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In order to investigate the physicochemical properties and bioactivities of AgNPs prepared using green and chemical approaches and further explore the related antibacterial mechanism, one kind of chemical AgNPs (C-AgNPs) and three kinds of green AgNPs (G-AgNPs) mediated with aqueous extracts of Morus alba L. were prepared and characterized. All G-AgNPs displayed higher antioxidant activities in DPPH radical scavenging, reducing power and total antioxidant assays than C-AgNPs and extracts. Meanwhile, all G-AgNPs exerted significantly (P < 0.05) enhanced antimicrobial activities against various pathogens compared with C-AgNPs and extracts. Among prepared AgNPs, ML-AgNPs mediated with aqueous extract of Morus alba L. leaves exhibited the most powerful antibacterial effect with the largest inhibition zones (13.11 ± 0.76 mm for S. aureus, 13.27 ± 0.22 mm for E. coli) and the lowest minimum inhibition concentrations against S. aureus (6.125 μg/ml) and E. coli (3.125 μg/ml). ML-AgNPs could inhibit the growths of S. aureus and E. coli in time- and dose-dependent modes, and even could disrupt the bacterial structure integrality resulting in the leakage of intracellular contents. G-AgNPs, especially ML-AgNPs, with remarkable bioactivities could replace C-AgNPs as related agents applied in agriculture and medicine. [ABSTRACT FROM AUTHOR]

Plant mediated biosynthesis of nanoparticles is going important due to simple processes and non-toxic materials utilization. Rhizophora stylosa (RS) mangrove leaf extract was successfully used as a bioreductor in the production of AgNPs by varying the concentration of silver nitrate and the amount of extract. Leaf extract is made by dissolving 10 grams of dried leaf powder in 100 ml double-distilled water (DDW). The concentration of silver nitrate was variable by 1,5, 10 mM with different amounts of leaf extract. The UV-Vis absorption spectrum of colloid in the range between 439-453 nm confirmed that AgNPs have been successfully synthesized. FT-IR absorption band shows the feasible biomolecules of Rhizophora stylosa responsible for the production of silver nanoparticles were amine, alcohol, phenol, alkyl halide, and aromatic combinations groups. The XRD pattern regulates that the synthesized AgNPs were in a face-centered cubic (fcc) crystal structure with an average size of 25 nm. TEM images informed that the synthesized AgNPs have a spherical shape with a size range between 9 to 57 nm. The average size of the nanoparticles was 30 nm. The solution of stable silver nanoparticle colloid from 1 until 3-month incubation. AgNPs have good antibacterial and antioxidant activity compared to pure plant extract. [ABSTRACT FROM AUTHOR]