Stability and Degradation of Caffeoylquinic Acids under Different Storage Conditions Studied by High-Performance Liquid Chromatography with Photo Diode Array Detection and High-Performance Liquid Chromatography with Electrospray Ionization Collision-Induced Dissociation Tandem Mass Spectrometry

Abstract

Caffeoylquinic acids (CQAs) are main constituents in many herbal medicines with various biological and pharmacological effects. However, CQAs will degrade or isomerize when affected by temperature, pH, light, etc. In this study, high-performance liquid chromatography with photodiode array detection (HPLC-PDA) and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was utilized to study the stability and degradation of CQAs (three mono-acyl CQAs and four di-acyl CQAs) under various ordinary storage conditions (involving different temperatures, solvents, and light irradiation). The results indicated that the stability of CQAs was mainly affected by temperature and light irradiation, while solvents did not affect it in any obvious way under the conditions studied. Mono-acyl CQAs were generally much more stable than di-acyl CQAs under the same conditions. Meanwhile, the chemical structures of 30 degradation products were also characterized by HPLC-MS n , inferring that isomerization, methylation, and hydrolysis were three major degradation pathways. The result provides a meaningful clue for the storage conditions of CQAs standard substances and samples.

Recent advances in extraction and analysis procedures of natural chlorogenic acids

“…According to Deshpande et al (2014) under the aqueous basic conditions the intramolecular acyl migration in monoCQAs is fully reversible. Through intramolecular acyl migration in monoCQAs, 5-CQA first isomerizes to 4-CQA (also known as cryptochlorogenic acid), then to 3-CQA (neochlorogenic acid), and finally to 1-CQA (Wianowska et al 2015b;Dawidowicz and Typek 2010;Xue et al 2016). It should be added that among the all 5-CQA isomers the presence of 3-and 4-CQA was confirmed in plants while the 1-CQA isomer is known only from theoretical considerations (Clifford 2000).…”

“…Yet the monoCQAs are generally much more stable than the diCQAs under the same conditions. Taking into account the diCQAs stability, in Xue et al (2016) it was reported that 4,5-diCQa is much more stable than 3,4-diCQA and 3,5-diCQA. Citing the authors of this report, this might be due to the fact that diCQAs are more stable when the ester bond is attached to the quinic acid exists as an equatorial bond rather than the axial one.…”

“…CQAs are highly susceptible to the influence of temperature. As temperature increases they are not only more readily subjected to intramolecular isomerization and transesterification but also to degradation (Farah et al 2005;Jaiswal et al 2012;Wianowska et al 2015a, b;Typek 2010, 2017;Xue et al 2016). The diCQAs degrade to the corresponding monoCQAs and then to caffeic and quinic acids.…”

“…It should be stressed, however, that this evaluation strongly depends on the sensitivity of the applied analytical instrument. According to Xue et al (2016), the total of eight degradation products of 3,4-diCQA, six degradation products of 3,5-diCQA, four degradation products of 1,3-diCQA, and three degradation products of 4,5-diCQA were identified in the diCQAs solutions. In the case of monoCQAs solutions, only two degradation products of 3-CQA, three degradation products of 5-CQA, and four degradation products of 4-CQA were detected and identified (Xue et al 2016).…”

“…According to Xue et al (2016), the total of eight degradation products of 3,4-diCQA, six degradation products of 3,5-diCQA, four degradation products of 1,3-diCQA, and three degradation products of 4,5-diCQA were identified in the diCQAs solutions. In the case of monoCQAs solutions, only two degradation products of 3-CQA, three degradation products of 5-CQA, and four degradation products of 4-CQA were detected and identified (Xue et al 2016). However, as demonstrated in Dawidowicz and Typek (2015), long heating of the 5-CQA solution alone produces at least twenty compounds being 5-CQA derivatives as well as its reaction product with water and methanol.…”