Green route to synthesize Zinc Oxide Nanoparticles using leaf extracts of Cassia fistula and Melia azadarach and their antibacterial potential

Minha Naseer,Bin Chen,Bushra Khalid,Usman Aslam

doi:10.1038/s41598-020-65949-3

Abstract

Development of plant based nanoparticles has many advantages over conventional physico-chemical methods and has various applications in medicine and biology. In present study, zinc oxide (ZnO) nanoparticles (NPs) were synthesized using leaf extracts of two medicinal plants Cassia fistula and Melia azadarach. 0.01 M zinc acetate dihydrate was used as a precursor in leaf extracts of respective plants for NPs synthesis. The structural and optical properties of NPs were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), ultraviolet-visible spectrophotometer (UV-Vis) and dynamic light scattering (DLS). The antibacterial potential of ZnO NPs was examined by paper disc diffusion method against two clinical strains of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) based on the zone of inhibition and minimal inhibitory indices (MIC). Change in color of the reaction mixture from brown to white indicated the formation of ZnO NPs. UV peaks at 320 nm and 324 nm, and XRD pattern matching that of JCPDS card for ZnO confirmed the presence of pure ZnO NPs. FTIR further confirmed the presence of bioactive functional groups involved in the reduction of bulk zinc acetate to ZnO NPs. SEM analysis displayed the shape of NPs to be spherical whereas DLS showed their size range from 3 to 68 nm. The C. fistula and M. azadarach mediated ZnO NPs showed strong antimicrobial activity against clinical pathogens compared to standard drugs, suggesting that plant based synthesis of NPs can be an excellent strategy to develop versatile and eco-friendly biomedical products.

Highlights

Plant mediated synthesis of nanoparticles (NPs) is a revolutionary technique that has wide range of applications in agriculture, food industry and medicine
zinc oxide (ZnO) NPs synthesized by using leaf extracts of Passiflora caerulea, Scadoxus multiflorus and Camellia sinensis showed strong antimicrobial efficacy against Klebsiella pneumonia, Aspergillus spp., and Staphylococcus aureus and Pseudomonas aeruginosa respectively[16,17,18], suggesting that medicinal plant extract mediated synthesis of ZnO NPs can be very useful for medical industry
We use a relatively higher temperature of 70 °C for incubating the reactants that leads to the production of very small sized ZnO NPs

Summary

Introduction

Plant mediated synthesis of nanoparticles (NPs) is a revolutionary technique that has wide range of applications in agriculture, food industry and medicine. Plants possess rich genetic variability with respect to number of biomolecules and metabolites like proteins, vitamins, coenzymes based intermediates, phenols, flavonoids and carbohydrates These plant metabolites contain hydroxyl, carbonyl, and amine functional groups that react with metal ions and reduce their size into nano range. Flavonoids contain several functional groups and it is believed that -OH group of flavonoids is mainly considered responsible for the reduction of metal ions into NPs4 These molecules help in bioreduction of the ions to the nano scale size, but they play a pivotal role in the capping of the nanoparticles which is important for stability and biocompatibility[5]. Leaves of C. fistula contain a wide variety of antioxidants for example; terpenoids, flavonoids, alkaloids, phenolic compounds, tannins, saponins, anthocyanosides, carbohydrates, proteins, steroids, cardiac glycosides and phlobatannins[20]

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Conclusion