大麦发芽过程中不同存在形式的酚类物质及其抗氧化活性变化

以甘啤4号为原料,研究发芽过程中4类多酚物质提取物的含量及其抗氧化活性的变化,采用的评价指标为DPPH自由基清除活性、ABTS自由基清除活性和铁还原力,同时利用HPLC法依次检测4类粗多酚中9种单体酚酸的含量及其变化。试验结果表明:发芽显著影响大麦粗多酚、单体酚酸的种类和含量及其抗氧化活性。游离粗多酚在原麦和萌发过程中始终占总粗多酚含量的最大比例,并且其综合抗氧化活力也显著高于其它3类粗多酚提取物。4类粗多酚提取物和各单体酚酸的总含量及抗氧活性总是原麦高于各萌发时期,在浸泡阶段统一显著下降,萌发后期又有显著升高。相关性分析表明,4类粗多酚的铁还原能力、清除DPPH和ABTS自由基的能力均与其含量密切相关,与粗多酚显著相关的单体酚酸,同样显著影响着其抗氧化活性。阿魏酸、儿茶素、对香豆酸是主要的活性酚酸。

Variations in the Antioxidant Activities of Four Crude Polyphenolic Extracts from Barley during the Germination Process

The content of four kinds of polyphenolic extract and the variations in their antioxidant activities during germination were investigated in Ganbei 4 barley. The antioxidant activity was evaluated based on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, and ferric reducing activity. Simultaneously, the contents of monomeric phenolic acids from the crude polyphenolic extracts (four types) were determined by high-performance liquid chromatography (HPLC). The results of these analyses revealed the significant influence of malting on the content and types of crude polyphenolic extracts and monomeric phenolic acid, as well as on their antioxidant activities. The proportion of free phenolic acids was observed to be the highest in raw barley than that in germination process.. These values showed a significant decrease during the steeping process; subsequently, the values showed a remarkable increase during the late stage of germination. Correlation analysis revealed a close relation between the ferric-reducing ability, DPPH and ABTS radical scavenging abilities of the four crude polyphenols and their compositions. Monomeric phenolic acids, which were closely related to crude polyphenols, were also observed to significantly affect the antioxidant activities of crude polyphenols. Ferulic acid, catechin, and p-coumaric acid were identified as the major active phenolic acid components of Ganbei 4 barley.