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MALDI-MS of flavonoids: a systematic investigation of ionization and in-source dissociation mechanisms

机译：类黄酮的MALDI-MS：对电离和源内解离机理的系统研究

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Matrix assisted laser desorption ionization (MALDI) is a technique widely employed in the analysis of proteins and peptides, and nowadays it has also been applied to small molecules. There is little significant information regarding the in-source dissociation processes on MALDI for natural products. Twenty-six flavonoids (flavanones, flavones and flavonols) were analyzed by MALDI using different methods (with different matrices) and without matrix to comprehend the in-source reactions and establish good analysis methods for these compounds. Depending on the class, structure and the laser intensity applied, methoxylated flavonoid aglycones can eliminate methyl radicals (CH3) in the source, such as flavonols, but lithium 2,4-dihydroxybenzoate matrix suppresses the CH3 eliminations and retro-Diels-Alder cleavages in the source. All of the flavonoid O-glycosides evaluated herein eliminated the sugar in source, even in the presence of the matrix, and its product radical ions ([M-H-sugar](-)) were observed in the negative mode. The flavone C-glycosides suffered intense dissociation, which was reduced by the addition of a matrix and the application of low laser intensity, mainly in the negative mode. Depending on the hydroxyl substituents, the [M-H-H](-) ion was observed with variable relative intensity in the spectra. Copyright (c) 2015 John Wiley & Sons, Ltd.
机译：基质辅助激光解吸电离（MALDI）是一种广泛用于蛋白质和多肽分析的技术，如今，它也已应用于小分子。关于天然产物的MALDI的源内解离过程，几乎没有重要的信息。使用不同的方法（使用不同的基质）在没有基质的情况下通过MALDI分析了26种黄酮类化合物（黄酮类，黄酮类和黄酮醇类），以了解源头反应并为这些化合物建立良好的分析方法。取决于类别，结构和所施加的激光强度，甲氧基化的类黄酮苷元可以消除源中的甲基自由基（CH3），例如黄酮醇，但是2,4-二羟基苯甲酸锂基质抑制CH3的消除和Diels-Alder逆向裂解。来源。本文评估的所有类黄酮O-糖苷都即使在基质存在下也从源头消除了糖，并且其产物自由基离子（[M-H-糖]（-））以负离子模式观察到。黄酮C-糖苷发生强烈的离解，这主要是通过在负离子模式下通过添加基质和施加较低的激光强度来减少的。取决于羟基取代基，在光谱中以可变的相对强度观察到[M-H-H]（-）离子。版权所有（c）2015 John Wiley＆Sons，Ltd.

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