小麦籽粒不同层次酚类物质与抗氧化活性差异及氮肥调控效应

Distribution of phenolic compounds and antioxidant activities in layered grinding wheat flour and the regulation effect of nitrogen fertilizer application

明确酚类物质在籽粒不同层次的分布规律及对氮肥调控的响应,为小麦品质改良及优质栽培提供科学依据。本研究以紫麦(冀紫439)和白麦(鑫华麦818)为材料,于2019—2020年分别在郑州和原阳设置高氮(HN,210 kg N hm^(-2))和低氮(LN,105 kg N hm^(-2))处理,采用分层碾磨方法将籽粒从外向内依次分为5层(LY1,LY2,LY3,LY4,LY5),测定不同层次籽粒中的总酚、总类黄酮、花青素含量及其抗氧化活性。结果表明,游离酚和结合酚提取物中的总酚、总类黄酮、花青素含量以及抗氧化活性(TEAC、FRAP)从籽粒外层到内层呈下降趋势。紫麦籽粒不同层次抗氧化物含量及抗氧化活性均高于白麦,但两品种之间的差异随着研磨程度的加深呈下降趋势。籽粒LY1~LY3中总酚、总类黄酮和花青素含量随着施氮量的增加而增加(原阳LY1总酚除外),而内层LY4~LY5增对施氮肥的响应较弱,且存在地点间差异。小麦籽粒酚酸组分中阿魏酸占全部组分93%以上,且表现为在低氮条件下含量增高。综上所述,紫麦具有较高的酚类等抗氧化物质,但与白麦之间的差异随着研磨程度的加深而下降;籽粒外层抗氧化物质含量和抗氧化活性对氮肥调控具有较强的响应,且含量随着氮肥增施而增加。

Clarifying the distribution of phenolic compounds in layered grinding wheat flour and its response to nitrogen fertilizer application would provide useful information for wheat quality improvement and high-quality cultivation.Two wheat cultivars,purple wheat(Jizi 439)and white wheat(Xinhuamai 818),were planted with two nitrogen application rate(HN,N 210 kg hm^(-2);LN,N 105 kg hm^(-2))in Zhengzhou and Yuanyang experimental sites during growing period in 2019 and 2020.The mature grains were ground into five milling fractionations(LY1,LY2 LY3,LY4,and LY5)from the bran layer to the endospermic layer by lay-ered grinding,and the total phenolic content(TPC),the total flavonoids content(TFC),and the anthocyanin content(AC),and their antioxidant activity were determined.The results showed that the TPC,TFC,AC,and antioxidant activity(TEAC,FRAP)in free phenols and conjugated phenols extracts decreased from the outer layer flour fractionation to the inner layer flour fractionation.The purple wheat,named as Jizi 439,had a higher antioxidant content and antioxidant activity than white wheat(Xinhuamai 818),but the difference between the two cultivars displayed a decreasing trend from the bran layer flour fractionation to en-dosperm layer flour fractionation.The TPC,TFC,and AC of LY1 to LY3 flour fractionation increased with the increase of nitro-gen fertilizer application except for TPC of LY1 in Yuanyang.However,the contents of total phenolics and total flavonoids of LY4 to LY5 flour fractionation had a weak response to nitrogen fertilizer application.The content of ferulic acid accounted for more than 93%of the TPC in wheat grains and had a higher value under low nitrogen condition.In conclusion,purple wheat had higher antioxidant substances such as phenolics than white wheat,and the difference between purple wheat and white wheat de-creased with the deepening of grinding degree.The content and activity of antioxidants in the outer layer flour fractionation were significantly responsive to nitrogen regulation,and the content increased with the increase of nitrogen.