Eco-friendly synthesis of silver nanoparticles: Enhancing optimization reaction, characterization, and antimicrobial properties with Lantana camara from geothermal area

• Lantana camara from geothermal area is an effective bioreductor for synthesizing silver nanoparticles (AgNPs), producing particles smaller than those in previous research, with the smallest size being 44 nm. • The AgNPs synthesized from leaves of Lantana camara (AgNPs-LLc) showed the smallest particle size among AgNPs created from other plants in the same geothermal location, achieved through optimization using the Response Surface Methodology. • The green synthesis of AgNPs-LLc demonstrated significant antimicrobial properties, especially as an antibacterial agent against Gram-positive bacteria like S. aureus and E. coli , with effectiveness increasing at higher concentrations. • Despite showing promise as an antimicrobial agent, AgNPs-LLc did not exhibit substantial antifungal activity against C. albicans , indicating a need for more research to fully understand and optimize their antifungal capabilities. Green synthesis methods for producing silver nanoparticles (AgNPs) have garnered significant attention for their potential in medical applications. Despite the known potential of Lantana camara in AgNP synthesis, there is a lack of studies investigating its application when grown in extreme geothermal environments, which may influence the properties and efficacy of the synthesized nanoparticles. This research aimed to fabricate AgNPs utilizing aqueous extract from Lantana camara , a plant growing in an extreme geothermal manifestation area. Another aim of this study is to evaluate their antimicrobial activity. Qualitative and quantitative phytochemical analyses of the plant's leaves were also conducted. Reaction optimization was performed using response surface methodology (RSM), employing a central composite design (CCD) approach. The characterization of AgNPs involved UV-Vis spectroscopy, FTIR, SEM-EDX, and PSA. The antimicrobial testing was conducted against Gram-positive bacterium ( S. aureus ), Gram-negative bacterium ( E. coli ), and the fungus ( C. albicans ). The phytochemicals analysis revealed that the L. camara leaf extract contains flavonoids, phenolics, saponins, tannins, and steroids, lacking alkaloids and terpenoids, with total phenolic and flavonoid contents of 11.94 mg (GAE/g) and 6.70 mg (QE/g), respectively. The AgNPs exhibited a spherical shape with a surface plasmon resonance (SPR) peak at a wavelength of 417 nm, and the smallest particle size measured was 44 nm. Based on FTIR analysis, AgNPs have functional groups such as OH, NH, C=C, and C H that were identified as groups involved in the reduction of Ag + to Ag 0 during the green synthesis of AgNPs. The AgNPs demonstrated the lowest antifungal activity against C. albicans . In summary, the aqueous leaf extract of L. camara from geothermal manifestation areas can serve as a bioreductant for AgNPs, exhibiting higher antibacterial activity against Gram-positive bacteria compared to Gram-negative ones.