Green Synthesis and Antimicrobial Potential of Silver Nanoparticles with Boerhavia procumbens Extract

Green synthesis of silver nanoparticles using guava leaves: an effective strategy to control chilli fruit rot disease

BACKGROUND

Anthracnose, caused by Colletotrichum capsici, is a significant fungal disease affecting chilli crops, leading to yield losses of 10-25%. Traditional control methods, primarily chemical fungicides, not only pose risks to the environment and soil health but also threaten public safety. In contrast, nanotechnology presents a promising eco-friendly alternative, leveraging the unique properties of nanoparticles, such as their small size and high surface-to-volume ratio, to effectively manage fungal infections with minimal environmental impact.

RESULTS

This study investigates the synthesis, characterization, and antifungal activity of silver nanoparticles (Ag-NPs) synthesized from guava leaf extract against chilli fruit rot. UV-Vis spectroscopy confirmed the synthesis of Ag-NPs with a peak absorption at 431 nm. X-ray diffraction (XRD) analysis revealed a crystalline structure with an average particle size of 42.5 nm, while scanning electron microscopy (SEM) showed spherical nanoparticles with sizes ranging from 30.5 nm to 50.3 nm across different samples. Fourier transform infrared spectroscopy (FTIR) identified functional groups involved in silver ion reduction. Zeta size analysis confirmed particle sizes of 500.1 nm, 1.0 nm, 62.4 nm, 262.8 nm, and 178.8 nm for samples S1 through S5, respectively. In antifungal assays, S1 at 50 ppm exhibited the highest mycelial growth inhibition (47.9%), with significant protective (87%) and curative (93%) effects. Additionally, in in-vitro leaflet assays, S1 demonstrated 86% inhibition of C. capsici at 50 ppm, highlighting its potential as an effective agent for managing chilli fruit rot.

CONCLUSIONS

This study presents a rapid, eco-friendly method for synthesizing Ag-NPs using guava leaf extract, showing their potential in managing chilli fruit rot caused by C. capsici. The results highlight their effectiveness in both protective and curative applications, offering a sustainable alternative to chemical fungicides. Future research should focus on scaling up the synthesis process for industrial applications, exploring the long-term environmental impact, and assessing the broader applicability of Ag-NPs in managing other phytopathogenic diseases across various crops. Silver nanoparticles (Ag-NPs) synthesized from guava leaf extract effectively inhibit Colletotrichum capsici, with 86% antifungal activity at 50 ppm. This study highlights an eco-friendly, rapid synthesis method for Ag-NPs as a promising alternative to chemical fungicides in managing chilli fruit rot disease.

CLINICAL TRIAL NUMBER

Not applicable.

Cytotoxic Effects of ZnO and Ag Nanoparticles Synthesized in Microalgae Extracts on PC12 Cells

The green synthesis of silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs), as well as Ag/Ag2O/ZnO nanocomposites (NCs), using polar and apolar extracts of Chlorella vulgaris, offers a sustainable method for producing nanomaterials with tunable properties. The impact of the synthesis environment and the nanomaterials' characteristics on cytotoxicity was evaluated by examining reactive species production and their effects on mitochondrial bioenergetic functions. Cytotoxicity assays on PC12 cells, a cell line originated from a rat pheochromocytoma, an adrenal medulla tumor, demonstrated that Ag/Ag2O NPs synthesized with apolar (Ag/Ag2O NPs A) and polar (Ag/Ag2O NPs P) extracts exhibited significant cytotoxic effects, primarily driven by Ag+ ion release and the disruption of mitochondrial function. However, it is more likely the organic content, rather than size, influenced anticancer activity, as commercial Ag NPs, despite smaller crystallite sizes, exhibit less effective activity. ZnO NPs P showed increased reactive oxygen species (ROS) generation, correlated with higher cytotoxicity, while ZnO NPs A produced lower ROS levels, resulting in diminished cytotoxic effects. A comparative analysis revealed significant differences in LD50 values and toxicity profiles. Differentiated PC12 cells showed higher resistance to ZnO, while AgNPs and Ag/Ag2O-based materials had similar effects on both cell types. This study emphasizes the crucial role of the synthesis environment and bioactive compounds from C. vulgaris in modulating nanoparticle surface chemistry, ROS generation, and cytotoxicity. The results provide valuable insights for designing safer and more effective nanomaterials for biomedical applications, especially for targeting tumor-like cells, by exploring the relationships between nanoparticle size, polarity, capping agents, and nanocomposite structures.

