Biological Evaluation of Silver Nanoparticles Obtained from T. arjuna Bark Extract as Both Reducing and Capping Agent

Terminalia arjuna, a Cardioprotective Herbal Medicine-Relevancy in the Modern Era of Pharmaceuticals and Green Nanomedicine-A Review

Herbal medicines were the main source of therapeutic agents in the ancestral era. Terminalia arjuna (TA) is one such medicinal plant widely known for its several medicinal properties, especially its cardiovascular properties. They have several phytochemicals, such as flavonoids, polyphenols, triterpenoids, tannins, glycosides, and several minerals, proteins, and others that are responsible for the above-mentioned medicinal properties. In this review, we have first elaborated on the various processes and their parameters for the efficient extraction of relevant phytochemicals from TA extracts. Secondly, the mechanisms behind the various medicinal properties of TA extracts are explained. We have also highlighted the role of TA extracts on the green synthesis of metallic nanoparticles, especially silver and gold nanoparticles, with an elucidation on the mechanisms behind the synthesis of nanoparticles. Finally, TA extracts-based polymeric formulations are discussed with limitations and future perspectives. We believe that this review could help researchers understand the importance of a well-known cardioprotective medicinal plant, TA, and its biomedical properties, as well as their role in green nanotechnology and various formulations explored for encapsulating them. This review will help researchers design better and greener nanomedicines as well as better formulations to improve the stability and bioavailability of TA extracts.

Facile Synthesis, Characterization, Anti-Microbial and Anti-Oxidant Properties of Alkylamine Functionalized Dumb-Bell Shaped Copper-Silver Nanostructures

Admirable studies have been established on the utilization of ligand-materials as bimetallic nanoparticles in the field of nanoscience and biotechnology. UV-Vis, XRD, HR-TEM, STEM-HAADF, EDS, FTIR, and DPPH analyses characterized the optical, structural, compositional morphological, and antioxidant properties of synthesized Cu-Ag nanostructures. The spectrum of UV-Vis exhibited absorption bands at 590 and 413 nm, which reflects the surface plasmon resonance of copper-silver nanostructures. Herein, our exploration of alkylamine stabilized copper/silver nanostructures while using hexadecylamine as capping material and their primary biomedical investigation on antimicrobial and antioxidant studies is reported. Cu-Ag bimetallic nanostructures were more effective against gram-negative bacteria E. coli and Klebsiella when compared to gram-positive bacteria. The antioxidant activity of Cu-Ag nanoparticles was comparable with Ascorbic acid.

Antibacterial efficacy of silver nanoparticles synthesized employing Terminalia arjuna bark extract

In the present investigation, we have explored simple, robust, inexpensive, and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Terminalia arjuna bark extract (TA-AgNPs). Various parameters dictating the biosynthesis of TA-AgNPs such as time and temperature of reaction, concentration of AgNO₃, and T. arjuna extract amount were investigated. Characterization of TA-AgNPs was done via UV-vis spectroscopy along with FT-IR, XRD, SEM and dynamic light scattering. The antimicrobial activity of TA-AgNPs was investigated against Escherichia coli. Comparable zone of inhibition was exhibited by TA-AgNPs. This study suggests that TA-AgNPs possesses significant antibacterial properties.

Phytochemically Functionalized Cu and Ag Nanoparticles Embedded in MWCNTs for Enhanced Antimicrobial and Anticancer Properties

Nanomedicine is an emerging field concerned with the use of precision engineered nanomaterials, which leads to the development of novel remedial and diagnostic modalities for human use. In this study, Cu(NO3)2 and AgNO3 precursors were reduced to copper nanoparticles (CuNPs) and silver nanoparticles (AgNPs) using Terminalia arjuna bark extracts under microwave irradiation in the presence of well-dispersed multi-walled carbon nanotubes (MWCNTs) in aqueous medium. The formation of CuNPs or AgNPs and their functionalization with MWCNTs via bioactive molecules of plant extract were evidenced from UV-Vis spectra, XRD, FTIR, FESEM, EDX, and TEM images. The phytochemically functionalized Cu-MWCNTs and Ag-MWCNTs nanomaterials showed enhanced biocide activity, and the inhibitory activity for bacteria was higher than that of fungus. Furthermore, these biohybrid nanomaterials are non-toxic to normal epithelial cells (Vero), whereas they are highly toxic for tested human cancer cells of MDA-MB-231, HeLa, SiHa, and Hep-G2. The cell viability was found to decrease with the increasing dose from 10 to 50 µg mL-1, as well as incubation time from 24 to 72 h. For instance, the cell viability was found to be ~91 % for normal Vero cells and ~76 % for cancer cells for lower dose of 10 µg mL-1.

Phytosynthesis of stable Au, Ag and Au-Ag alloy nanoparticles using J. sambac leaves extract, and their enhanced antimicrobial activity in presence of organic antimicrobials

A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (ϕ20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms.