Abstract
Synthesizing nanoparticles with the less environmentally malignant approach using plant extract is of great interest; this is because most of the chemical approaches can be very costly, toxic, and time-consuming. Herein, we report the use of Acacia senegal leaf extracts to synthesize silver nanoparticles (AgNPs) using an environmentally greener approach. Silver ions were reduced using the bioactive components of the plant extracts with observable colour change from faint colourless to a brownish solution as indication of AgNP formation. The structural properties of the as-synthesized AgNPs were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV-Vis absorption spectrum. Antimicrobial assessment of the as-synthesized AgNPs was explored on some strains of gram-positive and gram-negative bacteria. The obtained results indicate that the as-synthesized AgNPs are pure crystallite of cubic phase of AgNPs, fairly dispersed with a size range of 10–19 nm. The AgNPs were found to be small in size and exhibit significant antibacterial activities, suggesting that the as-synthesized AgNPs could be used in the pharmaceutical and food industries as bactericidal agents.
Highlights
The biosynthetic approach in the use of naturally occurring reducing agents such as plant extracts, biomass, and biological molecules has emerged as a simple alternative method to complex chemical method of nanoparticle synthesis
The AgNPs obtained from the Acacia senegal aqueous extract had very strong inhibitory action against some selected grampositive and gram-negative bacteria, and their zone of inhibition and Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) in μg/L are presented in Tables 2 and 3
Among the gram-positive bacteria (Table 2), B. cereus had the highest inhibitory activity followed by S. agalactiae, S. aureus, E. faecalis, and E. gallinarum, respectively
Summary
The biosynthetic approach in the use of naturally occurring reducing agents such as plant extracts, biomass, and biological molecules has emerged as a simple alternative method to complex chemical method of nanoparticle synthesis. Silver nanoparticles were synthesized from aqueous leaf extracts of Acacia senegal (Gum Arabic), a plant that grows in a number of sub-Saharan African countries like Sudan, Nigeria, Mauritania, Senegal, Mali, Burkina Faso, Niger, Chad, Cameroon, Somalia, Ethiopia, and Kenya [32,33,34] This plant is mainly known for the rich gummy exudate produced by its stem and branches, which is a nonviscous liquid rich in soluble fibres [32, 35, 36]. The bioactive components of the Acacia senegal leaf extracts have been previously analyzed and found to contain compounds like phenols, flavonoid, alkaloid, saponins, tannins, and terpenoids [37] These compounds are known to act as reducing agents in the synthesis of metal nanoparticles [38, 39]. We used the leaf extracts of the Acacia senegal plant both as reducing and capping agent during the synthesis of silver nanoparticles (AgNPs) in distilled water and the resulting nanoparticles were tested for their antimicrobial activity on selected gram-negative and grampositive bacteria
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