Department of Food and Human Nutritional Sciences, University of Manitoba; Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba.
Department of Food and Human Nutritional Sciences, University of Manitoba; Richardson Centre for Functional Foods and Nutraceuticals, University of Manitoba;
J Vis Exp. 2022 Jun 10(184). doi: 10.3791/62467.
Phenolic acids are a class of organic compounds that bear both a phenolic group, and a carboxylic group. They are found in grains and concentrate in the bran of cereals or seed coat of legumes. They possess antioxidant properties that have generated much research interest in recent years, about their potential antioxidant protective health functions. This work presents a generalized method for the extraction of free soluble phenolic acids from whole grains and analysis of their antioxidant capacity. Five whole grain samples comprising two cereals (wheat and yellow corn) and three legumes (cowpea bean, kidney bean, and soybean), were used. The grains were milled into flour and their free soluble phenolic acids extracted using aqueous methanol. The compounds were then identified using a high-pressure liquid chromatograph (HPLC). The Folin-Ciocalteu method was used to determine their total phenolic content while their antioxidant capacities were determined using the DPPH radical scavenging capacity, Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays. The phenolic acids identified included vanillic, caffeic, p-coumaric and ferulic acids. Vanillic acid was identified only in cowpea while caffeic acid was identified only in kidney bean. p-Coumaric acid was identified in yellow corn, cowpea, and soybean, while ferulic acid was identified in all the samples. Ferulic acid was the predominant phenolic acid identified. The total concentration of phenolic acids in the samples decreased in the following order: soybean > cowpea bean > yellow corn = kidney bean > wheat. The total antioxidant capacity (sum of values of DPPH, TEAC and ORAC assays) decreased as follows: soybean > kidney bean > yellow corn = cowpea bean > wheat. This study concluded that HPLC analysis as well as DPPH, TEAC, and ORAC assays provide useful information about the phenolic acid composition and antioxidant properties of whole grains.
酚酸是一类既含有酚基团又含有羧基的有机化合物。它们存在于谷物中，在谷物的麸皮或豆类的种皮中浓缩。近年来，它们具有抗氧化特性，引起了人们的广泛关注，研究其潜在的抗氧化保护健康功能。本工作提出了一种从全谷物中提取游离可溶性酚酸并分析其抗氧化能力的通用方法。使用了五种全谷物样品，包括两种谷物（小麦和黄玉米）和三种豆类（豇豆、芸豆和大豆）。将谷物磨成面粉，然后用甲醇水溶液提取其游离可溶性酚酸。使用高效液相色谱（HPLC）对化合物进行鉴定。使用福林-考尔法测定总酚含量，使用 DPPH 自由基清除能力、Trolox 等效抗氧化能力（TEAC）和氧自由基吸收能力（ORAC）测定其抗氧化能力。鉴定出的酚酸包括香草酸、咖啡酸、对香豆酸和阿魏酸。香草酸仅在豇豆中鉴定出，咖啡酸仅在芸豆中鉴定出。对香豆酸在黄玉米、豇豆和大豆中鉴定出，阿魏酸在所有样品中鉴定出。阿魏酸是鉴定出的主要酚酸。样品中酚酸的总浓度按以下顺序降低：大豆>豇豆>黄玉米=芸豆>小麦。总抗氧化能力（DPPH、TEAC 和 ORAC 测定值之和）按以下顺序降低：大豆>芸豆>黄玉米=豇豆>小麦。本研究得出结论，HPLC 分析以及 DPPH、TEAC 和 ORAC 测定可提供有关全谷物中酚酸组成和抗氧化特性的有用信息。
