Department of Food Science and Technology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia.
Department of Food Engineering, Faculty of Food Technology and Biotechnology, University of Zagreb, 10000 Zagreb, Croatia.
Int J Mol Sci. 2020 Apr 21;21(8):2909. doi: 10.3390/ijms21082909.
There is increasing concern for reduction of the ecological impacts of industrial waste caused by fruits and vegetables. To reduce costs of onion waste disposal while obtaining value-added products, onion skin can be used to extract quercetin, a natural flavonoid with antioxidant, anti-inflammatory and anti-cancer effects. The aim was to optimize quercetin extraction from brown onion ( L.) skin through investigation of the effects of different parameters on quercetin yield. Operational parameters for conventional maceration extraction and for ultrasound-assisted extraction were compared: solvent type, mass-to-liquid ratio, extraction time and temperature. Antioxidant capacity was determined using DPPH· radical scavenging assays and quercetin yield using HPLC/DAD. Anti-α-amylase activity of onion skin extracts was investigated using α-amylase inhibition assays. Optimal extraction conditions of quercetin from onion skin were obtained with maceration extraction, 50% ethanol, 1:100 mass-to-liquid ratio, 25 °C, for 15 min. Under these conditions, the antioxidant capacity (expressed as quercetin equivalents) was 18.7 mg/g and the mass fraction of quercetin was 7.96 mg/g. The onion skin extracts showed a dose-dependent relationship between dry extract concentration and α-amylase inhibition, which confirms that this onion skin extract can be considered as an anti-diabetes agent.
人们越来越关注减少水果蔬菜工业废料对生态的影响。为了降低洋葱废料处理成本并获得增值产品，可以利用洋葱皮提取槲皮素，这是一种具有抗氧化、抗炎和抗癌作用的天然类黄酮。本研究旨在通过考察不同参数对槲皮素产率的影响，优化从褐皮洋葱（L.）皮中提取槲皮素的方法。比较了常规浸渍提取和超声辅助提取的工艺参数：溶剂类型、料液比、提取时间和温度。采用 DPPH·自由基清除试验测定抗氧化能力，采用 HPLC/DAD 测定槲皮素产率。采用α-淀粉酶抑制试验研究洋葱皮提取物对α-淀粉酶的抑制活性。从洋葱皮中提取槲皮素的最佳条件为浸渍提取，使用 50%乙醇，料液比 1:100，25°C，提取 15 分钟。在此条件下，抗氧化能力（以槲皮素当量表示）为 18.7mg/g，槲皮素质量分数为 7.96mg/g。洋葱皮提取物的干提取物浓度与α-淀粉酶抑制作用之间呈剂量依赖性关系，这证实了这种洋葱皮提取物可以被认为是一种抗糖尿病药物。
