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Today, nanosilver is one of the most commercialized nanomaterials. The demand for synthesis of Nanosilver through biocompatible routs due to wide biomedical application has increased. Use of plants and plant products as sustainable and renewable resources in the synthesis of nanoparticles is more advantageous over other biological routes. In this study, biosynthesis of silver nanoparticles (AgNPs) using aqueous extract of Withania somnifera as reducing agent is reported. Effect of parameters such as AgNO3 concentration, aqueous extract, pH and formation time were investigated and optimized by UV-visible spectroscopy in the synthesis of nanoparticles. At room temperature, the solution color started to change from pale yellow to dark brown due to the reduction of silver ion. The transmission electron microscopy (TEM) was applied for size and morphological analysis of nanoparticles. TEM result shows a spherical structure with an average size ranging from 24-35 nm for silver nanoparticles.
 

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Nowadays, extensive investigations have been conducted on developing novel biopolymers from biodegradable sources. In the current study, the active packaging film based on sago starch-containing varying concentrations (1, 1.5 and 2 MIC) of Withania Somnifera L. extract were produced. The Minimal Inhibitory Concentration (MIC) and Minimal Bactericide Concentration (MBC) of extract were measured. Physicochemical (such as thickness, water absorption capacity (WAC), water solubility (WS), water vapor permeability, Oxygen Permeability (OP) and contact angle (CA)), mechanical (tensile strength, elongation to break and modulus of elasticity) and antioxidant properties of the films were evaluated. The antibacterial activity of the films also was tested against two common food-borne pathogens (Escherichia coli, and Staphylococcus aureus) by the disc diffusion method. The results showed that increasing concentrations of Withania Somnifera L. extract have a significant effect (p <0.05) to increase the amount of thickness, WS, water vapor permeability, OP, and CA, but was not effective on WAC. Withania Somnifera L. extract increased the absorption of color in the visible region, which in turn led to an increasing of the parameters a^* (index color tends toward green) and b^* (index color tends towards yellow) but reduced L^*. An increase in Withania Somnifera L. extract content resulted in a plasticizing effect, reducing the tensile strength and Young’s modulus but a concurrent increase in elongation at break. Sago films containing higher percentages of Withania Somnifera L. extract were effective against all two tested bacterial strains, and these effects were more significant in the case of the gram-positive bacteria. Sago film containing extract showed a good DPPH radical scavenging activity. These results suggest that the developed sago films containing Withania Somnifera L. extract could be used in various food packaging applications.

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Nowadays, the food industry is looking for new technologies to increase the shelf life of various products. Furthermore, as consumer's demand for more “healthier” meals (free of conventional chemical preservatives) has increased in the last decade. In this study, edible sago starch coating containing leave extract of Withania Somnifera (0.125 and 0.25 mg/ml, 1 and 2 times MIC, respectively) was applied onto chicken fillet to extend its shelf life at 4 ˚C. Examination of coated chicken fillets showed that active film of sago starch inhibited the microbial load (aerobic bacteria, coliform and Staphylococcus aureus bacteria) of chicken fillets. The results of chemical analysis of chicken fillet also showed that the coated samples had less volatile nitrogen compounds, thiobarbituric acid index and peroxide value than control. In general, the results of this study showed that the edible film produced from sago starch containing Withania Somnifera extract increases the shelf life of chicken fillets.

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In the present study, the hydroalcoholic extract of Withania somnifera was extracted and then the content of total phenol (by Folin-Ciocalteu reagent), total flavonoid (by aluminum chloride method), antioxidant activity (based on DPPH and ABTS free radical scavenging methods) and its antifungal effect against Rhizopu stolonifers, Botrytis cinerea, Penicillium expansum and Alternaria alternata (fungi cause spoilage postharvest apple and strawberry fruits) were determined based on disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration. The amount of phenol and flavonoids in the extract was 53.16 mg GAE/g and 28.20 mg QE/g, respectively. The antioxidant power of the hydroalcoholic extract was 69.80 and 57.15 μg/ml in terms of DPPH and ABTS free radical scavenging, respectively. The results of antimicrobial activity based on disk diffusion agar and well diffusion agar showed that increasing the concentration of the extract caused a significant increase in the diameter of the growth inhibition zone and Botrytis cinerea and Alternaria alternata were the most resistant and sensitive strains to the extract, respectively. In general, Penicillium expansum and Alternaria alternata were more sensitive than Rhizopus stolonifer and Botrytis cinerea with minimum inhibitory and fungicidal concentrations of 16 and 128 mg/ml, respectively.