Plant-based synthesis of silver nanoparticles using aqueous leaf extracts of Cinchona calisaya Wedd. and Cinchona pubescens Vahl: physicochemical characterisation and biological activities

Green synthesis approaches to produce silver nanoparticles (AgNPs) have gained considerable attention recently due to their eco-friendliness and diverse applications in biotechnology, healthcare and environmental management. The present study explores the biogenic synthesis of AgNPs using aqueous extracts of Cinchona calisaya Wedd. and Cinchona pubescens Vahl. The research focuses on the physicochemical characterisation of AgNPs using several analytical techniques such as UV-visible spectroscopy, transmission electron microscopy (TEM), dynamic light scattering, Fourier transform infrared spectroscopy, powder X-ray diffraction (PXRD), and energy dispersive X-ray spectroscopy. The obtained nanoparticles exhibited diverse sizes ranging from 23 ± 3 to 50 ± 9 nm, with a spherical shape observed on TEM images and with elemental composition containing Ag, N, C, O, etc. FTIR data indicated that chemicals containing carboxylic, hydroxyl, alkanes and carbonyl groups are bonded on the surface of AgNPs, while PXRD data indicated that the AgNPs were crystalline. Furthermore, a deep evaluation of the biological activities of the AgNPs was conducted. AgNPs exhibited moderate antioxidant, antibacterial and antifungal activities. Additionally, the produced AgNPs exhibited a dose-dependent potency for environmentally friendly vector control (larvicidal action) at the concentrations ranging from 200 to 400 ppm. The total phenolic content of C. calisaya and C. pubescens extracts and AgNPs was between 288.73 ± 20.42 mg/100 mL and 464.47 ± 16.44 mg/100 mL. This comprehensive investigation provides valuable insights into the potential of C. ledgeriana and C. pubescens leaf extracts as reducing and capping agents for AgNPs synthesis. The outcomes of this study have far-reaching implications for green nanotechnology, eco-friendly materials science and biomedicine. The diverse properties of AgNPs facilitate innovative healthcare and environmental sustainability applications, highlighting their potential to tackle significant global issues.