Brown Color Formation Research Articles

Silver nanoparticles mediated apoptosis and cell cycle arrest in lung cancer A549.

The present study was aimed to synthesize the silver nanoparticles from Alangium salvifolium Wang. and evaluating its biomedical applications. The leaves of A. salvifolium collected and subjected for the standard procedure of Soxhlet extraction using distilled water as a solvent. With the help of an aqueous extract AgNPs were synthesized from silver nitrate using phyto-reduction method. Further, synthesized AgNPs were characterized using several analytical techniques such as UV, FTIR, SEM-EDX, XRD, particles size and zeta potential. Synthesized AgNPs were tested for antibacterial, antioxidant, anticancer for lung cancer cell line and flowcytometry-based pathway studies. The visual observation confirmed the formation of AgNPs from the aqueous extract by changing yellow to brown colour formation. Further, characterization techniques also confirmed the formation of AgNPs. Antibacterial activity results showed that the tested AgNPs were potent against bacterial pathogens with a higher zone of inhibition. Further, the antioxidant and anticancer activity of AgNPs revealed that the AgNPs have exhibited significant results with a good percentage of inhibition. Further, the flow cytometry studies confirmed that the AgNPs inducing apoptosis and cell cycle arrest in lung cancer. The phytochemicals of A. salvifolium plant have successfully synthesized AgNPs. In the case of performed biological activity, the synthesized silver nanoparticles exhibited potent activity. In future these AgNPs can be taken for molecular and in vivo studies to identify their efficacy using in vivo and molecular models.

Dye stability of black cherry plum anthocyanins in the interaction with co-pigments and sucrose sweetener.

In this research, the co-pigmentation reactions between black cherry plum (Prunus cerasifera Ehrh. cv. Pissardii Nigra) anthocyanins and caffeic, gallic, 4-hydroxybenzoic, malic, and tannic acids with different concentrations (0, 120, 240, 480, and 960 mg L-1) at various temperatures (20, 40, 60, 80, and 100°C) were investigated at pH 3.5. The strongest immediate co-pigmentations resulted at 960 mg L-1, being significantly highest using tannic acid at all temperatures. In addition, the anthocyanin stability and the brown polymeric color formation were investigated in the presence of different concentrations of sucrose sweetener (0, 30, and 60%) and different pHs (2 and 3) in the range of 0-60 h. Also, the amount of furfural was measured in the presence of 0% and 30% sucrose concentrations at pH 2 after 20 h at 90°C by HPLC (high-performance liquid chromatography), and the most polymeric color formation was observed in the concentration of 60% sucrose at pH 2 after 60 h.

Antibacterial Effects of Phytofabricated Silver Nanoparticles Against Some Selected Bacteria.

The increase in multidrug resistance microorganisms has initiated the creation of other means of combating the damages caused by these microbes by scientists. This has led to the creation of more affordable, environmental friendly and cost effective antimicrobial agents in which formation of nanoparticle using plant leave extracts fits in rather than chemically synthesized antibiotics which have previously been in used. In this study, the efficacy of phyto-fabricated silver nanoparticle and its antibacterial effect against some bacteria which were collected from a research laboratory located in Awka, Anambra state were identified. To generate the aqueous extract of silver nanoparticle, the various plant leaves were dried for one week at a room temperature of 40oC. The dried leaf were pulverized, dissolved in 100mL deionized water and heated to a boiling temperature for 5 minutes until a nanoparticle is formed through the formation of dark brown colour and a double fitration is carried out using whatman no 1 filter paper. The synthesised silver nanoparticle was centrifuged, dried and used for antibacterial analysis. The antibacterial analysis was carried out using agar well diffusion method. The results from the antibacterial screening revealed that the tested organisms were susceptible to silver nanoparticles with Proteus mirabilis showing the highest zone of inhibition for cashew fabricated silver nanoparticle at 28.00±0.45 and concentration of 3.13mg/ml, while the lowest zone of inhibition using Carica papaya fabricated silver nanoparticle was observed with Pseudomonas aeruginosa at 4.00±0.36 and concentration of 6.25mg/ml. The negative control (DMSO) used did not produce any zone of inhibition on the tested organisms. Statistically, there was significant (P<0.005) inhibition of bacteria pathogenic strains among the means of A. muricata, C. papaya and A. occidentalis fabricated silver nanoparticle and ciprofloxacin standard antibiotics. The high antibacterial inhibition of the tested bacterial strains by A. muricata, C. papaya and A. occidentalis fabricated silver nanoparticle at minimal inhibitory concentration of 6.25mg/mL could be exploited as biostatic and biocidal agent. This shows that nanoparticle synthesised using biologically materials like plant part, are highly potent, cheaper to synthesized and as well, less toxic.

