Abstract
When dealing with simple phenols such as caffeic acid (CA) and ferulic acid (FA), found in a variety of plants, it is very important to have control over the most important factors that accelerate their degradation reactions. This is the first report in which the stabilities of these two compounds have been systematically tested by exposure to various different factors. Forced degradation studies were performed on pure standards (trans-CA and trans-FA), dissolved in different solvents and exposed to different oxidative, photolytic and thermal stress conditions. Additionally, a rapid, sensitive, and selective stability-indicating gas chromatographic-mass spectrometric method was developed and validated for determination of trans-CA and trans-FA in the presence of their degradation products. Cis-CA and cis-FA were confirmed as the only degradation products in all the experiments performed. All the compounds were perfectly separated by gas chromatography (GC) and identified using mass spectrometry (MS), a method that additionally elucidated their structures. In general, more protic solvents, higher temperatures, UV radiation and longer storage times led to more significant degradation (isomerization) of both trans-isomers. The most progressive isomerization of both compounds (up to 43%) was observed when the polar solutions were exposed to daylight at room temperature for 1 month. The method was validated for linearity, precision as repeatability, limit of detection (LOD) and limit of quantitation (LOQ). The method was confirmed as linear over tested concentration ranges from 1−100 mg L−1 (r2s were above 0.999). The LOD and LOQ for trans-FA were 0.15 mg L−1 and 0.50 mg L−1, respectively. The LOD and LOQ for trans-CA were 0.23 mg L−1 and 0.77 mg L−1, respectively.
Highlights
Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova Ulica 17, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna Pot 113, SI-1000 Ljubljana, Slovenia
Despite the abundance of articles related to phenolics, only a few phenolics, only a few of them mention their instability during extraction or analytical of them mention their instability during extraction or analytical procedures [3,4,5,6,7,8,9,10,11]
Phenolic acids (PAs) are present mainly as trans-isomers, but their degradation can occur under various stress conditions
Summary
Faculty of Chemistry and Chemical Engineering, University of Maribor, Smetanova Ulica 17, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna Pot 113, SI-1000 Ljubljana, Slovenia. When dealing with simple phenols such as caffeic acid (CA) and ferulic acid (FA), found in a variety of plants, it is very important to have control over the most important factors that accelerate their degradation reactions This is the first report in which the stabilities of these two compounds have been systematically tested by exposure to various different factors. When working with compounds that are prone to isomerization, decomposition, or the formation of racemic mixtures, they should be handled with care and strict precautions should be taken with respect to illumination, the use of protic organic solvents, elevated temperatures, and long-term analysis in order published maps and institutional affiliations. Molecules 2021, 26, 2475 taken with respect to illumination, the use of protic organic solvents, elevated temperatures, and long-term analysis in order to minimize their to minimize their isomerization/decomposition. Despite the abundance of articles related to phenolics, only a few phenolics, only a few of them mention their instability during extraction or analytical of them mention their instability during extraction or analytical procedures [3,4,5,6,7,8,9,10,11]
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