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Faculty of Applied Sciences

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Subject: search.filters.subject.Antioxidant activities

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    Green synthesis of silver nanoparticles using flower extracts of Aerva lanata and their biomedical applications
    (Informa UK Limited, 2022-01-02) Palithya, Sashikiran; Gaddam, Susmila Aparna; Kotakadi, Venkata Subbaiah; Penchalaneni, Josthna; Golla, Narasimha; Krishna, Suresh Babu Naidu; Naidu, C.V.
    In the present study, green synthesis of silver nanoparticles (AgNPs) was performed using flower extracts of Aerva lanata (Al) from Amaranthaceae family. The size, shape, and elemental composition of the silver nanoparticles (AgNPs) was studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and UV-visible spectroscopy. The dynamic light scattering (DLS), of silver nanoparticles (AgNPs) exhibited mean size of 7.6 nm in the range of 5–15 nm, having a poly-dispersed indexed value of 0.419. Zeta potential contributing to the stability of silver nanoparticles was recorded as −18.7 mV. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis confirmed the presence of the synthesized AgNPs with an average size range 7 ± 3 nm. The biosynthesized silver nanoparticles displayed antibacterial activity against Gram-positive and Gram-negative bacteria. The 2,2’-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay revealed antioxidant potential of silver nanoparticles in the concentration of 100 µg/ml. The photocatalytic activity of silver nanoparticles was evaluated using decolourization of the dyes under the sunlight using UV-Vis. spectroscopy. The results suggest that biosynthesized silver nanoparticles from A. lanata (Al-AgNPs) flower extracts have broad spectrum antibacterial, antioxidant and catalytic activities may be useful in a variety of biomedical and industrial applications.
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    An investigation of the voltammetric behaviour of antioxidants in flavonoids
    (2020-04) Ramsarup, Lee-Ann; Bisetty, Krishna; Kanchi, Suvardhan
    The two case studies in this work involve the development and fabrication of an electrochemical biosensor using various enzymes for the evaluation of the electrochemical responses, relating to the total phenolic (TP) content and the antioxidant activities in wine and tea samples respectively. The modification of the glassy carbon electrode (GCE) was carried out using green apple as an enzymatic source of polyphenol oxidase and laccase enzyme. The experimental variables were optimized using the Box-Behnken experimental design as a predictive model, for a better understanding of the parameters and their interaction responses with each other during an electrochemical analysis. This multivariate optimization method is based on a factorial design, where the three most influential factors include the electrolyte pH, the deposition time (td) and the scan rate (sr). The design was run in a single block fashion while random order of experiment was selected to provide greater protection against the effects of outlying variables. The optimized results obtained yielded the most suitable conditions for the determination of the TP content in wine samples. They were selected as follows: phosphate buffer of pH 7.65 as supporting electrolyte, td 29.8 s and sr 25.0 mV/s respectively. The method was optimized for the current signal at a deposition potential of 0.2 V and within an oxidation potential of -0.2 V to 0.6 V. Good analytical responses were obtained with apple sensors for the detection of TP content in wine samples, with a higher concentration in red wines than in white wines. Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were used to establish and interpret the redox mechanisms of flavonoids present in alcoholic and non-alcoholic beverages. The sensor responses were evaluated by first, investigating the changes in the total phenolic (TP) content in wine samples using catechin as a standard. Thereafter, the electrochemical behaviour of rutin and ascorbic acid, antioxidant capacities (trolox reagents) were established in tea samples, yielding a positive linear correlation between the trolox equivalent antioxidant capacities (TEAC) and TP content (R2 = 0.9812 ± 0.012). DPV was applied to the laccase modified GCE, and the experimental results indicate that this sensor shows good reducing properties. The scavenging ability of 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) a diammonium salt, was assessed in the sample extracts, which yielded half-maximal effective concentration (EC50) values of 10.80 μg/ml and 11.62 μg/ml for ascorbic acid and rutin respectively. These findings indicated that the experimental design was a convenient method to evaluate the statistical significance of the optimised parameters, and the positive linearity for the TEAC and the TP content confirms the robustness of this methodology.