Antibacterial Effects of Phytofabricated Silver Nanoparticles Against Some Selected Bacteria.

The increase in multidrug resistance microorganisms has initiated the creation of other means of combating the damages caused by these microbes by scientists. This has led to the creation of more affordable, environmental friendly and cost effective antimicrobial agents in which formation of nanoparticle using plant leave extracts fits in rather than chemically synthesized antibiotics which have previously been in used. In this study, the efficacy of phyto-fabricated silver nanoparticle and its antibacterial effect against some bacteria which were collected from a research laboratory located in Awka, Anambra state were identified. To generate the aqueous extract of silver nanoparticle, the various plant leaves were dried for one week at a room temperature of 40oC. The dried leaf were pulverized, dissolved in 100mL deionized water and heated to a boiling temperature for 5 minutes until a nanoparticle is formed through the formation of dark brown colour and a double fitration is carried out using whatman no 1 filter paper. The synthesised silver nanoparticle was centrifuged, dried and used for antibacterial analysis. The antibacterial analysis was carried out using agar well diffusion method. The results from the antibacterial screening revealed that the tested organisms were susceptible to silver nanoparticles with Proteus mirabilis showing the highest zone of inhibition for cashew fabricated silver nanoparticle at 28.00±0.45 and concentration of 3.13mg/ml, while the lowest zone of inhibition using Carica papaya fabricated silver nanoparticle was observed with Pseudomonas aeruginosa at 4.00±0.36 and concentration of 6.25mg/ml. The negative control (DMSO) used did not produce any zone of inhibition on the tested organisms. Statistically, there was significant (P<0.005) inhibition of bacteria pathogenic strains among the means of A. muricata, C. papaya and A. occidentalis fabricated silver nanoparticle and ciprofloxacin standard antibiotics. The high antibacterial inhibition of the tested bacterial strains by A. muricata, C. papaya and A. occidentalis fabricated silver nanoparticle at minimal inhibitory concentration of 6.25mg/mL could be exploited as biostatic and biocidal agent. This shows that nanoparticle synthesised using biologically materials like plant part, are highly potent, cheaper to synthesized and as well, less toxic.

An in-depth analysis of initial processing steps in the extraction of proteins from tomato (Solanum lycopersicum) leaves

Tomato leaves, the by-products from tomato production, are a promising source of proteins. An important challenge to extract proteins is that leaves are perishable materials. Here we investigated different post-harvest processing routes of tomato leaves (fresh processing, three-day storage, freezing, freeze drying and oven drying) to understand their effects on protein extractability from leaves. Proteins were extracted at floating pH and alkaline condition (pH 10). Obtained protein fractions were characterized according to protein solubility, protein profile, molecular weight distribution, secondary structure and color. Results showed that tomato leaves should be processed fresh for protein extraction. Alternatively, leaves can be stored for three-day at room temperature. Extraction at pH 10 did not result in enhanced protein extraction but led to dark brown color formation. Extensive protein degradation was induced during oven drying, providing a new processing route when degraded products such as peptides and free amino acids are the target products. Industrial relevanceTo support the transition of human diet from animal-based to plant-based, it is important to find new plant protein sources. Tomato leaves, the by-products of tomato fruit production, are widely available and are unexplored source of proteins. An additional challenge of using leaves as a protein source lies in the perishable nature of tomato leaves. The presented study discussed the post-harvest processing options to extract proteins from tomato leaves. Our findings provided insights on how to upscale protein extraction from tomato leaves in the future.

Facile Synthesis and Characterization of Chitosan Functionalized Silver Nanoparticles for Antibacterial and Anti-Lung Cancer Applications.

