Synthesis of silver and copper oxide nanoparticles using Myristica fragrans fruit extract: Antimicrobial and catalytic applications

Highlights

• Green synthesis of copper oxide and silver nanoparticles using Myristica fragrans fruit extract.

• Enhanced application of the less economic pericarp of an industrially important plant Myristica fragrans.

• Well characterisation of the nanoparticles synthesized.

• Application of the copper nanoparticles as a catalyst for click synthesis of 1,2,3-triazoles.

• Application of the silver nanoparticles as antibacterial agent.

Abstract

The pericarp of Myristica fragrans fruit extract was utilized for a low cost, eco-friendly synthesis of silver (AgNPs) and copper oxide (CuONPs) nanoparticles. The aqueous fruit extract of the plant was used as reducing and stabilizing agents for this preparation. Characterization of the biosynthesized nanoparticles was carried out using UV–Vis spectroscopy, FTIR spectroscopy and X-Ray Diffraction studies. Morphology and size of the particles was observed using Field-Emission Scanning Electron Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM). The copper and silver nanoparticles show Surface Plasmon Resonance (SPR) band at 360 and 478 nm respectively in the UV–Vis spectrum. It was observed that size of the synthesized copper oxide and silver nanoparticles are in the range 10–50 nm. The presence of copper and silver elements was confirmed from their respective EDS spectrum. Involvement of phytochemicals in the stabilization and reduction of the nanoparticles was confirmed by FTIR spectroscopy. CuONPs exhibited catalytic activity in 1,3-dipolar cycloaddition reaction between azides and terminal alkynes to form 1,2,3-triazoles. Silver nanoparticle possesses good antibacterial activity against multidrug human pathogens Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis. The present study focuses on the utilization of the less economic part of Myristica fragrans fruit's pericarp for the preparation of copper oxide and silver nanoparticles which have good catalytic and antibacterial activities.

Introduction

For the last two decades, nanomaterials have gained much attention due to their interesting properties that can be attributed to the change in geometry, size, shape, and morphology when compared with bulk materials (Thangavel and Ramaraj, 2008; Nadagouda and Varma, 2006). Moreover, nanotechnology and natural science offer diverse and easy biosynthetic pathways that can extend the application of nanoparticles in catalysis, pollution control, agriculture, waste management, and in the biomedical field as antimicrobial, anticancer agents (Lewinski et al., 2008). Among the metal nanoparticles, copper and silver nanoparticles are comparatively more important due to their wide range of applications in biology (Nasrollahzadeh et al., 2019a, Nasrollahzadeh et al., 2019b). They are known to have a broad range of antimicrobial properties and most of them are not detrimental to human health (Koduru et al., 2018). Biosynthesis of nanoparticles is generally a bottom-up approach involving reduction and oxidation reactions which utilise plant extracts, bacteria, fungi as raw materials (Hebbalalu et al., 2013). Although the exact synthetic mechanism is still unknown, synthesis of nanoparticles requires the presence of reducing and stabilizing agents where the organic molecules are able to handle both the roles. Metal oxide nanoparticle possesses exclusive chemical and physical properties because of their high density and surface area. Developing environmentally benign methods for the synthesis of metal nanoparticles relies on the utilization of non toxic chemicals (Anastas and Kirchhoff, 2002). Use of microwave has emerged as an effective tool in synthesis of nanoparticles in aqueous media (Baruwati et al., 2009; Kou and Varma, 2012). Such green chemistry protocols protect the environment by reducing waste by utilizing renewable sources and energy efficiency (Baruwati and Varma, 2009).

Plant extract mediated synthesis of nanoparticles has been copiously reported in the recently. (Saratale et al., 2018). Nanoparticles have been synthesized from bio-resources utilizing the rich reservoir of alkaloids and flavonoids present in it (Nadagouda and Varma, 2008; Nadagouda et al., 2014). Such green nanoparticle synthesis is simple and possesses innumerable applications (Varma, 2012; Abdelghany et al., 2018). Biological applications of such nanoparticles include their potential cytotoxicity towards different cancerous cells (Jadhav et al., 2018a, Jadhav et al., 2018b), antimicrobial power (Zheng et al., 2018), antioxidant, DNA cleavage properties (Jadhav et al., 2018a, Jadhav et al., 2018b) and anticoagulant capacity (Tian et al., 2014). Metal oxide nanoparticle found out its application in optoelectronics (Yu et al., 2016), sensors (Cho et al., 2017) and in fuel cells (Sun et al., 2019). They have been also used in biomedical and environmental sensors (Belushkin et al., 2018). In addition to the above applications, silver nanoparticles are widely used in degradation of dyes (Polepalli and Rao, 2018) and in mosquito control (Sooresh et al., 2011). However, there are only a few reports on the catalytic activity of nanoparticles synthesized using plant materials (Xia et al., 2013; Nasrollahzadeh et al., 2019a, Nasrollahzadeh et al., 2019b).

Conventionally, Husigen's 1,3-dipolar cycloaddition reaction between azide and alkyne was utilized for the construction of triazole ring. This uncatalyzed reaction required high temperature but was slow in nature affording both 1,4- and 1,5-disubstituted triazoles in equal amounts (Huisgen, 1963). Introduction of copper (I) species as a catalyst for the regioselective synthesis of the 1,4-isomer has received wide attention after the work of Sharpless (Kolb et al., 2001), who coined the term Click Chemistry. It has a wide range of applications in organic chemistry (Bock et al., 2006; Meldal et al., 2017), medicinal chemistry (Anseth and Klok, 2016), polymers, material sciences (Lutz, 2007) and bioconjugation (Lutz and Zarafshani, 2008). Development of new synthetic protocols using principles of green chemistry are much sought after. In this context, green synthesis of metal nanoparticles using biosources has been suggested.

Myristica fragrans belongs to the family Myristicaceae, the source of the spices nutmeg and mace. Outer pericarp of the fruit possesses little commercial value and is usually thrown away after extracting the seed and aril. Myristica fragrans fruit is used for the treatment of digestive disorders in traditional medicines (Acuña et al., 2016). Its extract possesses antioxidant and anti-inflammatory properties and has been widely used in food industry (e.g., jam, pickle, cake, and jelly) and in beverage preparations (Sulaiman and Ooi, 2012). The pharmacological evaluation reveals that aqueous extract of the pericarp contains terpenoids, flavones, phenols, tannins, sugars etc. (Zhao et al., 2019; Pandey et al., 2016). In the present study, extract of the pericarp was used for preparing copper oxide and silver nanoparticles. The synthesized nanoparticles were well characterized. Further, the efficiency of copper oxide nanoparticle towards catalyzing the click reaction for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles and antimicrobial activity of the silver nanoparticle by disc diffusion method was investigated.