Silver nanoparticle synthesis by Acalypha wilkesiana extract: phytochemical screening, characterization, influence of operational parameters, and preliminary antibacterial testing

Adewumi Oluwasogo Dada; Folahan Amoo Adekola; Fehintoluwa Elizabeth Dada; Adunola Tabitha Adelani-Akande; Micheal Oluwasesan Bello; Chidiogo Rita Okonkwo; Adejumoke Abosede Inyinbor; Abimbola Peter Oluyori; Adeniyi Olayanju; Kolawole Oluseyi Ajanaku; Charles Oluwaseun Adetunji

doi:10.1016/j.heliyon.2019.e02517

Silver nanoparticle synthesis by Acalypha wilkesiana extract: phytochemical screening, characterization, influence of operational parameters, and preliminary antibacterial testing

Heliyon. 2019 Oct 2;5(10):e02517. doi: 10.1016/j.heliyon.2019.e02517. eCollection 2019 Oct.

Affiliations

¹ Industrial Chemistry Programme, Nanotechnology Laboratory, Department of Physical Sciences, (Science and Technology Research Cluster), College of Pure and Applied Sciences, Landmark University, P.M.B.1001, Omu-Aran, Kwara State, Nigeria.
² Department of Industrial Chemistry, University of Ilorin, P.M.B 1515, Unilorin, Nigeria.
³ School of Postgraduate Studies, Landmark University, P.M.B.1001, Omu-Aran, Kwara State, Nigeria.
⁴ Department of Biological Sciences, Microbiology Programme, Landmark University, Omu-Aran, Nigeria.
⁵ National Center for Natural Products Research, School of Pharmacy, The University of Mississippi, Oxford, MS, USA.
⁶ Department of Applied Chemistry, Federal University Dutsin-Ma, Katsina State, Nigeria.
⁷ Department of Agricultural and Biosystems Engineering, College of Engineering, Landmark University, P.M.B.1001, Omu-Aran, Kwara State, Nigeria.
⁸ Department of Chemistry, Covenant University, P.M.B. 1023, Ota, Ogun State, Nigeria.
⁹ Jawaharlal Nehru University, School of Life Sciences, Laboratory of Genetic Manipulation for Stress Alleviation and Value Addition in Plants, New Delhi, 110067, India.

Abstract

Single pot green synthesis of silver nanoparticles (AgNPs) was successfully carried out using medicinal plant extract of Acalypha wilkesiana via bottom-up approach. Five imperative operational parameters (pH, contact time, concentration, volume ratio and temperature) pivotal to the synthesis of silver nanoparticles were investigated. The study showed pH 9, 90 min contact time, 0.001 M Ag⁺ concentration, volume ratio 1:9 (extract: Ag⁺ solution), and temperature between 90 - 100 °C were important for the synthesis of Acalypha wilkesiana silver nanoparticles (AW-AgNPs). Phytochemical screening confirmed the presence of saponins, flavonoids, phenols and triterpenes for A. wilkesiana. These phytomolecules served as both capping and stabilizing agent in the green synthesis of silver nanoparticles. AW-AgNPs was characterized by UV-Vis Spectroscopy, Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX). The surface Plasmon resonance (SPR) was observed at 450 nm which is a characteristic absorbance region of AW-AgNPs formation as a result of the collective oscillation of free electron of silver nanoparticles. FTIR Spectroscopy confirmed the presence of functional groups responsible for bioreduction of Ag⁺. SEM and TEM results confirmed a well dispersed AW-AgNPs of spherical shape. EDX shows the elemental distribution and confirmed AgNPs with a characteristic intense peak at 3.0 keV. AW-AgNPs showed significant inhibition against selected Gram negative and Gram positive prevailing bacteria. AW-AgNPs can therefore be recommended as potential antimicrobial and therapeutic agent against multidrug resistant pathogens.

Keywords: Acalypha wilkesia; Analytical chemistry; Antimicrobial studies; Biotechnology; Environmental health; Materials chemistry; Nanomaterials; Operational parameters; Organic chemistry; Pharmaceutical chemistry; Pharmaceutical science; Pharmacology; Physical chemistry; Silver nanoparticles.