In the treatment of bacterial contamination, the problem of multi-drug resistance is becoming an increasingly pressing concern. Nanotechnology advancements enable the preparation of metal nanoparticles that can be assembled into complex systems to control bacterial and tumor cell growth. The current work investigates the green production of chitosan functionalized silver nanoparticles (CS/Ag NPs) using Sida acuta and their inhibition efficacy against bacterial pathogens and lung cancer cells (A549). Initially, a brown color formation confirmed the synthesis, and the chemical nature of the synthesized NPs were examined by UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). FTIR demonstrated the occurrence of CS and S. acuta functional groups in the synthesized CS/Ag NPs. The electron microscopy study exhibited CS/Ag NPs with a spherical morphology and size ranges of 6-45 nm, while XRD analysis demonstrated the crystallinity of Ag NPs. Further, the bacterial inhibition property of CS/Ag NPs was examined against K. pneumoniae and S. aureus, which showed clear inhibition zones at different concentrations. In addition, the antibacterial properties were further confirmed by a fluorescent AO/EtBr staining technique. Furthermore, prepared CS/Ag NPs exhibited a potential anti-cancer character against a human lung cancer cell line (A549). In conclusion, our findings revealed that the produced CS/Ag NPs could be used as an excellent inhibitory material in industrial and clinical sectors.

Metallo-Surfactant assisted silver nanoparticles: A new approach for the colorimetric detection of amino acids

In this study, we report a new class of metallo-surfactant assisted silver nanoparticle produced by reduction process via AgNO3 solution and extract of Turnera Subulata (TS) in aqueous which act as reducing and metallo-surfactant [Co(ip)2(C12H25NH2)2](ClO4)3 (ip = imidazo[4,5-f][1,10]phenanthroline) act as stabilizing agent. In this study the silver nanoparticles produced using Turnera Subulata extract has showed yellowish brown color formation and an absorption peak at 421 nm signaling the biosynthesis of silver nanoparticles. The presence of functional groups in the plant extracts were identified by FTIR analysis. In addition, the effects of ratio, changing the concentration of the metallo surfactant, TS plant leave extract, metal precursors, and pH of the medium have been investigated on the scale of the Ag nanoparticles. Spherical shaped, crystalline in nature and ∼50 nm sized particles were recorded using TEM and DLS analysis. Furthermore, the mechanistic insights into cysteine and dopa detection by silver nanoparticles were investigated using HR-TEM analysis. This induces aggregation in stable silver nanoparticles owing to selective and strong interaction of –SH group of cysteine with silver nanoparticle surface. The biogenic Ag NPs are found to be highly sensitive to amino acids of dopa and cysteine with the diagnosis maximum for both amino acids as low as 0.9 µM (dopa) and 1 µM (cysteine) under optimized conditions.

Synthesis of silver nanoparticles fabricated by leaf extract of Caryota urens and its antioxidant activity

Many studies have been suggested that nanotechnology effects on various science fields. This study was instantiates leaf broth for synthesis of silver nanoparticles. The various physicochemical parameters viz., pH, incubation period, temperature, quality and quantity of leaf extracts and, silver nitrate concentration were influences synthesis of the phyto engineered nanoparticles. Secondary metabolites were present in leaf extract play an important role in the green reduction of the silver ions involved in the capping of the AgNPs during synthesis this study revealed from the FTIR spectroscopic studies. pH 10 influences the formation of brown color and bioreduction of Ag+ to Ag ions observed in surface Plasmon resonance bands developed by UV-Vis spectroscopic studies data revealed that 419 nm. The negative charged particles study revealed by zeta potential. The XRD study reveals that crystalline nature of the nanoparticles and, smallest size of the nanoparticles at highly purity at 2θ 380, lattice peak 111 and 15 nm. The peak was 1383 cm-1 mainly involving the aromatic ring involved In the capping of the AgNPs during phytoreduction. Atomic force microscopic and HR-TEM image reveal that spherical shape and size of the NPs. The size of the nanoparticles is 10-80 nm in scale. Formation of nanofringes describes the high stability in nature. The efficacy of silver nanoparticles on antioxidant activity eas determined by the DPPH assay at different concentrations viz., 12.5, 25, 50, 100, 200 and 400 μg/ml. This investigation revealed that the significant decrease the colour intensity of the reaction mixture, when compared to the standard ascorbic acid. The determined IC50 value of the silver nanoparticles was 50 μg/ml. These results were showed that a significant role in the increasing the radical scavenging activity.

