Characterisation and Evaluation of Antimicrobial, Antioxidant and Antibiofilm Activities of Silver Nanoparticles Biosynthesised from Harpullia arborea Bark Extract

Abstract

Introduction: In recent years, plant-based antibacterial substance has replaced the conventional chemical synthesis method. Harpullia arborea belongs to the Sapindaceae family; its bark, fruit, and seeds are used by Indians as leech repellent, hair wash, and antirheumatic agents. Plant-mediated green synthesis of nanomaterials is gaining popularity due to its environmental friendliness and cost-effectiveness. Aim: To synthesise Silver Nanoparticles (AgNPs) using bark extract of Harpullia arborea and evaluate their antibacterial efficacy against food borne pathogens. Materials and Methods: The in-vitro study of antimicrobial activity of Harpullia arborea bark extract was utilised for the synthesis of nanoparticles with 2 mM of silver nitrate. The study was conducted from March 2017 to April 2017. The synthesised nanoparticles were confirmed and characterised using Ultraviolet-Visible (UV-Vis) spectroscopy, while Fourier transform infrared, and electron microscopy were utilised for the determination of shape and size of the synthesised particle. The synthesised AgNPs were subjected to antibacterial activity against food isolates using agar well diffusion method. Furthermore, Minimal Inhibitory Concentration (MIC) and antioxidant were also measured with titre plate and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) method, respectively. Results: The UV-Vis spectra showed conformation of AgNPs with surface resonance peak of 430 nm, and Fourier-transform Infrared Spectroscopy (FTIR) spectra confirmed the involvement of biological molecules in AgNPs synthesis. In addition, Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) analysis confirmed AgNPs with a spherical shape with diameters from 26.3-40.6 nm. The well diffusion method showed the antibacterial activity of AgNPs against bacterial isolates. The results showed that AgNPs possess higher antimicrobial potency than non AgNPs. The lowest Minimum Inhibitory Concentration (MIC) was observed against Staphylococcus aureus [3.5 mg] and followed by Enterococcus faecalis and Pseudomonas aeruginosa (4.5 mg). The DPPH method has confirmed that silver nanoparticles have a similar antioxidant activity compared to ascorbic acid. Conclusion: It can be concluded that Harpullia arborea bark extract can be used effectively in the production of potent antimicrobial and antioxidants for commercial use.

Keywords

• energy dispersive x-ray
• scanning electron microscopy
• transmission electron microscopy