Optimization for quantification of sorghum tannins by Ferric ammonium citrate assay

Q2 Agricultural and Biological Sciences
Xujuan Wang, Xiaoxian Han, Limin Li, Xueling Zheng
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引用次数: 4

Abstract

Due to the complexity of structure, it is difficult to determine the content of sorghum tannins. The current method for the determination of sorghum tannins is the Ferric ammonium citrate assay described in ISO 9648. However, the standard tannic acid (TA) used in the ISO 9648 method is significantly different in both structure and dynamics from sorghum tannins, resulting in inaccurate quantitative result. Furthermore, the extraction solvent, 75% dimethylformamide (DMF), used in each step of this method had large toxicity to human. Hence, the objective of this study is to optimize the ISO 9648 method by selecting proper standard and extraction solvents so as to enhance the accuracy and safety. In this study, Sephadex LH-20 chromatography combined with high pressure liquid chromatography was used to purify and identify the extracted sorghum tannin (ST). Then, commercial TA, epicatechin (EA), grape seed procyanidin (PA) were selected as the standard and ST was used as reference for Ferric ammonium citrate assay to compare the effects of the three standards. Furthermore, the extraction rates of sorghum tannins in the presence of several low toxic solvents, such as absolute ethanol, absolute methanol, 70% ethanol solution, 70% methanol solution and 70% acetone solution, were compared to determine the alternative solvents of 75% DMF solution. The results showed that PA was superior to TA and EA in structure, with satisfactory color yield close to ST, and higher accuracy than TA. In terms of the extraction solvent, 70% acetone solution was selected to replace 75% DMF solution because of its higher extraction yield (only next to 75% DMF) and low toxicity. Verification experiment results showed that both the recovery rate and the repeatability of the optimized method met the requirements of AOCO. Moreover, the optimized method, with higher accuracy and safety than the ISO 9648 method, can be applied widely in laboratory.

枸橼酸铁铵法测定高粱单宁含量的优化
由于结构的复杂性,高粱单宁含量的测定存在一定的困难。目前测定高粱单宁的方法是ISO 9648中描述的柠檬酸铁铵测定法。然而,ISO 9648方法中使用的标准单宁酸(TA)在结构和动力学上与高粱单宁有显著差异,导致定量结果不准确。此外,该方法每一步所用的提取溶剂75%二甲基甲酰胺(DMF)对人体具有较大的毒性。因此,本研究的目的是通过选择合适的标准品和萃取溶剂来优化ISO 9648方法,以提高其准确性和安全性。本研究采用Sephadex LH-20色谱法结合高压液相色谱法对提取的高粱单宁进行纯化和鉴定。然后以市售TA、表儿茶素(EA)、葡萄籽原花青素(PA)为标准品,以ST为参比品,比较三种标准品测定柠檬酸铁铵的效果。通过比较无水乙醇、无水甲醇、70%乙醇溶液、70%甲醇溶液和70%丙酮溶液等低毒溶剂对高粱单宁的提取率,确定75% DMF溶液的可选溶剂。结果表明,PA在结构上优于TA和EA,显色率接近ST,准确度高于TA。在提取溶剂方面,选择70%丙酮溶液代替75% DMF溶液,因为70%丙酮溶液提取率高(仅次于75% DMF),而且毒性低。验证实验结果表明,优化方法的回收率和重复性均满足AOCO的要求。优化后的方法比ISO 9648方法具有更高的准确度和安全性,可广泛应用于实验室。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
CiteScore
7.30
自引率
0.00%
发文量
69
审稿时长
12 weeks
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