Metabolome, transcriptome and physiological analyses provide insight into the color transition of litchi pericarp

Litchi is popular around the world for its attractive appearance, exotic flavor and rich nutrition, but the pericarp becomes brown rapidly after harvest, which greatly reduces its shelf life and market value. Both metabolites and gene expression were profiled on a large scale in litchi pericarp at four typical color stages covering from preharvest to postharvest. Through a liquid chromatography tandem mass spectrometry approach, 731 metabolites were identified, of which 385 were differentially metabolized. The flavonoid biosynthetic pathway was enriched based on the analysis of differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) among the four stages. In addition, six common types of anthocyanins were identified, among which cyanidin-3-rutinoside and peonidin-3-glucoside were dominant. Surprisingly, the highest accumulation of metabolites, including flavonoids and anthocyanins, was detected at the green stage, and the abundance of metabolites was positively correlated with the expression of structural and regulatory genes related to their biosynthesis. Among the differentially metabolized phytohormones, abscisic acid (ABA) was more accumulated at the turning and brown stages than at the green and red stages. Epicatechin and procyanidin B2 accumulated greatly from the green to red stages, while their relative contents were reduced by 91.51 % and 64.39 %, respectively, at the brown stage compared to the red stage, indicating their pivotal roles in litchi pericarp browning. In summary, the significant decrease in flavonoid content may be the main cause of brown color formation. This study provides an important foundation for future studies on browning prevention and better utilization of litchi pericarp.

Chitin Nanocrystal Hydrophobicity Adjustment by Fatty Acid Esterification for Improved Polylactic Acid Nanocomposites.

Bioplastics may solve environmental issues related to the current linear plastic economy, but they need improvement to be viable alternatives. To achieve this, we aimed to add chitin nanocrystals (ChNC) to polylactic acid (PLA), which is known to alter material properties while maintaining a fully bio-based character. However, ChNC are not particularly compatible with PLA, and surface modification with fatty acids was used to improve this. We used fatty acids that are different in carbon chain length (C4–C18) and degree of saturation (C18:2). We successfully used Steglich esterification and confirmed covalent attachment of fatty acids to the ChNC with FTIR and solid-state 13C NMR. The morphology of the ChNC remained intact after surface modification, as observed by TEM. ChNC modified with C4 and C8 showed higher degrees of substitution compared to fatty acids with a longer aliphatic tail, while particles modified with the longest fatty acid showed the highest hydrophobicity. The addition of ChNC to the PLA matrix resulted in brown color formation that was reduced when using modified particles, leading to higher transparency, most probably as a result of better dispersibility of modified ChNC, as observed by SEM. In general, addition of ChNC provided high UV-protection to the base polymer material, which is an additional feature that can be created through the addition of ChNC, which is not at the expense of the barrier properties, or the mechanical strength.

Antibacterial activity of airborne fungal mediated nanoparticles in combination with Foeniculum vulgare essential oil

Introduction: A cost-effective and ecologically friendly method of generating silver nanoparticles (AgNPs) includes pathways that utilize a variety of biological sources to decrease metal ions. This study was designed to synthesize AgNPs using a fungus strain Aspergillus flavus and evaluate its antibacterial activities alone or in combination with Foeniculum vulgare (fennel) essential oil (EO). Methods: The antibacterial activity of different concentrations of biosynthesized AgNPs by Aspergillus flavus individually and in combination with fennel EO was investigated using disc diffusion methods and minimal inhibitory concentration (MIC). Bacterial species, including Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Enterobacter cloacae, Shigella sp., Staphylococcus aureus, and Staphylococcus epidermidis were tested. Results: Formation of dark brown color, ultraviolet-visible (UV/Vis) spectroscopy, transmission electron microscope (TEM), and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used for the characterization of AgNPs. Obvious synergistic effects were observed between AgNPs and EO of fennel (F. vulgare) with all tested bacteria except S. aureus, through increases in fold area of inhibition (IFAs) within the range of 0.15 to 8.87. Although S. aureus had the most susceptibility toward both AgNPs and EO of fennel (24 and 17 mm, respectively), no synergistic activity was exhibited. The best synergistic capacity resulted from AgNPs and fennel EO was observed against S. epidermidis (8.87-fold in IFA). Conclusion: This study revealed that when biosynthesized AgNPs were mixed with the EO of F. vulgare, they became more bacteriostatic and might be developed to treat bacterial infections in the future.

The Effect of p-Coumaric Acid on Browning Inhibition in Potato Polyphenol Oxidase-Catalyzed Reaction Mixtures.

