低海拔地区黑苦荞酚类物质含量、组成及抗氧化活性研究

为探究黑苦荞的市场利用价值,该研究选择种植于湖北江汉平原低海拔地区的川荞1号和九江苦荞作为材料,分析苦荞籽粒中游离酚、结合酚、总酚、游离黄酮、结合黄酮和总黄酮的含量,利用DPPH自由基法、ABTS自由基法和铁离子还原抗氧化法(FRAP)三种抗氧化测试模型综合评价其体外抗氧化活性,并运用高效液相色谱(HPLC)技术对其酚类物质的组成进行鉴定。结果表明:(1)川荞1号籽粒的总酚和总黄酮含量显著高于九江苦荞,分别为27.38 mg GAE·g~(-1)DW、31.46 mg RE·g~(-1)DW和12.71 mg GAE·g~(-1)DW、14.68 mg RE·g~(-1)DW;其中游离酚与游离黄酮含量显著高于结合酚与结合黄酮含量,均占总酚和总黄酮含量的79%以上,且九江苦荞中结合酚和结合黄酮的含量高于川荞1号。(2)苦荞籽粒中酚类物质主要由芦丁、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-吡喃葡萄糖苷等黄酮类化合物组成,其中游离酚以芦丁和槲皮素为主,结合酚以表儿茶素和芦丁为主。(3)苦荞籽粒提取物均具有一定的抗氧化活性,黑苦荞川荞1号游离态DPPH、ABTS和FRAP抗氧化能力值分别为30.14、11.03、18.84 mg TE·g~(-1)DW,高于九江苦荞,而结合态三种抗氧化能力值低于九江苦荞,但黑苦荞川荞1号总抗氧化能力显著高于九江苦荞。在低海拔地区江汉平原,种植的黑苦荞川荞1号籽粒具有较高含量的酚类物质,符合后续的食品加工的生产要求,市场开发前景广阔。

Contents, compositions and antioxidant activities of phenolic compounds in seeds of black tartary buckwheat planted in low-elevation regions

In order to explore the market value of black tartary buckwheat, we analyzed the phenolics and antioxidant activities of Chuanqiao 1 and Jiujiang Kuqiao, two tartary buckwheat varieties planted in the low-elevation regions of the Jianghan Plain of Hubei, determined the contents of free, bound and total phenolics and flavonoids, and we analyzed the antioxidant activities of their seed extracts in vitro using the DPPH free radical, ABTS free radical and iron ion reduction antioxidant(FRAP)assays, and we also determined the phenolic compositions of the seed extracts by the high performance liquid chromatography(HPLC). The results were as follows:(1)The contents of total phenolics and total flavonoids were significantly higher in the seeds of Chuanqiao 1 than those of Jiujiang Kuqiao, with the former standing at 27.38 mg GAE·g^-1 DW and 31.46 mg RE·g^-1 DW and the latter at 12.71 mg GAE·g^-1 DW and 14.68 mg RE·g^-1 DW; in the seeds of the two varieties, the contents of the free phenolics and flavonoids, which made up more than 79% of the total phenolics and flavonoids, were significantly higher than those of bound phenolics and flavonoids; the contents of bound phenolics and flavonoids were higher in the seeds of Jiujiang Kuqiao than those of Chuanqiao 1.(2)Rutin, quercetin, epicatechin, kaempferol, kaempferol-3-rutinoside and quercetin-3-O-rutinoside-3''-O-glucopyranoside dominated among the phenolic compounds in the seeds of the black tartary buckwheat varieties, with rutin and quercetin dominant phenolics among the free phenolic compounds and epicatechin and rutin dominant among the bound ones.(3)All the seed extracts of the tartary buckwheat varieties presented antioxidant activities and the antioxidant activities of the free seed extracts of Chuanqiao 1, determining as being 30.14, 11.03 and 18.84 mg TE·g^-1 DW using DPPH, ABTS and FRAP, respectively, were higher than those of Jiujiang Kuqiao. The antioxidant activities of the bound extracts of Chuanqiao 1 were lower than those of Jiujiang Kuqiao, but the total antioxidant acti-vity of the former variety was significantly higher than that of the latter one. Therefore, planted in low-elevation regions of the Jianghan Plain, Chuanqiao 1 had higher contents of seed phenolic compounds, as being required in subsequent food processing and presenting a bright market prospect.