Investigation of In Vitro Antioxidant and Antibacterial Potential of Silver Nanoparticles Obtained by Biosynthesis Using Beech Bark Extract

Abstract

Green synthesis is one of the rapid and best ways for silver nanoparticles (AgNP) synthesis. In the present study, synthesis and bioactivity of AgNPs has been demonstrated using water beech (Fagus sylvatica L.) bark extract. The physical and chemical factors such as time, metal ion solution, and pH, which play a vital role in the AgNPs synthesis, were assessed. The AgNPs were characterized by ultraviolet-visible (UV-Vis) spectrometry, Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). Antioxidant and antimicrobial activity of the obtained AgNPs was evaluated. AgNPs were characterized by color change pattern, and the broad peak obtained at 420-475 nm with UV-Vis confirmed the synthesis of AgNPs. FT-IR results confirmed that phenols and proteins of beech bark extract are mainly responsible for capping and stabilization of synthesized AgNPs. TEM micrographs showed spherical or rarely polygonal and triangular particles with an average size of 32 nm at pH = 9, and 62 nm at pH = 4. Furthermore, synthesized AgNPs were found to exhibit antioxidant activity and have antibacterial effect against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, and Pseudomonas aeruginosa. These results indicate that bark extract of F. sylvatica L. is suitable for synthesizing stable AgNPs, which act as an excellent antimicrobial agent.

Keywords: antibacterial; antioxidant; beech bark; polyphenols; silver nanoparticles.

Figure 1

Color transformation of beech bark extract solution with AgNO₃ at pH = 4 (test solution 1 (TS1)) and pH = 9 (TS2).

Figure 2

UV–visible absorption spectra of synthesized silver nanoparticles using tested solutions: (a) TS1—beech bark extract, pH = 4, AgNO₃; (b) TS2—beech bark extract, pH = 9, AgNO₃; (c) TS3—beech bark extract, pH = 4, AgC₂H₃O₂; (d) TS4—beech bark extract, pH = 9, AgC₂H₃O₂.

Figure 3

Fourier transform infrared spectra of aqueous bark extract.

Figure 4

Fourier transform infrared spectra of gold nanoparticles (AgNPs): A—TS2 (AgNPs obtained with AgNO₃ at pH = 9), B—aqueous bark extract, C—TS1 (AgNPs obtained with AgNO₃ at pH = 4).

Figure 5

Graphical representation of AgNPs synthesized in the presence of the extract obtained from the beech bark and AgC₂H₃O₂: (a) TS3— TEM photomicrograph; (b) histogram of the distribution of AgNP size distribution in TS3; (c) TS4—TEM image; (d) histogram of the distribution of AgNP size distribution in TS4. (TS3—beech bark extract, pH = 4, AgC₂H₃O₂; TS4—beech bark extract, pH = 9, AgC₂H₃O₂).

Figure 6

Graphical representation of AgNP synthesized in the presence of the extract obtained from the beech bark and AgNO₃: (a) TS1— TEM photomicrograph; (b) histogram of the distribution of the AgNP size distribution in the TS1; (c) TS2—TEM image; (d) histogram of the distribution of AgNP size distribution in TS2 (TS1—beech bark extract, pH = 4, AgNO₃; TS2—beech bark extract, pH = 9, AgNO₃).

Figure 6

Graphical representation of AgNP synthesized in the presence of the extract obtained from the beech bark and AgNO₃: (a) TS1— TEM photomicrograph; (b) histogram of the distribution of the AgNP size distribution in the TS1; (c) TS2—TEM image; (d) histogram of the distribution of AgNP size distribution in TS2 (TS1—beech bark extract, pH = 4, AgNO₃; TS2—beech bark extract, pH = 9, AgNO₃).

Figure 7

Graphical and visual representation of the growth rate for S. aureus (A,D), E. coli (B,E), P. aeruginosa (C,F) in the presence of TS4 (beech extract + AgC₂H₃O₂ pH = 9) and in the absence of TS4 (Control) at: initial time—H0, 3 h—H1, and 6 h—H2.