The Green Synthesis of Silver Nanoparticles from Avena fatua Extract: Antifungal Activity against Fusarium oxysporum f.sp. lycopersici

Using plant extracts as eco-friendly reducing and stabilizing agents for the synthesis of nanoparticles has gained significant attention in recent years. The current study explores the green synthesis of silver nanoparticles (AgNPs) using the Avena fatua extract and evaluates their antifungal activity against Fusarium oxysporum f.sp. lycopersici (Fol), a fungal plant pathogen. A green and sustainable approach was adopted to synthesize silver nanoparticles before these nanoparticles were employed for anti-fungal activity. The primary indication that AgNPs had formed was performed using UV-vis spectroscopy, where a strong peak at 425 nm indicated the effective formation of these nanoparticles. The indication of important functional groups acting as reducing and stabilizing agents was conducted using the FTIR study. Additionally, morphological studies were executed via SEM and AFM, which assisted with more effectively analyzing AgNPs. Crystalline behavior and size were estimated using powder XRD, and it was found that AgNPs were highly crystalline, and their size ranged from 5 to 25 nm. Synthesized AgNPs exhibited significant antifungal activity against Fol at a concentration of 40 ppm. Furthermore, the inhibitory index confirmed a positive correlation between increasing AgNPs concentration and exposure duration. This study suggests that the combined phytochemical mycotoxic effect of the plant extract and the smaller size of synthesized AgNPs were responsible for the highest penetrating power to inhibit Fol growth. Moreover, this study highlights the potential of using plant extracts as reducing and capping agents for the green synthesis of AgNPs with antifungal properties. The study concludes that A. fatua extract can synthesize antifungal AgNPs as a sustainable approach with robust antifungal efficacy against Fol, underscoring their promising potential for integration into plant protection strategies.

Biosynthesized silver nanoparticles using Polygonatum geminiflorum efficiently control fusarium wilt disease of tomato

Nanomaterials are gaining tremendous potential as emerging antimicrobials in the quest to find resistance-free alternatives of chemical pesticides. In this study, stable silver nanoparticles were synthesized using the aqueous extract of medicinal plant species Polygonatum geminiflorum , and their morphological features were evaluated by transmission electron microscopy, X-ray diffraction spectroscopy and energy dispersive X-ray analysis. In vitro Antifungal activity of the synthesized silver nanoparticles (AgNPs) and P. geminiflorum extract (PE) either alone or in combination (PE-AgNPs) against Fusarium oxysporum was evaluated using disc-diffusion and well-diffusion methods. In planta assay of the same treatments against Fusarium wilt diseases of tomato was evaluated by foliar spray method. Moreover, plant extract was evaluated for the quantitative investigation of antioxidant activity, phenolics and flavonoids by spectroscopic and HPLC techniques. Phytochemical analysis indicated the presence of total phenolic and flavonoid contents as 48.32 mg ± 1.54 mg GAE/g and 57.08 mg ± 1.36 mg QE/g, respectively. The DPPH radical scavenging of leaf extract was found to be 88.23% ± 0.87%. Besides, the HPLC phenolic profile showed the presence of 15 bioactive phenolic compounds. Characterization of nanoparticles revealed the size ranging from 8 nm to 34 nm with average crystallite size of 27 nm. The FTIR analysis revealed important functional groups that were responsible for the reduction and stabilization of AgNPs. In the in vitro assays, 100 μg/ml of AgNPs and AgNPs-PE strongly inhibited Fusarium oxysporum. The same treatments tested against Fusarium sprayed on tomato plants in controlled environment exhibited nearly 100% plant survival with no observable phytotoxicity. These finding provide a simple baseline to control Fusarium wilt using silver nano bio-control agents without affecting the crop health.

Evaluation of Modified Date Palm (Phoenix dactylifera L.) Mucilage as a Potential Pharmaceutical Excipient

Investigation on natural sources from plants, animals, and microorganisms that produce gums and mucilages goes on increasing day by day to check their pharmaceutical applications. Different mucilages have been studied for their pharmaceutical effects but the use of date palm (Phoenix dactylifera L.) mucilage as a pharmaceutical excipient is still under the cover. The aim of this study was therefore to evaluate and compare the flow property and binding ability of crude, purified, modified (hydrolyzed and grafted), green synthesized nanoparticles (Zinc oxide (ZnO), cuperic oxide (CuO), silver (Ag), and gold (Au)) of date palm mucilage with hydroxy propyl methyl cellulose (HPMC) and commercially available paracetamol tablets. Previously purified mucilage (with 58.4% yield) was subjected to modification (i.e., acidic, basic, and enzymatic), grafting (polyacrylamide), and green synthesis of nanoparticles. Flow properties of powdered (granular) crude, purified, modified, and nanoparticles were studied and compared with flow properties of HPMC and paracetamol tablet granules. Tablets were made using granules of all types of date palm mucilage (discussed above), HPMC, and granules of paracetamol tablets to study and compare weight uniformity, hardness, friability, dissolution rate, and disintegration time. When 100 mg/kg of mucilage sample was given to mice no oral toxicity was found. The results obtained during this study were within the acceptable ranges given in pharmacopeias. The pseudoplastic flow behavior, hygroscopic nature, increased solubility, and swelling index across the increase in temperature, hardness of the tablets, friability, and drug release behavior were found better than HPMC and the binders used in commercially available paracetamol, hence making the date palm mucilage (crude, purified, and modified) an excellent excipient to be used in pharmaceutical dosage forms.

