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    Chemical and biological insights on aronia stems extracts obtained by different extraction techniques: From wastes to functional products
    (ELSEVIER SCIENCE BV, 2017) Cvetanovic, Aleksandra; Svarc-Gajic, Jaroslava; Zekovic, Zoran; Maskovic, Pavle; Durovic, Sasa; Zengin, Gökhan; Delerue-Matos, Cristina
    The present study aimed to evaluate chemical and biological potential of aronia stems for providing new raw material for food and pharmaceutical industries. Aqueous extracts of aronia stems were prepared by three different techniques (microwave-assisted, ultrasound-assisted and subcritical water extraction). For biological activities, antioxidant, antimicrobial and cytotoxic activities were evaluated. For chemical characterisation, phenolic compounds and essential elements were analysed as well as total phenolic contents. Subcritical water extracts exhibited the strongest antioxidant activity with the highest content of phenolics. Minimum inhibitory concentrations for analysed extracts were in the range from 9.76 to 156.25 mu g/mL in antimicrobial assays. The extracts exerted prominent cytotoxicity against different cell lines. Rutin was detected as the major compound in the studied extracts and these extracts were also rich in essential elements. Our study suggested that subcritical water extract of aronia stem could be considered as a new raw material in developing novel functional/industrial products.
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    Effects of Orange Leaves Extraction Conditions on Antioxidant and Phenolic Content: Optimization Using Response Surface Methodology
    (TAYLOR & FRANCIS INC, 2018) Uysal, Şengül; Cvetanovic, Aleksandra; Zengin, Gökhan; Durovic, Sasa; Zekovic, Zoran; Aktümsek, Abdurrahman
    In the last few years, bioactive components or their extraction techniques are gaining special interest in scientific areas. In this framework, orange leaves were used for preparation of extracts with high content of biologically active compounds. To optimize the extraction process, three levels and three variables of Box-Behnken design with response surface methodology were applied. Investigated responses were the total phenolic content (TPC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, cupric ion reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP). Independent variables were methanol concentration (10-90%), temperature (20-60 degrees C), and extraction time (60-180min). Experimentally obtained results were fit into a second-order polynomial model with multiple regression. Analysis of variance was used to estimate model fitness and determine optimal conditions for processing. Estimated optimal conditions were 90% methanolic solution, 60 degrees C and 180min using these parameters; the predicted values of investigated responses were 43.19mg GAE/g (GAE: gallic acid equivalents), 43.04mg TE/g (TE: trolox equivalents), 139.34 and 93.76mg TE/g for TPC, DPPH, CUPRAC, and FRAP, respectively. The obtained optimal conditions could be considered as an alternative strategy for developing novel functional products.
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    Isolation of apigenin from subcritical water extracts: Optimization of the process
    (ELSEVIER SCIENCE BV, 2017) Cvetanovic, Aleksandra; Svarc-Gajic, Jaroslava; Gasic, Uros; Tesic, Zivoslav; Zengin, Gökhan; Zekovic, Zoran; Durovic, Sasa
    Apigenin is a phytochemical which has been associated with numerous beneficial health effects. However, due to its low concentration and poor bioavailability, isolation from natural sources is very difficult. Subcritical water (SCW) is an excellent solvent for the extraction of moderately polar and non-polar flavonoids. Carefully balanced moderate hydrolytical potential of SCW was used in this work to liberate apigenin from its bound forms. In this research simultaneous extraction and hydrolysis of apigenin bound forms from chamomile have been performed. Optimal operation parameters for maximum yields of apigenin have been investigated and defined (solvent-to-sample ratio 1:30; agitation rate 3 Hz; pressure 45 bar; temperature 115 degrees C; time 30 min). Apigenin was further isolated in its pure form from water extracts obtained under optimal conditions using column chromatography. The purity of isolated compound was confirmed by spectroscopic analysis. Biological activity of extracts obtained under optimal conditions were determined as well. In order to identify polyphenolic compounds UHPLC-HESI-MS/MS analysis was performed. (C) 2016 Elsevier B.V. All rights reserved.
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    Optimization of the extraction process of antioxidants from loquat leaves using response surface methodology
    (WILEY, 2017) Uysal, Şengül; Cvetanovic, Aleksandra; Zengin, Gökhan; Durovic, Sasa; Aktümsek, Abdurrahman
    This study is designed to optimize the extraction of polyphenolics and antioxidant potential of loquat leaves using response surface methodology (RSM). Three levels and three variables Box-Behnken experimental design in combination with RSM was applied. Independent variables were solvent concentration (10-90%), temperature (20-60 degrees C) and time (60-180 min), while investigated response was total phenolic content as well as antioxidant activity. The experimental results were fitted to a second-order quadratic polynomial model, and they showed a good fit to the proposed model. In order to assess model fitness and determine optimal conditions, for maximal phenolic content and antioxidant activity, analysis of variance was employed. Determined optimized conditions for maximizing yield of antioxidant compounds were within the experimental range: ethanol concentration of 88.4%, extraction temperature of 28 degrees C, extraction time of 70.8 min. Under these conditions, the predicted maximum values were TP-77.18 mg GAE/g, DPPH-80.42 mg TE/g, CUPRAC-308.87 mg TE/g and FRAP-164.12 mg TE/g. Practical applicationsPlant phenolics have remarkable biological activities including antioxidant, antimicrobial and anticancer. Therefore, their extraction techniques have gained more attention in recent years. This study was designed to detect optimal extraction conditions of independent factors (i.e. solvent concentration, temperature and time) in order to obtain the highest yields of phenolics from loquat leaves as well as antioxidant activity. This study could be valuable for designing new nutraceutical and functional food ingredients in terms of high recovery of phenolics from loquat leaves.