Phyto-Nanocatalysts: Green Synthesis, Characterization, and Applications

Harnessing plant extracts for eco-friendly synthesis of iron nanoparticle (Fe-NPs): Characterization and their potential applications for ameliorating environmental pollutants

Iron-nanoparticles (Fe-NPs) are increasingly been utilized in environmental applications due to their efficacy and strong catalytic activities. The novelty of nanoparticle science had attracted many researchers and especially for their green synthesis, which can effectively reuse biological resources during the polymerization reactions. Thus, the synthesis of Fe-NPs utilizing plant extracts could be considered as the eco-friendly, simple, rapid, energy-efficient, sustainable, and cost-effective. The green synthesis route can be recognized as a practical, valuable, and economically effective alternative for large-scale production. During the production process, some biomolecules present in the extracts undergo metal salts reduction, which can serve as both a capping and reducing mechanism, enhancing the reactivity and stability of green-synthesized Fe-NPs. The diversity of species provided a wide range of potential sources for green synthesis of Fe-NPs. With improved understanding of the specific biomolecules involved in the bioreduction and stabilization processes, it will become easier to identify and utilize new, potential plant materials for Fe-NPs synthesis. Newly synthesized Fe-NPs require different characterization techniques such as transmission electron microscope, ultraviolet-visible spectrophotometry, and X-ray absorption fine structure, etc, for the determination of size, composition, and structure. This review described and assessed the recent advancements in understanding green-synthesized Fe-NPs derived from plant-based material. Detailed information on various plant materials suitable of yielding valuable biomolecules with potential diverse applications in environmental safety. Additionally, this review examined the characterization techniques employed to analyze Fe-NPs, their stability, accumulation, mobility, and fate in the environment. Holistically, the review assessed the applications of Fe-NPs in remediating wastewaters, organic residues, and inorganic contaminants. The toxicity of Fe-NPs was also addressed; emphasizing the need to refine the synthesis of green Fe-NPs to ensure safety and environmental friendliness. Moving forward, the future challenges and opportunities associated with the green synthesis of Fe-NPs would motivate novel research about nanoparticles in new directions.

Cell based and In vivo systematic evaluation of some Egyptian plant extracts targeting breast cancer

The prevalence of breast cancer as a significant public health concern necessitates continued exploration of natural resources for novel anti-cancer agents is crucial.

MATERIAL AND METHODS

Anticancer activity of plant extracts on monolayer breast cancer cell line (MCF7) with lower levels of toxicity towards normal (RPE1) underwent further assessment using a three-dimensional model (3D). The extract's effects were investigated through multiple assays including apoptosis induction using quantifying cleaved cytokeratin-18 (CK18) and DNA fragmentation. Additionally, the expression of Bcl-2 and Bax was quantitative using real-time PCR. The median lethal dose (LD50) was determined by the acute oral toxicity, while biomarkers associated with tumorigenesis, metastasis, and cell death were quantified by ELISA.

RESULTS

Limoniastrum monopetalum and Bauhinia variegata exhibited the most potent antitumor efficacy among the investigated extracts. They demonstrated potent cytotoxicity against MCF7 with no significant effect on hTERT RPE-1, with an IC50 of 100 μM. The extract demonstrated effectiveness in killing cancer cells within 3D tumor-like structures, induced apoptosis through caspase-3 activation and cleavage of cytokeratin-18, up-regulated the tumor suppressor p53, down-regulated the anti-apoptotic Bcl-2 gene, and caused DNA fragmentation. Acute oral toxicity studies in mice indicated low toxicity, and in a syngeneic mouse tumor model, the extract significantly inhibited tumor growth, suggesting its potential for further development.

CONCLUSION

Limoniastrum monopetalum and Bauhinia variegata exhibited the most potent antitumor efficacy among the investigated extracts.