Fagonia cretica-Mediated Synthesis of Manganese Oxide (MnO2) Nanomaterials Their Characterization and Evaluation of Their Bio-Catalytic and Enzyme Inhibition Potential for Maintaining Flavor and Texture in Apples

The apple is the most widely used fruit globally. Apples are more prone to fungal spoilage, which leads to browning and subsequent changes in their flavor and texture. Browning is also caused by the tyrosinase enzyme. By inhibiting tyrosinase initiation and fungal spoilage in fruits, the natural flavor and texture of fruits can be maintained. Biogenic NPs can act as antioxidants to inhibit tyrosinase and due to oxidative stress, it also catalyzes the deformation of fungal hyphae and spores. Nanotechnology is a research hotspot that has gained considerable interest due to its potential inferences in biosciences and food preservation technology. The present study aims to use biomass from the Fagonia cretica to create bio-inspired manganese oxide MnO2 NPs and to evaluate its bio-catalytic potential for antifungal anti-browning through the inhibition of tyrosinase and its antioxidant potential for preserving apple flavor and texture. The green synthesized nanoparticles were extensively analyzed using UV spectroscopy, XRD, SEM, EDX, and FTIR techniques. Moreover, the synthesized manganese oxide nanoparticles (MnO2 NPs) were evaluated for their bio-catalytic potential as anti-fungal and anti-spoiling agents. The values of antifungal activity among all the samples were 14.2 ± 86 mm, 8.9 ± 6.0 mm, 17.7 ± 1.26, and 20.7 ± 4.38 mm for Penicillium expansum, Monilinia fructigena, Penicillium chrysogenum, and Aspergillus oryzae at 200 µg/well, respectively. Moreover, the biogenic NPs were evaluated for their anti-browning potential through the inhibition of tyrosinase. MnO2 NPs have been shown to have considerable inhibitory effects on tyrosinase up to 64.8 ± 0.16 at 200 µg/mL and (27.2 ± 0.58) at 25 µg/mL. Biogenic MnO2 NPs can also act as antioxidants to inhibit tyrosinase and fungal growth by the formation of free radicals that damage the fungal hyphae and, as a result, slow down browning. The maximum DPPH free radical scavenging activity was 74.5 ± 0.39% at 200 µg/mL, and the minimum was 12.4 ± 0.27 at 25 µg/mL. The biogenic MnO2 NPs are biocompatible and play a potent role in maintaining the flavor and texture of apples.

Biosynthesis of Bimetallic Cu-Ag Nanocomposites and Evaluation of their Electrocatalytic, Antibacterial and Anti-Cancerous Activity

Bimetallic nanocomposites have evolved into a significant smart material in the recent past. Owing to the growing interest, we herein report the biosynthesis of bimetallic silver doped copper (Cu-Ag) nanocomposites using green methods by utilizing aqueous extract of Carica papaya leaves. The optical property and the surface morphology of the nanoparticles were determined by using various analytical techniques like Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX) and Transmission Electron Microscopy (TEM). The redox behaviour of the bimetallic nanocomposites was studied using Cyclic Voltammetry (CV) with platinum electrode in 0.1M KCl solution at different scan rates and concentrations. The FTIR revealed the presence of active components of the leaf extract which played the roles of surfactants, stabilizing, capping, and reducing agents. Similarly, SEM with EDAX exhibited the presence of spherically agglomerated Cu-Ag nanocomposites and TEM images revealed a particle size of 20 nm. The gradual increase in peak current was observed in CV with increase in the scan rates and concentrations apparently. The bimetallic nanocomposites showed potential anti-bacterial, anti-cancerous activity and the reports are provided in detail.

