Biosynthesis of Silver Nanoparticles Using Salvia pratensis L. Aerial Part and Root Extracts: Bioactivity, Biocompatibility, and Catalytic Potential

Abstract

The aim of this research was the synthesis of silver nanoparticles (SPA- and SPR-AgNPs) using the aqueous extracts of the aerial (SPA) and the root (SPR) parts of the plant Salvia pratensis L., their characterization, reaction condition optimization, and evaluation of their biological and catalytic activity. UV-Vis spectroscopy, X-ray powder diffraction (XRPD), scanning electron microscopy with EDS analysis (SEM/EDS), and dynamic light scattering (DLS) analysis were utilized to characterize the nanoparticles, while Fourier transform infrared (FTIR) spectroscopy was used to detect some functional groups of compounds present in the plant extracts and nanoparticles. The phenolic and flavonoid contents, as well as the antioxidant activity of the extracts, were determined spectrophotometrically. The synthesized nanoparticles showed twice-higher activity in neutralizing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) compared with the respective extracts. SPR-AgNPs exhibited strong antimicrobial activity against almost all of the tested bacteria (<0.0039 mg/mL) and fungal strains, especially against the genus Penicillium (<0.0391 mg/mL). Moreover, they were fully biocompatible on all the tested eukaryotic cells, while the hemolysis of erythrocytes was not observed at the highest tested concentration of 150 µg/mL. The catalytic activity of nanoparticles toward Congo Red and 4-nitrophenol was also demonstrated. The obtained results confirm the possibility of the safe application of the synthesized nanoparticles in medicine and as a catalyst in various processes.

Keywords: Salvia pratensis L.; antimicrobial activity; antioxidant activity; catalysts; hemolytic activity; silver nanoparticles.

Figure 1

Influence of different parameters on the synthesis of SPA-AgNPs. (A) Extract concentrations, (B) AgNO₃ concentrations, (C) pH value, and (D) temperature.

Figure 2

Influences of different parameters on the synthesis of SPR-AgNPs. (A) Extract concentrations, (B) AgNO₃ concentrations, (C) pH value, and (D) temperature.

Figure 3

Time-dependent UV–Vis absorption spectra of (A) SPA-AgNPs and (B) SPR-AgNPs obtained under the optimal conditions.

Figure 4

Characterization of AgNPs synthesized using S. pratensis extracts using various analytical techniques. XRPD spectrum of (A) SPA-AgNPs and (B) SPR-AgNPs; SEM images of (C) SPA-AgNPs and (D) SPR-AgNPs and their corresponding EDS spectra ((E) and (F), respectively).

Figure 5

FTIR spectra of the S. pratensis aerial part (A) and root (B) extracts and corresponding AgNPs. (C) Size distribution of SPA-AgNPs and SPR-AgNPs by DLS analysis.

Figure 6

Effect of SPA-AgNPs and SPR-AgNPs on the viability of immortalized cells and cancer cells. Increasing concentrations (1–200 μg/mL) of SPA-AgNP (A,B) or SPR-AgNP (C,D) nanoparticles were added to HaCaT (black circles), BALB/c-3T3 (black triangles), A431 (empty squares), or SVT2 (empty rhombuses) for 72 h. Cell viability was assessed by the MTT assay and cell survival was expressed as a percentage of viable cells in the presence of the nanoparticle under test with respect to the control cells grown in the absence of the nanoparticle. The data shown represent the means ± S.D. of three independent experiments.

Figure 7

UV–Vis spectra of the catalytic degradation of Congo Red (A) and 4-nitrophenol (B) in the presence of NaBH₄ without AgNPs. Catalytic degradation of Congo Red in the presence of SPA-AgNPs (C) and SPR-AgNPs (E). Catalytic degradation of 4-nitrophenol in the presence of SPA-AgNPs (D) and SPR-AgNPs (F). The best fitted chemical kinetic linear model (zero-order) for Congo Red (G) and 4-nitrophenol (H) degradation using synthetized AgNPs and NaBH₄.