Very rapid synthesis of highly efficient and biocompatible Ag2Se QD phytocatalysts using ultrasonic irradiation for aqueous/sustainable reduction of toxic nitroarenes to anilines with excellent yield/selectivity at room temperature

There are many problems associated with the synthesis of nanocatalysts and catalytic reduction of nitroarenes - e.g., high temperatures, costs, long reaction/synthesis process times, the toxicity of chemicals/solvents, undesirable byproducts, the toxic/harmful wastes, low efficiency/selectivity, etc. This study represents an attempt to overcome these challenges. To this purpose, biocompatible and highly efficient Ag₂Se quantum dots (QDs) catalysts with antibacterial activity were synthesized in a very rapid (30 sec, rt), simple, inexpensive, sustainable/green, and one-pot strategy in water using ultrasonic irradiation. Characterization of the QDs was performed using different techniques. UV-Vis absorption and fluorescence spectroscopic studies showed an absorption peak at 480-550 nm and a maximum emission peak around 675 nm, which confirmed the successful synthesis of Ag₂Se QDs via the applied biosynthetic method. Subsequently, catalytic reduction of nitroarenes by them was carried out under safe conditions (H₂O, rt, air atmosphere) in ∼ 60 min with excellent yield and selectivity (>99%). Their catalytic activity in the reduction of various toxic nitroarenes to aminoarenes under green conditions was investigated. Thus, a rapid and safe ultrasound-based method was employed to prepare stable and green Ag₂Se QDs phyto-catalysts with unique properties, including exquisite monodispersity in shape (orthorhombic) and size (∼7 nm), air-stability, and good purity and crystallinity. Importantly, instead of various toxic chemicals, the plant extract obtained by rapid ultrasonic method (10 min, rt) was used as natural reducing, capping, and stabilizing agents. Moreover, antibacterial assays results showed that Ag₂Se-QDs catalysts at low concentrations (ppm) have high activity against all tested bacteria, especially E. coli (MIC:31.25 ppm, MBC:125 ppm) which were significantly different from those of Fig extract (MIC = MBC:500 ppm). The data reflect the role of these bio-synthesized Ag₂Se-QDs catalysts in the development of versatile and very safe catalysts with biomedical properties.

Efficacy in degradation of carcinogenic pollutant sulforhodamine B by green synthesized silver nanoparticles

Colloidal Silver nano-particles were grown at room temperature using leaf extract of Ocimum tenuiflorum. The silver nanoparticles suspended in the solution were found to be stable for over a period of 2 months. Structural, optical and photo catalytic behavior of the suspended silver (Ag) nano-particles (NPs) was characterized. From TEM analysis the size of the silver nanoparticles was estimated to be 25–30 nm. Our findings suggest that the ratio between the molarity of AgNO3 and the volume of leaf extract does not have any role in controlling the size of the Ag nano-particles. These green synthesized Ag nano-particles exhibit degradation of the carcinogenic organic pollutant sulforhodamine B in absence of light.

Zinc Oxide Phytonanoparticles' Effects on Yield and Mineral Contents in Fruits of Tomato (Solanum lycopersicum L. cv. Cherry) under Field Conditions

The use of phytonanoparticles in agriculture could decrease the use of fertilizers and therefore decrease soil contamination, due to their size being better assimilated in plants. It is important to mention that the nanofertilizer is slow-releasing and improves plant physiological properties and various nutritional parameters. The influence of soil and foliar applications of phytonanoparticles of ZnO with the Moringa oleifera extract under three concentrations (25, 50, and 100 ppm) was evaluated on the cherry tomato crop (Solanum lycopersicum L.). Synthesis of the phytonanoparticles was analyzed with ultraviolet-visible spectroscopy (UV-Vis) and infrared transmission spectroscopy with Fourier transform (FT-IR), as well as the analysis with the dynamic light scattering (DLS) technique. The morphometric parameters were evaluated before and after the application of the nanoparticles. The minerals' content of fruits was done 95 days after planting. Results showed that soil application was better at a concentration of 25 ppm of phytonanoparticles since it allowed the greatest number of flowers and fruits on the plant; however, it was demonstrated that when performing a foliar application, the fruit showed the highest concentrations for the elements Mg, Ca, and Na at concentrations of 511, 4589, and 223 mg kg⁻¹, respectively.

Assembly of fluorinated chromanones via enantioselective tandem reaction

The enantioselective synthesis of fluorinated tricyclic chromanones with multiple vicinal stereogenic centers has been realized for the first time, through the tandem reaction between 2-fluorinated 1-(2-hydroxyaryl)-1,3-diketones and α,β-unsaturated aldehydes. In the presence of chiral amine, the organo-tandem reaction including catalytic Michael addition/cycloketalization/hemiacetalization and acylation sequence provided a wide range of fluorinated tricyclic chromanones with excellent outcomes (>30 examples, up to >99% ee and >19 : 1 d.r.). A plausible catalytic cycle and transition state are also provided for this tandem reaction to rationalize the observed sense of asymmetric induction.