Recent Advances in Green Synthesis of Ag NPs for Extenuating Antimicrobial Resistance

Combating antimicrobial resistance (AMR) is an on-going global grand challenge, as recognized by several UN Sustainable Development Goals. Silver nanoparticles (Ag NPs) are well-known for their efficacy against antimicrobial resistance, and a plethora of green synthesis methodologies now exist in the literature. Herein, this review evaluates recent advances in biological approaches for Ag NPs, and their antimicrobial potential of Ag NPs with mechanisms of action are explored deeply. Moreover, short and long-term potential toxic effects of Ag NPs on animals, the environment, and human health are briefly discussed. Finally, we also provide a summary of the current state of the research and future challenges on a biologically mediated Ag-nanostructures-based effective platform for alleviating AMR.

Seaweed bioactive compounds: Promising and safe inputs for the green synthesis of metal nanoparticles in the food industry

Scientific research on developing and characterizing eco-friendly metal nanoparticles (NPs) is an active area experiencing currently a systematic and continuous growth. A variety of physical, chemical and more recently biological methods can be used for the synthesis of metal nanoparticles. Among them, reports supporting the potential use of algae in the NPs green synthesis, contribute with only a minor proportion, although seaweed was demonstrated to perform as a successful reducing and stabilizing agent. Thus, the first part of the present review depicts the up-to-date information on the use of algae extracts for the synthesis of metal nanoparticles, including a deep discussion of the certain advantages as well as some limitations of this synthesis route. In the second part, the available characterization techniques to unravel their inherent properties such as specific size, shape, composition, morphology and dispersibility are comprehensively described, to finally focus on the factors affecting their applications, bioactivity, potential toxic impact on living organisms and incorporation into food matrices or food packaging, as well as future prospects. The present article identifies the key knowledge gap in a systematic way highlighting the critical next steps in the green synthesis of metal NPs mediated by algae.

Green Synthesis and Antimicrobial Potential of Silver/Gold Nanoparticles Functionalized with Debregeasia salicifolia D. Don

The aim of the current study was to detect various secondary metabolites in the extract of Debregeasia salicifolia, and to synthesize stable silver/gold nanoparticles (Ag/AuNPs) from D. salicifolia methanol crude extract. The antioxidant, antibacterial, and antifungal activities of the methanol crude extract, various isolated fractions, and the synthesized nanoparticles were evaluated. Phytochemical analyses of the methanol extract/fractions indicated the presence of tannins, saponins, flavonoids, steroids, terpenoids, coumarins, emodins, and soluble starch. Gold and silver nanoparticles have been subsequently synthesized from the methanol crude extract by green synthesis, and characterized by UV and IR spectroscopic techniques. Size of the particles was determined with the aid of an atomic force microscope (AFM). The results revealed that the size of AuNPs was 5-100 nm, and that of AgNPs was in the range 5-100 nm. Bioactivity screening revealed that chloroform and n-hexane fractions exhibited significant 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical scavenging potential against quercetin. Additionally, the extract/fractions and AuNPs were also subjected to antimicrobial activity screening against a number of strains of microbes. Among extracts, n-hexane fraction showed good antifungal activity as compared to other fractions, whereas in the case of anti-bacterial activity, extract and fractions were active against Gram positive and Gram negative bacterial strain. AuNPs were exhibited moderate activity against all tested bacterial strains.

Synthesis, Characterization, and Antimicrobial Properties of Sparfloxacin-Mediated Noble Metal Nanoparticles

The aim of the current research finding was to synthesize, characterize and antibacterial evaluation of sparfloxacin-mediated noble metal nanoparticles. Noble metal [silver (Ag), and gold (Au)] nanoparticles (NPs), mediated with fluoroquinolone, an anti-bacterial drug [Sparfloxacin, (Sp)], was synthesized by a facile and convenient procedure. Formulated Ag-Sp NPs, and Au-Sp NPs exhibited stability against variation in pH, NaCl solution, temperature, and time. The structural topographies of Ag-Sp, and Au-Sp NPs were determined by fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM) atomic force microscopy (AFM), and energy dispersive X-ray (EDX). UV-Vis revealed the formulation of NPs by showing typical surface Plasmon absorption maxima at 410 nm for Ag-Sp NPs and 555 nm for Au-Sp NPs. The AFM and SEM analysis ascertained stable mono dispersed Ag-Sp NPs and Au-Sp NPs in the size range of 40-50 nm, and 70-80 nm, respectively. Ag-Sp, and Au-Sp NPs exhibited antibacterial traits against Bacillus subtilis, Staphylococcus aureus, and Klebsiella pneumonia, showing a zone of inhibition (ZOI) ranging from 20±0.98 mm to 24±0.94 mm (Ag-Sp NPs), and 22±0.79 mm to 26±0.92 mm (Au-Sp NPs) at dose of 3 mg/mL.