Karami Farahnaz, Ghorbani Mohammad, Sadeghi Mahoonak Alireza, Pourhossein Alireza, Bagheri Ahmad, Khodarahmi Reza
Department of Food Science and Technology, Gorgan University of Agricultural Sciences and Natural Resources, Basij street, 4918943464 Gorgan, Iran.
Medical Biology Research Center, Kermanshah University of Medical Sciences, Daneshgah street, 6714415185 Kermanshah, Iran.
Food Technol Biotechnol. 2022 Dec;60(4):458-468. doi: 10.17113/ftb.60.04.22.7443.
Food by-products such as onion peels and olive leaves are rich in bioactive compounds applicable as natural and low-cost sources of antioxidants. Still, these compounds mainly exist in glycosylated form. Often, hydrolysis of glycoside compounds increases their antioxidant activity and health benefits. However, not many studies have been done concerning the β-glucosidase effect, specifically from , on glycosylated compounds within these by-products. Also, changes in the antioxidant activity of the mentioned by-products under the effect of β-glucosidase have not been reported yet. Therefore, this study considers the effect of β-glucosidase on glucoside compounds and the antioxidant activity of onion peel and olive leaf extracts.
The antioxidant activity of the extracts was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Also, glucose, total phenolic and flavonoid contents were measured. Moreover, TLC and HPLC analyses were performed before and after the enzymatic hydrolysis.
The obtained results showed an increase in the extract antioxidant activity after treatment. Also, β-glucosidase increased the glucose content of the extracts. The thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) results showed the β-glucosidase efficacy to hydrolyze quercetin glucosides in onion peel extract, and the quercetin concentration increased from (0.48±0.04) mg/mL in the untreated extract to (1.26±0.03) mg/mL in the treated extract (0.5% /) after 3 h of enzymatic hydrolysis at 45 °C. Also, the content of quercetin-3-O-glucoside increased considerably from (1.8±0.1) to (54±9) µg/mL following the enzyme treatment. Moreover, oleuropein in olive leaf extract (1% /) was hydrolyzed completely from (0.382±0.016) to 0 mg/mL by β-glucosidase for 24 h at 50 °C.
This study showed that β-glucosidase, as a stable enzyme, hydrolyzed quercetin and oleuropein glycosides in onion peel and olive leaf extracts. Thus, β-glucosidase is a good candidate for processing the food waste and extracting valuable bioactive compounds. Also, the treated extracts with higher antioxidant and biological activity, and without bitter taste can be applicable as potent, natural and cost-effective antioxidants in the food industry.
洋葱皮和橄榄叶等食品副产品富含生物活性化合物，可用作天然且低成本的抗氧化剂来源。然而，这些化合物主要以糖基化形式存在。通常，糖苷化合物的水解会增加其抗氧化活性和健康益处。然而，关于β-葡萄糖苷酶的作用，特别是来自[具体来源未提及]的β-葡萄糖苷酶对这些副产品中糖基化化合物的作用，相关研究并不多。此外，尚未有关于β-葡萄糖苷酶作用下上述副产品抗氧化活性变化的报道。因此，本研究考察了β-葡萄糖苷酶对糖苷化合物以及洋葱皮和橄榄叶提取物抗氧化活性的影响。
通过1,1-二苯基-2-苦基肼（DPPH）和铁还原抗氧化能力（FRAP）测定法测定提取物的抗氧化活性。此外，还测定了葡萄糖、总酚和黄酮含量。此外，在酶促水解前后进行了薄层色谱（TLC）和高效液相色谱（HPLC）分析。
所得结果表明处理后提取物的抗氧化活性有所提高。此外，β-葡萄糖苷酶增加了提取物中的葡萄糖含量。薄层色谱（TLC）和高效液相色谱（HPLC）结果表明，β-葡萄糖苷酶能够有效水解洋葱皮提取物中的槲皮素糖苷，在45℃酶促水解3小时后，槲皮素浓度从未处理提取物中的（0.48±0.04）mg/mL增加到处理后提取物中的（1.26±0.03）mg/mL（0.5%[具体酶浓度未提及]）。此外, 酶处理后，槲皮素-3-O-葡萄糖苷的含量从（1.8±0.1）大幅增加到（54±9）μg/mL。此外，在50℃下，β-葡萄糖苷酶作用24小时后，橄榄叶提取物（1%[具体酶浓度未提及]）中的橄榄苦苷从（0.382±0.016）完全水解至0 mg/mL）。
本研究表明，β-葡萄糖苷酶作为一种稳定的酶，能够水解洋葱皮和橄榄叶提取物中的槲皮素和橄榄苦苷糖苷。因此，β-葡萄糖苷酶是处理食品废料和提取有价值生物活性化合物的良好候选者。此外，经处理的提取物具有更高的抗氧化和生物活性，且无苦味，可作为食品工业中高效、天然且经济高效的抗氧化剂。