One-pot green synthesis of gold and silver nanoparticles using Rosa canina L. extract

This study reports a green, simple, and fast method for the synthesis of gold and silver nanoparticles using natural antioxidant compounds. The aqueous extract from dried rosehips (pseudofruit of Rosa canina L.) was used as a reducing and capping agent of HAuCl4 and AgNO3 during the noble metal colloid synthesis at room temperature and no other chemical reagent was used. The high antioxidant activity of the plant extract was proven by 2,2-diphenyl-1-picrylhydrazyl assay by a spectrophotometric method. The formation of stable gold and silver nanoparticles was observed by UV-visible spectroscopy and the evolution of their characteristic surface plasmon resonance band was followed over several days. Transmission electron microscopy confirmed the formation of quasi-spherical nanoparticles with mean diameters 26 and 34 nm, for gold and silver nanoparticles, respectively; XRD revealed an FCC crystalline structure for both gold and silver NPs. The effects of concentrations of noble metal precursor and plant extract solution on the formation, stabilization and size of nanoparticles are discussed, as well as some applications of these colloids.

In Vitro and In Vivo Evaluation of Silver Nanoparticles Phytosynthesized Using Raphanus sativus L. Waste Extracts

The aim of the current paper is the development of phytosynthesized silver nanoparticles mediated by Raphanus sativus L. extracts obtained through two extraction methods (temperature and microwave) and to test their potential application for controlling apple crops pathogens. The phytosynthesized materials were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. All the materials were evaluated in terms of antioxidant and in vitro antimicrobial activity (against bacteria, molds, and yeast: Escherichia coli ATCC 8738, Staphylococcus aureus ATTC 25923, Pseudomonas aeruginosa ATCC 9027, Salmonella typhimurium ATCC 14028, Candida albicans ATCC 10231, Venturia inaequalis, Podosphaera leucotricha, Fusarium oxysporum ATCC 48112, Penicillium hirsutum ATCC 52323, and Aspergillus niger ATCC 15475). Considering the results obtained in the in vitro assays, formulations based on nanoparticles phytosynthesized using Raphanus sativus L. waste extracts (RS1N) were evaluated as potential antifungal agents for horticultural crops protection, against Venturia inaequalis and Podosphaera leucotricha through in vivo assays. For the DPPH assay, the inhibition (%) varied between 37.06% (for RS1N at 0.8 mg/mL concentration) and 83.72% (for RS1N at 7.2 mg/mL concentration) compared to 19.97% (for RS2N at 0.8 mg/mL) and only 28.91% (for RS2N at 7.2 mg/mL). Similar results were obtained for RS3N (85.42% inhibition at 7.2 mg/mL) compared with RS4N (21.76% inhibition at 7.2 mg/mL). Regarding the ABTS assay, the highest scavenger activity values were recorded for samples RS1N (91.43% at 1.6 mg/mL) and RS3N (96.62% at 1.6 mg/mL).

Plantago media L.-Explored and Potential Applications of an Underutilized Plant

The search of valuable natural compounds should be directed towards alternative vegetal resources, and to the re-discovery of underutilized plants. Belonging to the Plantaginaceae family, the hoary plantain (Plantago media L.) represents one of the lesser studied species from the Plantago genus. The literature study revealed the under-utilization of the hoary plantain, a surprising aspect, considering its widespread. If the composition of Plantago media L. is rather well established, its applications are not nearly studied as for other Plantago species. The goal of the present paper is to summarize the findings regarding the applications of P. media, and, having as starting point the applications of related species, to propose new emerging areas of research, such as the biomedical applications validation through in vivo assays, and the evaluation of its potential towards industrial applications (i.e., development of food or personal care products), pisciculture or zootechny, phytoremediation and other environmental protection applications, or in the nanotechnology area (materials phytosynthesis). The present work constitutes not only a brief presentation of this plant's present and potential applications, but also an invitation to research groups world-wide to explore the available vegetal resources.

Recent developments in the synthesis of polysubstituted pyridines via multicomponent reactions using nanocatalysts

This review describes the evolution and application of active metal-based and heterometallic NPs as efficient heterogeneous catalysts for the synthesis of pyridine derivatives by multicomponent reactions in the last decade (2010–2020).

