苦荞芽菜游离酚、结合酚及抗氧化活性研究

Free and Bound Phenolic Compounds and Antioxidant Activities in Tartary Buckwheat Sprouts

以苦荞品种‘昭苦2号’籽粒为试验材料,采用高效液相色谱(HPLC)等化学技术研究苦荞芽菜形成过程中多酚物质的含量、组成及抗氧化活性的动态变化,为苦荞芽菜的深度加工提供可靠依据。结果表明,苦荞籽粒萌发到芽菜形成过程中,多酚和黄酮的含量显著升高,总酚和总黄酮含量在萌发2~6 d快速提高,在第6天分别达到109.27 mg/g和137.73 mg/g。游离酚和游离黄酮含量的变化趋势与总酚和总黄酮一致,萌发至第6天分别是萌发前苦荞籽粒的4.08倍和4.53倍。芽菜形成过程中,结合酚和结合黄酮的含量显著提高,但与总酚和总黄酮的比值较小。在苦荞籽粒萌发前后提取物中鉴定出6种黄酮单体,分别为芦丁、槲皮素、表儿茶素、山奈酚、山奈酚-3-芸香糖苷和槲皮素-3-O-芸香糖苷-3′-O-吡喃葡萄糖苷。游离态提取物中主要的黄酮类物质是芦丁和槲皮素,其中芦丁的含量在萌发6~7 d增加缓慢,第6天达到50.80 mg/g,而槲皮素的含量在萌发1 d后不断降低。结合态提取物中主要的黄酮类物质是表儿茶素和芦丁。利用DPPH自由基法、ABTS自由基法和铁离子还原抗氧化法(FRAP)综合评价不同萌发期苦荞提取物的抗氧化活性,发现苦荞籽粒萌发后游离、结合及总抗氧化活性均显著提高。表明萌发至第6天的苦荞芽菜具有更广的市场应用价值。

After germination of the tartary buckwheat variety of‘Zhaoku 2’,phenolic contents,composition contents and antioxidant activities in tartary buckwheat sprouts were investigated by chemical techniques of high-performance liquid chromatography.The contents of phenols and flavonoids increased significantly in growing sprouts after seed germination.The Phenolic and flavonoid totals rapidly increased 2-6 d after seed germination,it reached 109.27 mg/g and 137.73 mg/g at the 6th germination day,respectively.Herein,the contents of free phenols and flavonoids tended to vary consistently in phenol and flavonoid totals,which was 4.08 and 4.53 times in tartary buckwheat seeds at the 6th germination day,respectively.The contents of bound phenols and flavonoids significantly increased in sprouts after germination,but it was relatively lower than the contents of free phenols and flavonoids in seeds before germination.Six flavonoids,rutin,quercetin,epicatechin,kaempferol,kaempferol-3-rutinoside and quercetin-3-O-rutinoside-3′-O-glucopyranoside,were identified in the seed extracts of tartary buckwheat before and after germination.The main flavonoids in the free extracts mainly were rutin and quercetin,which the content of rutin slowly increased 6-7 days after seed germination,it reached 50.80 mg/g at the 6th germination day,and the content of quercetin continuously reduced aftercthe 1st germination day.The main flavonoids in the bound extracts were epicatechin and rutin.Antioxidant activities in the extracts of tartary buckwheat at different germination stages were assessed by the DPPH free radical method,ABTS free radical method and iron ion reduction antioxidant method(FRAP),the results indicated that the activities and total activity of free and bound antioxidants significantly increased after seed germination.Accordingly,six dayssprouts of tartary buckwheat after seed germination would have a good market prospect.