There has been considerable interest in using natural polyphenol oxidase (PPO) inhibitors to control browning in fruit and vegetable products. p-Coumaric acid (pCA), a common secondary metabolite of plants, has been studied as an inhibitor of PPOs/tyrosinases from several foods (e.g., mushroom, apple, and potato). However, studies on the use of pCA for the inhibition of PPO-initiated browning in actual food systems are limited. Therefore, a study was carried out to ascertain the efficacy of using pCA to limit PPO-initiated browning in fresh potato juice. The extent of browning inhibition by pCA was shown to be reaction system-dependent. Browning in potato juice was unexpectedly enhanced by the addition of pCA. This was interpreted as pCA acting as an alternative substrate with significantly higher browning efficiency; extent of browning under this condition was higher than that observed in the native potato juice. The addition of pCA to any of the model reaction mixtures (i.e., those containing semi-purified enzymes and substrates) significantly inhibited browning. The discrepancy in pCA effects on browning inhibition in different reaction systems is postulated to be mainly due to non-enzyme and non-substrate components in potato juice that participate in the post-PPO reaction sequences, which ultimately lead to brown color formation.

Effect of heat treatment on amino acids and volatile compounds of enzymatic pork trimmings hydrolysate supplemented with xylose and cysteine

In this research, the effects of heat treatment together with xylose and cysteine addition on the amino acid changes and volatile compound generation in non-enzymatic pork trimmings extract (NPE) or enzymatic pork trimmings hydrolysate (EPH) were studied. Enzymatic hydrolysis significantly increased the total amino acid content and provided necessary precursors for the thermal reactions. The addition of xylose assisted the browning process while the cysteine addition partially inhibited the formation of brown colour in both NPE and EPH. The addition of both cysteine and xylose significantly increased the formation of sulfur-containing volatile flavour compounds in EPH samples, but not in NPE samples. The characteristic “roasted meat” like aromatic volatile compounds, in particular, 2-furfurylthiol, were only detected in EPH samples at 8.13 ng/mL, when both xylose (35 mg/mL) and cysteine (10 mg/mL) were added.

Serum Phenoloxidase Activity in the Hemolymph of Giant Freshwater Prawn Macrobrachium rosenbergii (De Man, 1879)

Melanization is one of the major immune responses in arthropods, particularly crustaceans. The prophenoloxidase (proPO) catalyzes the oxidation of mono or di or polyphenols, a reaction that is the key initial step of melanin formation. We attempted to study the immune response in M. rosenbergii by melanization reaction as produced by serum phenoloxidase (PO) activity. The substrate affinity of the PO enzyme was determined using different phenolic substrates and it was found that the mono, di and poly phenols were oxidized hence the enzyme was characterized as catecholoxidase and l-3,4-dihydroxyphenylalanine (L–DOPA) showed the highest substrate affinity to the enzyme. The biochemical parameters that determined optimum enzyme activity were found such as 1 mM L–DOPA concentration showing at the absorbance of 470 nm, 10 mM Tris–HCl buffer pH 7.5 (brown colour formation), temperature 40 ° C and 10 min incubation. Kinetic characteristics of serum from the prawn were also determined. Determination of optimal conditions of PO activity in the serum has also been attempted. We also identified the serum having a potent PO activity was inhibited by phenylthiourea (PTU) and activation of such as trypsin, sodium dodecyl sulphate (SDS) and laminarin in the freshwater prawn M. rosenbergii.

Physicochemical and Microbiological Changes in Non-Sulfitted Dried Apricots as Affected by Storage Condition

The present study was conducted for the determination of physicochemical and microbial quality changes for the non-sulfited sun dried apricots (NSDAs) with three various moisture contents (MCs); 137 g/kg (MC137), 235 g/kg (MC235), and 270 g/kg (MC270); at different temperatures (4, 10, 20, and 30°C) during 12 months in bulk and packaged storage. NSDAs were subjected to physical (moisture, water activity, pH and reflectance color values), chemical (browning formation, β-carotene, and acidity), and microbial (counts for total aerobic mesophilic and psycrofilic bacteria, yeast and mould, xerofilic mould and yeast, osmophilic yeast, lactic acid bacteri, Enterobacteriaceae, Staphylococcus-Micrococcus spp.) analyses at one-month intervals. Results indicated that the fastest brown colour formation occurred in the samples containing 235 g/kg MC at 30°C, and the browning was decelerated below 10°C. No significant change in β-carotene contents of NSDAs during storage was observed (P> 0.05). After rehydration, osmophilic yeast count of NSDAs increased by 2.5 log colony-forming units (cfu/g). Significant reductions were observed in the microbial loads of MC235, and MC270 samples with the decreasing water activity (P<0.05) and increasing storage temperatures. However, yeasts and moulds counts exceeded 5.0 log cfu/g of the samples containing 270 g/kg MC after 2 month of storage at 20°C. Overall, the results of the study suggest that NSDAs should not be stored above 10°C, and the MC should be kept below 235 g/kg to maintain microbial and physicochemical quality.

