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 H 2 O 2 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 ζ-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 μg/mL). Within the same range, treatment with Kf 1 -, Kf 2 -, and Kf 3 -AgNPs decreased the generation of DPPH (IC 50 57.02-2.09 μg/mL) and H 2 O 2 (IC 50 3.15-3.45 μg/mL) radicals. This study highlights the importance of using inorganic nanomaterials to improve the biological performance of plant extracts as an efficient nanotechnological approach.