Synthesis of Silver Nanoparticle Using Bioactive Phenolic Compound Extracts of Leucas aspera and Leucas cephalotes and Evaluation of its Antibacterial Activity

The present study was carried out to investigate the antibacterial activity of the bioactive phenolic extract from Leucas aspera and Leucas cephalotes. The phenolic compounds were extracted using water: ethanol (1:3, v/v) by hydroethanolic extraction method. The hydroethanolic extracts were subjected to qualitative and FTIR analysis as a confirmatory step for the presence of phenolics. Synthesis of silver nanoparticle from both plants was carried out by acid hydrolysis method and subjected to UV-visible spectrophotometry, SEM, TEM and XRD analysis, for confirmation of tagged bioactive compound to AgNO3. The nanoparticle size distribution ranged between 50-94 nm in L. aspera and 40-67 nm in L. cephalotes. The antibacterial study was carried out using both crude phenolic extract and synthesized nanoparticles and tested against 5 pathogens namely Escherichia coli (ATCC® 8739™), Pseudomonas aeruginosa (ATCC® 25619™), Staphylococcus aureus (ATCC® 6538™), Bacillus subtilis (ATCC® 11774™) and Klebsiella pneumonia (ATCC® 13882™) for their antibacterial activity. From present study, the crude extract of L. cephalotes showed good antibacterial effect against test pathogen species wherein highest inhibition was observed in, P. aeruginosa, followed by B. subtilis and S. aureus with an average zone of inhibition of 23, 14 and 12 mm, E. coli and K. pneumonia measured 9 and 7 mm. The crude extract of L. aspera showed the highest inhibition in P. aeruginosa followed by S. aureus and E. coli with an average zone of inhibition of 12,11 and 10 mm B. subtilis and K. pneumonia measured 8 and 7 mm. Statistical analysis was calculated using One way ANOVA and was found to be statistically significant with p < 0.05.