Abstract
Biosynthesized silver nanoparticles (AgNPs) are widely used in Pharmacy and Medicine. In particular, AgNPs synthesized and mediated by plant extracts have shown topossess several biological activities. In the present study, AgNPs were synthesized using Picea abies L. stem bark extract as reducing agent. Factors, such as metal ion solution, pH, and time, which play a role in the AgNPs synthesis, were assessed. The synthesized AgNPs were characterized by Ultraviolet-Visible Spectrometry, Fourier transform infrared spectroscopy, and Transmission Electron Microscopy (TEM). Further, the study has been extended to evaluate the antimicrobial and antioxidant activity of AgNPs. The broad peak obtained at 411–475 nm (UV-Vis spectroscopy), and the color change pattern, confirmed the synthesis of AgNPs. TEM results showed spherical or rarely polygonal AgNPs with an average size of 44 nm at pH = 9. The AgNPs showed antioxidant activity and antibacterial effect against human pathogenic Gram-positive and Gram-negative bacteria. The results show that spruce bark extract is suitable for obtaining AgNPs, with antibacterial and antioxidant activity.
Highlights
The bark of woody vascular plants has an essential role in plant protection [1,2]
The total polyphenol content (TPC) of the filtered extract was assessed based on the gallic acid calibration curve, the final results being expressed in mg GAE/g biomass
[22], while lower wavelengths indicate a decrease of their diameter [23]. These results suggest a significant number of smaller diameter AgNPs when synthesis was driven at pH = 9, and show that AgNPs are present in the colloidal dispersion, stabilized by the bio-compounds from spruce bark extract [24]
Summary
The bark of woody vascular plants has an essential role in plant protection [1,2]. The bark is considered to be a forest waste. The main biomolecules identified in spruce bark extract are catechin, vanillic acid, gallic acid isorhapontin, piceid, and astringin [4,8] These compounds are valuable for their antioxidant and antibacterial activity [5,8]. In another study coordinated by Patil et al [13], AgNPs were synthesized from Lantana camara leaves They showed significant antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, compared to the standard Ciprofloxacin. The results were compared with the antibacterial activity of the petroleum ether extract and the essential oil isolated from the Lantana camara L. leaves. The antibacterial activity of AgNPs was higher compared to the petroleum ether extract and the essential oil of the leaves of L. camara L., showing that AgNPs have dose-dependent membrane permeability. Based on the literature data, the main objectives of the current study are: Biosynthesis of AgNPs using polyphenolic spruce bark extract (SBE), with a previously developed technique [14,15]; the determination of the influence of different factors on the biosynthesis processes (metallic salt, time and pH); the characterization of biosynthesized AgNPs by specific assays: Ultraviolet-Visible Spectrometry (UV-Vis), Fourier transforms infrared spectroscopy (FTIR), and Transmission Electron Microscopy (TEM); and the evaluation of antioxidant and antibacterial activity for biosynthesized AgNPs
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