Green synthesis of silver nanoparticles using aqueous extract of Acacia cyanophylla and its antibacterial activity

AimsThe aim of this research is to conduct green synthesis of silver nanoparticles in an eco-friendly, economical and more effective approach using Acacia cyanophylla plant extract as well as to study the effects of the preparation conditions on the size of synthesized nanoparticles and its antibacterial activity. MethodologyIn this study, silver nanoparticles have been synthesized by reduction method using aqueous silver nitrate solution and aqueous extract of Acacia cyanophylla. Then, their characterization has been studied by several methods, such as visual inspection, UV–Vis spectroscopy, dynamic light scattering and scanning electron microscope. In addition, the effects of (silver nitrate: extract) ratio, type extract, temperature and reaction time have been studied on the size of prepared silver nanoparticles. Furthermore, the antibacterial effect of these nanoparticles was studied on Escherichia coli using micro-dilution method and determination the Minimum Inhibitory Concentration (MIC). ResultsThe results showed that the silver nanoparticles prepared using Acacia cyanophylla extract have reported visible yellowish brown color formation and the absorption peak at 460 nm indicated the biosynthesis of silver nanoparticles. Moreover, they have average diameter (88.11) nm and the polydispersity index (PdI) was suitable. The optimal conditions for synthesis silver nanoparticles were using aqueous extract in 9:1 ratio (silver nitrate: extract) at 35 °C for 48 h. These silver nanoparticles were stable in the in the fridge at 5 °C for a maximum period of 15 days. On the other hand, the antibacterial tests showed that these nanoparticles have high antibacterial activity where the MIC value ranged between (3.125–12.5) μg/ml on E. coli isolates. ConclusionWe conclude that Acacia cyanophylla extract is considered effective as a reducing agent for the preparation of stable silver nanoparticles in certain conditions and this silver nanoparticle has a high antibacterial activity.

Synthesis and Characterization of Chitosan/Silver Nanocomposite Using Rutin for Antibacterial, Antioxidant and Photocatalytic Applications

The present study reports an eco-friendly synthesis of chitosan/silver (CS/Ag) nanocomposite using rutin by a bio-inspired method. The formation of brown color and UV–visible absorbance peak at 415 nm confirmed the synthesis of CS/Ag nanocomposite. X-ray diffraction (XRD) analysis revealed the crystalline peaks of both chitosan and silver in synthesized CS/Ag nanocomposite. Field emission-scanning electron microscopy (FE-SEM) analysis showed that the synthesized CS/Ag nanocomposite having predominant spherical shaped nanostructure with an average size of 23–78 nm. Fourier transform infrared spectroscopy (FTIR) analysis indicated the presence of functional derivatives related to chitosan and rutin in CS/Ag nanocomposite. Synthesized CS/Ag nanocomposite exhibited superior disc diffusion antibacterial activity against Bacillus subtilis and Escherichia coli. The in vitro antioxidant of CS/Ag nanocomposite was evaluated spectrophotometrically by using DPPH method. The percentage of antioxidant activity was increased with increasing concentration of CS/Ag nanocomposite. Furthermore, photocatalytic activity of CS/Ag nanocomposite was evaluated by the removal of methylene blue (MB) dye from aqueous solution under sunlight irradiation. Results showed that the degradation efficiency of MB reached up to 88% after irradiation for 220 min. Thus, the obtained results indicated that the synthesized CS/Ag nanocomposite using rutin can be a promising nanomaterial for multifunctional applications.

