Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem An environmentally friendly method based on micro-cloud point extraction for determination of trace amount of quercetin in food and fruit juice samples Rouhollah Khani ⁎ , Raziye Sheykhi, Ghodsieh Bagherzade University of Birjand, Faculty of Science, Department of Chemistry, Birjand 97179-414, Iran ARTICLE INFO Keywords: Quercetin Flavonoid Micro-cloud point extraction Spectrophotometry Experimental design ABSTRACT This study was conducted for quantitative determination of quercetin in food and fruit juice samples based on a green, fast, and accurate method namely, micro-cloud point extraction (MCPE). The proposed MCPE is essen- tially a miniaturized form of traditional cloud point extraction (CPE) in which only a few microliters of micellar extracting phase is sufcient for determination. Factors infuencing the extraction efciency, such as amount of Triton X-114 (5%, v/v), efect of pH, amount of Na 2 SO 4 salt (5%, w/v) and time of centrifugation were in- vestigated and optimized by experimental design. Under the optimized condition, the calibration range was found to be linear over 10–100 ng mL −1 with the limit of detection of 2.2 ng mL −1 . The relative standard de- viation of 2.8%, was obtained on a 30 ng mL −1 quercetin standard solution (n = 3). Finally, the proposed method was successfully applied for the determination of quercetin in onion, tomato, apple and orange juice samples. 1. Introduction The favonoids of dietary signifcance are widely distributed in the plant kingdom and can be categorized as favones, favanones, and anthocyanin’s (Biesaga & Pyrzynska, 2009). Flavonoids compounds, which play an important role as natural potent antioxidants, exhibit various biological and physiological activities, such as anti-allergic, anti-infammatory and anti-carcinogenic activities, in the human me- tabolic system (Fiorucci, Golebiowski, Cabrol-Bass, & Antonczak, 2007). The anti-oxidative activity of favonoids depends on the position and the number of hydroxyl (Budeˇjovice, 2001). Evidence has shown that favonoids are capable of modulating the activity of enzymes and afecting the behavior of many cell systems (Sun, Zhang, Li, & He, 2013). Quercetin or 2-(3, 4-dihydroxyphenyl)-3, 5, 7-trihydroxy-4H- chromen-4-one (QR), is one of the most abundant biofavonoids found in many plant sources and food samples such as onions, tea, apples (Wach, Pyrzyńska, & Biesaga, 2007; Usoltseva, Samarina, Abramchuk, Prokhorova, & Beklemishev, 2016). Antioxidant efect of QR implied to be helpful for human health. QR shows heavy antioxidant activity, due to free radical scavenging, and can protect human DNA from oxidative attack in vitro (Saber-Tehrani, Pour Habib, Husain, & Arvand, 2013). The epidemiological studies have shown that QR exhibits anti-cancer, anti-infammatory, stabilizes cell membranes, antihistamine, anti-al- lergic, anti-edematous, antiviral activity, and may prevent cardiovascular illness in humans (Xiao, Zhao, & Zeng, 2007). Based on the terms stated, the determination of QR has been interesting research area in last decade. Several methods have been introduced for the determination of QR by High-performance liquid chromatography (HPLC) with fuorescent (Biasutto, Marotta, Garbisa, Zoratti, & Paradisi, 2010), chemilumines- cence (CL) (Wu, Chen, Fan, Elsebaei, & Zhu, 2012) and mass spectro- metry (MS) (Del Mar Castro-Lopez, Lopez-Vilarino, & González- Rodríguez, 2014) detection, capillary electrophoresis (Chi et al., 2009), spectrophotometry (Yola & Atar, 2014) and electrochemical methods (Gupta et al., 2015). In addition, High-performance capillary electro- phoresis (HPCE) was used for determination of the pharmacologically active favonoids in ginkgo balboa and phytopharmaceuticals (Kurzawa, 2010). Despite sensitivity and efciency of the mentioned method, complexity of the operation, reagent-consuming, and high cost as these method’s disadvantages reduced its popularity. MCPE in combination with UV–Vis spectrophotometry was proposed as a green, fast, simple, inexpensive and environmentally friendly method. This method used for the preconcentration and determination of QR to overcome to all problems. In MCPE, the consumption of organic sol- vents is reduced to 40–50 μL, which makes this method even more environmental friendly (Ghasemi & Kaykhaii, 2016). The method was fnally applied to the determination of quercetin in several categories of food samples. https://doi.org/10.1016/j.foodchem.2019.04.099 Received 21 July 2018; Received in revised form 4 April 2019; Accepted 25 April 2019 ⁎ Corresponding author. E-mail address: Rouhollah.khani@birjand.ac.ir (R. Khani). Food Chemistry 293 (2019) 220–225 Available online 25 April 2019 0308-8146/ © 2019 Elsevier Ltd. All rights reserved. T