorganisms. Green synthesis is one of the methods that has been developed to synthesize silver nanoparticles in environmentally-friendly conditions. It uses plant extracts as reducing and capping agents. Besides act as reducing and capping agents, bioactives such as phenolic compounds may bind to silver nanoparticles and enhance its medicinal properties. Strobilanthes crispus is a Malaysian native plant. Previous studies had shown that S. crispus contains polyphenols, catechins, alkaloids, caffeine, tannins and vitamins. Therefore, the aim of this study is to determine antibacterial activities of silver nanoparticles-Strobilanthes crispus (AgNP-SC) against clinically important pathogens such as Escherichia coli, Pseudomonas aeruginosa and Streptococcus mutans. Methods: The disc diffusion assay (DDA) was performed to investigate the inhibition zone of AgNps-Sc towards E. coli, P. aeruginosa and S. mutans. Minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) was used to determine bactericidal/bacteriostatic profile of AgNP- SC against E. coli, P. aeruginosa and S. mutans. Results: AgNP-SC (40mg/mL) shows the greatest inhibition properties (12.67±0.6mm) against S. mutans when compared to Strobilanthes crispus leaves extract (6.0±0.001mm) and blank silver nanoparticles (6.0±0.001mm). MIC values for AgNP-SC against S. mutans and E. coli were at 0.625 mg/mL and 1.25 mg/mL, respectively. Whereas the MIC value of AgNP- SC against P. aeruginosa was at 2.5 mg/mL. MBC values of AgNP-SC against E. coli, P. aeruginosa and S. mutans were at 1.25, 2.5 mg/mL respectively. Results are concentration-dependent, with higher concentration demonstrating better inhibition property. Conclusion: It can be concluded that AgNP-SC possesses bactericidal properties against S. mutans, E. coli and P. aeruginosa.