Green Synthesis of Silver Nanoparticles with Extracts from Kalanchoe fedtschenkoi: Characterization and Bioactivities

In this work, the hexane, chloroform, and methanol extracts from Kalanchoe fedtschenkoi were utilized to green-synthesize silver nanoparticles (Kf(1)-, Kf(2)-, and Kf(3)-AgNPs). The Kf(1)-, Kf(2)-, and Kf(3)-AgNPs were characterized by spectroscopy and microscopy techniques. The antibacterial activity of AgNPs was studied against bacteria strains, utilizing the microdilution assay. The DPPH and H2O2 assays were considered to assess the antioxidant activity of AgNPs. The results revealed that Kf(1)-, Kf(2)-, and Kf(3)-AgNPs exhibit an average diameter of 39.9, 111, and 42 nm, respectively. The calculated zeta-potential of Kf(1)-, Kf(2)-, and Kf(3)-AgNPs were -20.5, -10.6, and -7.9 mV, respectively. The UV-vis analysis of the three samples demonstrated characteristic absorption bands within the range of 350-450 nm, which confirmed the formation of AgNPs. The FTIR analysis of AgNPs exhibited a series of bands from 3500 to 750 cm(-1), related to the presence of extracts on their surfaces. SEM observations unveiled that Kf(1)- and Kf(2)-AgNPs adopted structural arrangements related to nano-popcorns and nanoflowers, whereas Kf(3)-AgNPs were spherical in shape. It was determined that treatment with Kf(1)-, Kf(2)-, and Kf(3)-AgNPs was demonstrated to inhibit the growth of E. coli, S. aureus, and P. aeruginosa in a dose-dependent manner (50-300 mu g/mL). Within the same range, treatment with Kf(1)-, Kf(2)-, and Kf(3)-AgNPs decreased the generation of DPPH (IC50 57.02-2.09 mu g/mL) and H2O2 (IC50 3.15-3.45 mu g/mL) radicals. This study highlights the importance of using inorganic nanomaterials to improve the biological performance of plant extracts as an efficient nanotechnological approach.