Green Synthesis of an Activated Carbon-Supported Ag and ZnO Nanocomposite for Photocatalytic Degradation and Its Antibacterial Activities

In this study Ag nanoparticles (AgNPs), ZnO nanoparticles (ZnONPs), and Ag/ZnO nanocomposites were greenly synthesized and loaded on activated carbon via three different routes: simple impregnation, successive precipitation, and co-precipitation. Neem leaf extract was used as a reducing and stabilizing agent. The morphological and structural properties of the synthesized nanocomposites have been examined using different analytical techniques such as XRD, SEM, FTIR, and UV. The antibacterial and catalytic activity of the synthesized nanocomposites were examined and compared. The results showed that AgNPs loaded on activated carbon (Ag/AC) has the best catalytic activity compared to the other nanocomposites, which is attributed to the good dispersal of AgNPs on the surface of activated carbon. Furthermore, AgNPs showed the best antibacterial effect on eight out of 16 tested pathogens. Results also showed that the order of precipitation is an important factor, as both antibacterial activities and photodegradation activities were higher for ZnO/Ag/AC than Ag/ZnO/AC. Furthermore, the co-precipitation method was shown to be better than the successive precipitation method for 4-nitrophenol photodegradation and 14 out of the 16 antibacterial tests performed.

Phytosynthesized Metallic Nanoparticles-between Nanomedicine and Toxicology. A Brief Review of 2019's Findings

Phytosynthesized nanoparticles represent a continuously increasing field of research, with numerous studies published each year. However, with the emerging interest in this area, the quality of the published works is also continuously increasing, switching from routine antioxidant or antimicrobial studies on trivial microbial lines to antibiotic-resistant strains or antitumoral studies. However, this increasing interest has not been not reflected in the studies regarding the toxicological effects of nanoparticles (NPs); this should be a subject of greatest interest, as the increasing administration of NPs in general (and phytosynthesized NPs in particular) could lead to their accumulation in the environment (soil, water and living organisms). The present review aims to present the most recent findings in the application of phytosynthesized NPs as antimicrobial and antitumoral agents, as well as the results regarding their toxicological potential.

Fragaria Genus: Chemical Composition and Biological Activities

The strawberries represent in our days one of the main fresh fruits consumed globally, inevitably leading to large amounts of by-products and wastes. Usually appreciated because of their specific flavor, the strawberries also possess biological properties, including antioxidant, antimicrobial, or anti-inflammatory effects. In spite of the wide spread of the Fragaria genus, few species represent the subject of the last decade scientific research. The main components identified in the Fragaria species are presented, as well as several biological properties, as emerging from the scientific papers published in the last decade.

A Short Overview of Recent Developments on Antimicrobial Coatings Based on Phytosynthesized Metal Nanoparticles

The phytosynthesis of metallic nanoparticles represents an exciting new area of research, with promising perspectives, gaining in the last decades an increasing importance. Nanotechnology represents an important tool and an efficient option for obtaining particles with controlled morphology and shapes, phytosynthesized nanoparticles (NPs) being a good alternative to remove hazardous reagents. Due to the practical applications of the phytosynthesized nanoparticles, which are mainly associated with their antimicrobial potential, the abundance of scientific literature in this domain is given by researches in the phytosynthesis of metallic nanoparticles (3654 articles) and the evaluation of their antimicrobial properties (2338 papers). The application of phytosynthesized nanoparticles as antimicrobial coatings represented the subject of only 446 works, which lead us to the subject of this review paper. Application of antimicrobial coatings containing phytosynthesized nanoparticles for the development of antimicrobial textiles, other biomedical applications, protection of food (including fruits and vegetables), as well as for other types of applications based on their antimicrobial potential are covered by the present review.

Recovery of Natural Antioxidants from Agro-Industrial Side Streams through Advanced Extraction Techniques

Large amounts of agro-industrial waste are being generated each year, leading to pollution and economic loss. At the same time, these side streams are rich source of active compounds including antioxidants. Recovered compounds can be re-utilized as food additives, functional foods, nutra-/pharmaceuticals, cosmeceuticals, beauty products, and bio-packaging. Advanced extraction techniques are promising tools to recover target compounds such as antioxidants from agro-industrial side streams. Due to the disadvantages of classical extraction techniques (such as large amounts of solvents, increased time of extraction, large amounts of remaining waste after the extraction procedure, etc.), and advanced techniques emerged, in order to obtain more efficient and sustainable processes. In this review paper aspects regarding different modern extraction techniques related to recovery of antioxidant compounds from wastes generated in different industries and their applications are briefly discussed.