Synthesis of Silver Nanoparticles Using Aqueous Extract of Medicinal Plants’ (<i>Impatiens balsamina</i>and<i>Lantana camara</i>) Fresh Leaves and Analysis of Antimicrobial Activity

Plant-mediated synthesis of nanomaterials has been increasingly gaining popularity due to its eco-friendly nature and cost-effectiveness. In the present study, we synthesized silver (Ag) nanoparticles using aqueous extracts of fresh leaves of <i>Impatiens balsamina</i> and <i>Lantana camara</i> medicinal plants as bioreducing agents. This method allowed the synthesis of nanoparticles, which was confirmed by ultraviolet-visible (UV-Vis) spectrophotometry and transmission electron microscopy (TEM). UV-Vis spectra and visual observation showed that the color of the fresh leaf extracts of <i>L. camara</i> and <i>I. balsamina</i> turned into grayish brown and brownish yellow, respectively, after treatment with Ag precursors. In addition, TEM analysis confirmed that AgNO₃ solutions for all concentrations produced Ag nanoparticles and their average size was less than 24 nm. Moreover, aqueous leaf extracts of <i>I. balsamina</i> and <i>L. camara</i> were separately tested for their antimicrobial activity against Gram-positive <i>Staphylococcus aureus</i> and Gram-negative <i>Escherichia coli</i> bacteria. The results showed that the bacterial growth was inhibited by the extracts containing Ag nanoparticles. Statistical calculation performed using the Tukey test showed that zones of inhibition for the two bacteria produced by the aqueous leaf extracts of <i>L. camara</i> containing 3 mM and 5 mM Ag precursors were not significantly different from that by ciprofloxacin as positive control. On the contrary, there was significant difference between the zone of inhibition for <i>E. coli</i> by ciprofloxacin and that by the extracts of <i>I. balsamina</i> leaves containing 3 mM and 5 mM Ag precursors. A similar result was observed on the zone of inhibition for <i>S. aureus</i> by the extracts of <i>I. balsamina</i> leaves containing 3 mM Ag precursor. It was shown that the aqueous extracts of fresh <i>L. camara</i> leaves containing Ag nanoparticles were comparable to ciprofloxacin in inhibiting bacterial growth.