Coconut inflorescence sap mediated synthesis of silver nanoparticles and its diverse antimicrobial properties

Abstract

Green synthesis of nanoparticles (NPs) involves the use of diverse extracts of biological origin as substrates to synthesize nanoparticles and can overcome the hazards associated with chemical 2 methods. Coconut inflorescence sap, which is unfermented phloem sap obtained by tapping of coconut inflorescence, is a rich source of sugars and secondary metabolites. In this study, coconut inflorescence sap was used to synthesize silver nanoparticles (AgNPs). We have initially undertaken metabolomic profiling of coconut inflorescence sap from West Coast Tall cultivar to delineate its individual components. Secondary metabolites constituted the major portion of the inflorescence sap along with sugars, lipids and, peptides. The concentration of silver nitrate, inflorescence sap and incubation temperature for synthesis of AgNPs were optimized. Incubating the reaction mixture at 40ºC was found to enhance AgNP synthesis. The AgNPs synthesized were characterized using UV-Visible spectrophotometry, X-Ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). Antimicrobial property of AgNP was tested in tissue culture of arecanut (Areca catechu L.) where bacterial contamination (Bacillus pumilus) was a frequent occurrence. Significant reduction in the contamination was observed when plantlets were treated with aqueous solutions of 0.01, 0.02 and 0.03% of AgNPs for one hour. Notably, treatment with AgNPs did not affect growth and development of the arecanut plantlets. Cytotoxicity of AgNPs was quantified in HeLa cells. Viability (%) of HeLa cells declined significantly at 10 ppm concentration of AgNP and complete mortality was observed at 60 ppm. Antimicrobial properties of AgNPs synthesized from inflorescence sap were also evaluated and confirmed in human pathogenic bacteria viz., Salmonella sp., Vibrio parahaemolyticus, and Escherichia coli. The study concludes that unfermented inflorescence sap, with above neutral pH, serves as an excellent reducing agent to synthesize AgNPs from Ag+.3

Antimicrobial and antioxidant potential of the silver nanoparticles synthesized using aqueous extracts of coconut meat (Cocos nucifera L)

“…The data presented is an average calculation of 200 particles (Image J software) plotted by Origen Pro. Silver nanoparticles synthesized from coconut inflorescence sap and leaf extracts measured between 10 and 30 nm, which is in perfect agreement with the present study 72 , 75 . The average size measured by the zeta sizer showed low PDI but larger particles in comparison to TEM measurements due to the fact that DLS measurements are taken in a liquid state (solution) and include the size of the metallic core, phytochemicals (coatings), and the layer of solution, unlike TEM measurements, which measure solely the metallic core 76 .…”

“…Previous studies have reported similar variations in peak positions 10 , 71 . The FTIR spectra of AgNPs synthesized using coconut inflorescence sap surprisingly showed peaks in similar positions (2990 cm −1 , 2912 cm −1 , 1100 cm −1 ); these peaks were attributed to CH 2 stretching vibration of the pyrrole ring and C–C–CH 2 linkage of a long carbon 71 , 72 . Earlier studies have reported coconut meat and coconut water as rich sources of dietary fibers, proteins, amino acids, and alkaloids, which authenticates the present findings 73 , 74 .…”

Biosynthesis of phyto-functionalized silver nanoparticles using olive fruit extract and evaluation of their antibacterial and antioxidant properties

“…The main bioactive compounds present in olive fruit (OF) are phytochemicals including flavonoids, phenolic acids, terpenoids, phenolic alcohols, sugars, proteins, alkaloids, secoiridoids, and hydroxycinnamic acid derivatives ( Ghanbari et al, 2012 ), which can act as reducing agents, stabilizers, and capping agents during nanoparticle synthesis. Natural antioxidants extracted from plants, especially phenolics and flavonoids ( e.g ., ferulic acid, gallic acid, kaempferol, quercetin, and catechins), have been examined as antioxidant-based antibacterial agents and demonstrated promising effects to overcome the resistance of various microbes versus synthetic antibiotics ( Rajesh et al, 2020 ). Additionally, when combined with silver nanoparticles, plant extracts can exhibit synergistic effects, enhancing their antibacterial activity and colloidal stability compared to other traditional capping agents and biomolecules ( Some et al, 2020 ).…”

Biocompatible CuInS2 Nanoparticles as Potential Antimicrobial, Antioxidant, and Cytotoxic Agents

“…A study shows the good biocompatibility stability of Gd-based CIS/ZnS nanoprobes for in vitro cytotoxicity . The literature states that the incorporation of plant extracts such as Azadirachta indica (neem), , Ocimum sanctum (basil), , Cocos nucifera (coconut), Aloe vera (aloe), , Curcuma longa (turmeric), and so forth during synthesis makes the NPs biocompatible. The incorporation of green extracts improves the antimicrobial, antioxidant, and cytotoxicity activities of the NPs. − Apprehending the significance of CIS NPs, the authors decided to study them for biological applications.…”