BK21 Research Team for Developing Functional Health Food Materials, Kyungpook National University, 1370, Sankyuk-Dong, Daegu 702-701, Republic of Korea.
Food Chem Toxicol. 2012 Jun;50(6):2042-8. doi: 10.1016/j.fct.2012.03.065. Epub 2012 Apr 1.
Yellow onion (Allium cepa) extract showed enhanced antioxidative effects in 2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox equivalent antioxidant capacity (TEAC) and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and acetyl ester (CM-H(2)DCFDA) assay after being treated with a crude enzyme extract from soybean paste fungi, Aspergillus kawachii. HPLC analysis showed two increased and two decreased peaks after enzyme treatment. The decreased peaks were identified as quercetin-3,4'-di-O-β-d-glucoside (1) and quercetin-4'-O-β-d-glucoside (2), and peaks that increased were quercetin-3-O-β-d-glucoside (3) and quercetin (4), respectively. It was expected that 3 and 4 were originated from the glucosidic cleavage of their glucosides, 1 and 2. Among the increased compounds, only quercetin (4) showed strong antioxidative activity in the DPPH assay. In addition, the protective effect against glutamate-induced neurotoxicity in HT22 cells was increased when treated with 25 μg/ml of fermented onion. The enhanced neuroprotective effect was also originated from the increased quercetin content. As a consequence, fermentation raised the quercetin content in onion, and subsequently increased the antioxidative and neuroprotective activities.
黄洋葱（Allium cepa）提取物经豆酱真菌米曲霉（Aspergillus kawachii）粗酶提取物处理后，在 2,2-二苯基-1-苦基肼（DPPH）、Trolox 等效抗氧化能力（TEAC）和 5-（和-6）-氯甲基-2'，7'-二氯二氢荧光素二乙酸酯和乙酰酯（CM-H（2）DCFDA）测定中显示出增强的抗氧化作用。HPLC 分析显示酶处理后有两个增加的峰和两个减少的峰。减少的峰被鉴定为槲皮素-3,4'-二-O-β-d-葡萄糖苷（1）和槲皮素-4'-O-β-d-葡萄糖苷（2），增加的峰分别为槲皮素-3-O-β-d-葡萄糖苷（3）和槲皮素（4）。预计 3 和 4 是由 1 和 2 的糖苷的糖苷键裂解产生的。在所增加的化合物中，只有槲皮素（4）在 DPPH 测定中表现出强烈的抗氧化活性。此外，当用 25μg/ml 发酵洋葱处理时，HT22 细胞中谷氨酸诱导的神经毒性的保护作用增加。增强的神经保护作用也源自增加的槲皮素含量。因此，发酵提高了洋葱中的槲皮素含量，从而提高了抗氧化和神经保护活性。
