Scientific journal

57 2018

Journal of Food and Nutrition Research
Summary No. 1 / 2018

Savic-Gajic, I. M. – Savic, I. M. – Nikolic, V. D.
Modeling and optimization of quercetin extraction and biological activity of quercetin-rich red onion skin extract from Southeastern Serbia
Journal of Food and Nutrition Research, 57, 2018, No. 1, s. 15-26

Ivana M. Savic-Gajic, Department of Organic-technological Sciences, Faculty of Technology, University of Nis, Bulevar oslobodjenja 124, 16000 Leskovac, Serbia. Tel.: +381 16 247 203; fax: +381 16 242 859, e-mail:

Received 27 June 2017; accepted 2 November 2017; published online 11 February 2018

Summary: Quercetin is a bioactive compound that has the beneficial effect on human health because of its antioxidant, anti-inflammatory, antimicrobial, antiviral, antiallergic, cardioprotective, vasodilatatory and anticancer activity. Due to high content of quercetin in the red onion skin, the aim of this study was modelling and optimization of quercetin extraction using central composite design. The extraction time (5–60 min), ethanol concentration (5–100%) and liquid-to-solid ratio (10–80 cm3·g-1) were varied to estimate their effect on the yield of quercetin. The optimal extraction conditions were obtained for 47.3 min using 80% ethanol adjusted to pH 1.0 at a liquid-to-solid ratio of 63.9 cm3·g-1. In the extract obtained under these conditions, the quercetin content was found to be 28.5 g·kg-1 of the dry plant material, while the content of total flavonoids and polyphenols was found to be 30.1 g rutin equivalent per kilogram of the dried extract and 53.82 g gallic acid equivalent per kilogram of the dried extract, respectively. The studies of the antioxidant ac­tivity indicated that quercetin had a higher activity than the extract enriched with quercetin. Quercetin was also isolated from the extract by the liquid-liquid extraction technique and structurally characterized using instrumental methods.

Keywords: central composite design; total flavonoid; total polyphenol; antioxidant activity

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