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Colorimetric Sensing of Antioxidant Capacity via Auric Acid Reduction Coupled to ABTS Oxidation
ACS Omega ( IF 3.7 ) Pub Date : 2024-03-03 , DOI: 10.1021/acsomega.3c09134 Burcu Bekdeşer 1 , Reşat Apak 1, 2
ACS Omega ( IF 3.7 ) Pub Date : 2024-03-03 , DOI: 10.1021/acsomega.3c09134 Burcu Bekdeşer 1 , Reşat Apak 1, 2
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In this study, a simple and sensitive colorimetric assay has been developed for total antioxidant capacity measurement. The assay is based on the absorption measurement of the bluish-green oxidized product (ABTS·+) formed as a result of the oxidation reaction of the chromogenic reagent ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) with gold(III). However, in the presence of antioxidants, the ABTS oxidation process is effectively suppressed due to the reduction of gold(III) ions to the zerovalent state forming gold nanoparticles (AuNPs). Relatively lighter colors and a significant decrease in absorbance are observed depending on the total antioxidant capacity. Taking advantage of this situation, qualitative and quantitative total antioxidant capacity (TAC) measurements, with the naked eye and UV–vis spectroscopy, respectively, could be successfully performed. The assay is named “auric reducing antioxidant capacity” (AuRAC) because the gold(III) ion-reducing ability of antioxidants is measured. The AuRAC assay was applied to dietary polyphenols, vitamin C, thiol-type antioxidants, and their synthetic mixtures. Trolox equivalent antioxidant capacity (TEAC) values obtained with the AuRAC assay were found to be compatible with those of the reference CUPRAC (cupric reducing antioxidant capacity) assay. The AuRAC assay was validated through linearity, additivity, precision, and recovery, demonstrating that the assay is reliable and robust. Compared to the simple TAC assays in the literature based on AuNP formation with subsequent surface plasmon resonance (SPR) absorbance measurement, this indirect assay has a smoother linear range starting from lower antioxidant concentrations. This method displays much higher molar absorption coefficients for antioxidant compounds than other conventional single electron transfer (SET) assays because 3-e– reduction of trivalent gold (i.e., Au(III) → Au(0)) produces three chromophore cation radicals (ABTS·+) of the assay reagent. The sensor has been successfully applied to complex matrices, such as tea infusions and pharmaceutical samples. The AuRAC assay stands out with its high molar absorptivity connected to enhanced sensitivity as well as its potential to convert into a paper-based colorimetric sensor.
中文翻译：
通过金酸还原与 ABTS 氧化耦合的抗氧化能力比色传感
在本研究中，开发了一种简单而灵敏的比色测定法，用于测量总抗氧化能力。该测定基于显色试剂 ABTS（2,2'-azinobis(3-乙基苯并噻唑啉-6-磺酸）氧化反应形成的蓝绿色氧化产物 (ABTS ·+ ) 的吸收测量然而，在存在抗氧化剂的情况下，由于金（III）离子还原成零价态，形成相对较浅的金纳米粒子（AuNP），ABTS氧化过程被有效抑制。利用这种情况，可以分别用肉眼和紫外可见光谱成功地进行定性和定量总抗氧化能力（TAC）测量，该测定被命名为“auric”。降低抗氧化能力”（AuRAC），因为 AuRAC 测定法适用于膳食多酚、维生素 C、硫醇型抗氧化剂及其合成混合物。发现通过 AuRAC 测定获得的 Trolox 当量抗氧化能力 (TEAC) 值与参考 CUPRAC（铜降低抗氧化能力）测定的值一致。 AuRAC 测定通过线性、加和性、精密度和回收率进行了验证，证明该测定可靠且稳健。与文献中基于 AuNP 形成和随后的表面等离子共振 (SPR) 吸光度测量的简单 TAC 测定相比，这种间接测定从较低的抗氧化剂浓度开始具有更平滑的线性范围。 该方法显示出比其他传统单电子转移 (SET) 测定法更高的抗氧化化合物摩尔吸收系数，因为 3-e –三价金还原（即 Au(III) → Au(0)）会产生三个发色团阳离子自由基 (ABTS) ·测定试剂的+ )。该传感器已成功应用于复杂基质，例如茶汤和药物样品。 AuRAC 检测以其高摩尔吸收率、增强的灵敏度以及转化为纸基比色传感器的潜力而脱颖而出。
更新日期：2024-03-03
中文翻译：
通过金酸还原与 ABTS 氧化耦合的抗氧化能力比色传感
在本研究中，开发了一种简单而灵敏的比色测定法，用于测量总抗氧化能力。该测定基于显色试剂 ABTS（2,2'-azinobis(3-乙基苯并噻唑啉-6-磺酸）氧化反应形成的蓝绿色氧化产物 (ABTS ·+ ) 的吸收测量然而，在存在抗氧化剂的情况下，由于金（III）离子还原成零价态，形成相对较浅的金纳米粒子（AuNP），ABTS氧化过程被有效抑制。利用这种情况，可以分别用肉眼和紫外可见光谱成功地进行定性和定量总抗氧化能力（TAC）测量，该测定被命名为“auric”。降低抗氧化能力”（AuRAC），因为 AuRAC 测定法适用于膳食多酚、维生素 C、硫醇型抗氧化剂及其合成混合物。发现通过 AuRAC 测定获得的 Trolox 当量抗氧化能力 (TEAC) 值与参考 CUPRAC（铜降低抗氧化能力）测定的值一致。 AuRAC 测定通过线性、加和性、精密度和回收率进行了验证，证明该测定可靠且稳健。与文献中基于 AuNP 形成和随后的表面等离子共振 (SPR) 吸光度测量的简单 TAC 测定相比，这种间接测定从较低的抗氧化剂浓度开始具有更平滑的线性范围。 该方法显示出比其他传统单电子转移 (SET) 测定法更高的抗氧化化合物摩尔吸收系数，因为 3-e –三价金还原（即 Au(III) → Au(0)）会产生三个发色团阳离子自由基 (ABTS) ·测定试剂的+ )。该传感器已成功应用于复杂基质，例如茶汤和药物样品。 AuRAC 检测以其高摩尔吸收率、增强的灵敏度以及转化为纸基比色传感器的潜力而脱颖而出。
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