Green synthesis and antibacterial studies of Saponin-mediated AgNPs using resin extracts of the Commiphora myrrha medicinal plant
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Date
2024
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University of the Western Cape
Abstract
Nanoscience, particularly the use of silver nanoparticles (AgNPs), has transformed numerous sectors due to their unique properties. However, traditional synthesis methods for AgNPs raise environmental and biocompatibility concerns, prompting the development of green synthesis approaches. This study investigates the green synthesis of AgNPs using saponin-rich extracts from the resin of Commiphora myrrha, an eco-friendly and sustainable strategy that leverages natural resources to advance green nanotechnology.
Saponin-rich resin extracts from C. Myrrha were fractionated into four distinct extracts—designated as H (high molecular weight carbohydrates), O (organic soluble compounds), L (low molecular weight carbohydrates), and E (ethanol soluble compounds)—to synthesize corresponding Saponin-AgNPs (H-AgNPs, O-AgNPs, L-AgNPs, and E-AgNPs). The work’s novelty lies in linking the unique chemical profiles of these extracts to NP yield, stability, and functionality under optimized synthesis conditions. Preliminary phytochemical screening of the extracts was performed using thin-layer chromatography (TLC), liquid chromatography-mass spectroscopy (LC-MS), and Fourier transform-infrared spectroscopy (FT-IR), confirming the presence of saponins which served as reducing and stabilizing agents during NP synthesis. The synthesized AgNPs were characterized using ultraviolet-visible spectroscopy (UV-Vis), (FT-IR), inductively coupled plasma-optical emission spectroscopy (ICP-OES), dynamic light scattering (DLS), high resolution-scanning electron microscopy (HR-SEM), high resolution-transmission electron microscopy (HR-TEM), and energy-dispersive x-ray spectroscopy (EDX). Stability tests were conducted after six months.
The synthesis parameters were tailored to the unique chemical compositions of the extracts, which influenced their reducing and stabilizing capabilities. For instance, H-AgNPs were synthesized at pH 11, a reaction temperature of 90°C, an extract concentration of 3.1250 mg/mL, an AgNO₃ concentration of 5 mM, and a 1:2 extract-to-silver salt ratio, under a rotation speed of 1000 rpm for 12 hours. O-AgNPs, by contrast, required pH 7, a reaction temperature of 90°C, an extract concentration of 25.0000 mg/mL, a silver nitrate (AgNO₃) concentration of 2 mM, and a 1:9 extract-to-silver salt ratio, under a rotation speed of 500 rpm for 1 hour. These tailored conditions maximized nanoparticle (NP) yield, stability, and functionality for each extract. While H-AgNPs demonstrated superior stability after six months, the differences in synthesis parameters complicate direct comparisons. Future studies could investigate synthesis under identical conditions for improved comparative analysis.
HR-TEM revealed spherical NPs with crystallite sizes of 6.38 ± 0.5 nm (H-AgNPs), 8.19 ± 0.7 nm (O-AgNPs), 7.29 ± 0.6 nm (L-AgNPs), and 9.96 ± 0.8 nm (E-AgNPs). ICP-OES analysis indicated that O-AgNPs had the highest silver content (96.72 ppm), while DLS data showed the smallest hydrodynamic radii for L-AgNPs (333.1 nm). Antibacterial activity was assessed against Escherichia coli (E. Coli), methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus aureus (S. Aureus), and Pseudomonas aeruginosa (P. Aeruginosa) using agar well diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) tests. E-AgNPs displayed the strongest antibacterial activity, with a MIC of 22 μg/mL against S. Aureus, while O-AgNPs showed the weakest activity (MIC = 61 μg/mL). This study successfully achieved its objectives, demonstrating that green synthesis using C. Myrrha resin extracts is a viable and eco-friendly alternative to conventional methods. By elucidating the relationship between extract composition, synthesis conditions, and NP properties, the research provides valuable insights for advancing green nanotechnology, particularly in biomedicine and sustainable materials science.
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Keywords
Green synthesis, C. Myrrha, Saponin-rich extracts, AgNPs, Antibacterial activity