Green Synthesis of Silver Nanoparticles Using Some Medicinal Plants

Aims: The green synthesis of silver nanoparticles in an eco-friendly, economical and more effective approach using (Acacia cyanophylla, Phlomis syriaca and Scolymus hispanicus) plants extracts and describing their main chemical properties and study the effect of its chemical composition on producing silver nanoparticles.&#x0D; Methodology: In this study, aqueous and ethanolic extracts of the three plants were evaluated for antioxidant activity using 2,2-diphenyl-l-picrylhydrazyl (DPPH) assay, Total polyphenol and flavonoid contents were determined using spectrophotometric method, but total saponins were determined by weight method, The synthesis of silver nanoparticles was performed by a reduction method using aqueous silver nitrate solution and aqueous extracts of the three plants. Then study its characterization in a number of ways, such as visual inspection, UV-Vis spectroscopy and dynamic light scattering.&#x0D; Results: The results showed that the total phenolic content ranged in extracts between (13.08 ±2.279 to 98.39 ±4.755 mg GAE/g DW). While the total flavonoid contents varied from (19.83 ±2.384 to 121.64 ±6.469 mg RE/g DW. Antioxidant activity was expressed as IC50 and the obtained results ranged from (IC50= 0.027 ±0.00038 to 0.878 ±0.045 mg/ml), the results indicated that the ethanolic Acacia cyanophylla extract from the six examined extracts showed the highest phenolic and flavonoid concentration and strong antioxidant activity. Also, the saponins content in the three plants ranged from (0.46 to 2.53)% and the highest amount of saponins reported in Acacia cyanophylla plant. The silver nanoparticles prepared using Acacia cyanophylla extract have reported visible yellowish brown color formation and the absorption peak at 460 nm indicates the biosynthesis of silver nanoparticles and they have average diameter (134.1) nm and the polydispersity index (PdI) was suitable (0.260).&#x0D; Conclusion: Acacia cyanophylla extract has been considered as the best reducing agent among the selected plant extracts for the preparation of stable colloidal silver nanoparticles, this is due to their high content of flavonoids, phenols and saponins.

Browning of Epicatechin (EC) and Epigallocatechin (EGC) by Auto-Oxidation.

Green tea catechins are well known for their health benefits. However, these compounds can easily be oxidized, resulting in brown color formation, even in the absence of active oxidative enzymes. Browning of catechin-rich beverages, such as green tea, during their shelf life is undesired. The mechanisms of auto-oxidation of catechins and the brown products formed are still largely unknown. Therefore, we studied auto-oxidative browning of epicatechin (EC) and epigallocatechin (EGC) in model systems. Products of EC and EGC auto-oxidation were analyzed by reversed-phase ultra-high-performance liquid chromatography with photodiode array detection coupled to mass spectrometry (RP-UHPLC-PDA-MS). In the EC model system, 11 δ-type dehydrodicatechins (DhC2s) and 18 δ-type dehydrotricatechins (DhC3s) that were related to browning could be tentatively identified by their MS2 signature fragments. In the EGC model system, auto-oxidation led to the formation of 13 dihydro-indene-carboxylic acid derivatives and 2 theaflagallins that were related to browning. Based on the products formed, we propose mechanisms for the auto-oxidative browning of EC and EGC. Furthermore, our results indicate that dimers and oligomers that possess a combination of an extended conjugated system, fused rings, and carbonyl groups are responsible for the brown color formation in the absence of oxidative enzymes.

Extracellular green synthesis of chitosan-silver nanoparticles using Lactobacillus reuteri for antibacterial applications

Abstract In this work, we report the eco-friendly green synthesis of hybrid chitosan-silver nanoparticles (CS-AgNPs) using Lactobacillus reuteri ATCC 55730. The cell free extracellular biomass of L. reuteri was used as a reducing and capping agent for the synthesis of CS-AgNPs. The synthesized CS-AgNPs were characterized by using UV–visible spectroscopy, X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy, and fourier transform infrared spectroscopy (FTIR). The formation of brown color and UV–visible absorbance peak (λmax) at 415 nm confirmed the synthesis of CS-AgNPs. XRD analysis revealed the face centred cubic crystalline structure of CS-AgNPs. FE-SEM analysis showed that the synthesized CS-AgNPs having quasi-spherical shaped nanostructure with an average size of 40–90 nm. The IR bands at 1465, 1543 and 1651 cm−1 indicated the presence of amine groups (-NH2), which confirmed the presence of CS in synthesized CS-AgNPs. The synthesized CS-AgNPs showed potential disc diffusion antibacterial activity against B. subtilis and E. coli pathogens. Furthermore, cotton fabrics impregnated with CS-AgNPs also showed bactericidal zone of inhibition against B. subtilis. Thus, the obtained results exposed that the synthesized CS-AgNPs using L. reuteri can be used against bacterial pathogens in textile industries.