Background: Chlorogenic acids (CGAs) are a class of phytochemicals that are formed as esters between different derivatives of cinnamic acid and quinic acid molecules. In plants, accumulation of these compounds has been linked to several physiological responses against various stress factors; however, biochemical synthesis differs from one plant to another. Although structurally simple, the analysis of CGA molecules with modern analytical platforms poses an analytical challenge. The objective of the study was to perform a comparison of the CGA profiles and related derivatives from differentiated tobacco leaf tissues and undifferentiated cell suspension cultures. Results: Using an UHPLC-Q-TOF-MS/MS fingerprinting method based on the in-source collision induced dissociation (ISCID) approach, a total of 19 different metabolites with a cinnamic acid core moiety were identified. These metabolites were either present in both leaf tissue and cell suspension samples or in only one of the two plant systems. Profile differences point to underlying biochemical similarities or differences thereof. Conclusion: Using this method, the regio- and geometric-isomer profiles of chlorogenic acids of the two tissue types of Nicotiana tabacum were achieved. The method was also shown to be applicable for the detection of other related molecules containing a cinnamic acid core.

Extraction is a vital prerequisite in most scientific studies involving the isolation and analysis of compounds from biological/environmental systems. The use of large quantities of organic solvents in performing both conventional and modern methods of extraction of these substances stirs issues of safety, environmental concern and cost-effectiveness. Subcritical water extraction (SWE) offers a suitable, safe, cost-effective and environmentally safe alternative compared to other methods as it takes advantage of the special properties of supercritical water under high temperature and pressure conditions (100–374 °C, >50 bar) to extract non-polar analytes. This review presents a critical appraisal of the principles and dynamics of SWE, and the current applications as a viable tool in the extraction of compounds from various biological matrices. Although more research is needed to improve full SWE applications, its adoption in the extraction of phytochemicals as well as other bioactive molecules including mycotoxins from both plant and animal components seems promising and needs to be properly exploited.

Plants contain a myriad of metabolites which exhibit diverse biological activities. However, in-depth analyses of these natural products with current analytical platforms remains an undisputed challenge due to the multidimensional chemo-diversity of these molecules, amplified by both isomerization and conjugation. In this study, we looked at molecules such as hydroxyl-cinnamic acids (HCAs), which are known to exist as positional and geometrical isomers conjugated to different organic acids namely quinic- and isocitric acid. The study aimed at providing a more defined distinction between HCA conjugates from Amaranthus viridis and Moringa oleifera, using mass spectrometry (MS) approaches. Here, we used a UHPLC–MS/MS targeted approach to analyze isobaric HCA conjugates extracted from the aforementioned plants. Mass spectrometry results showed similar precursor ions and fragmentation pattern; however, distinct differences were seen with ions at m/z 155 and m/z 111 which are associated with isocitric acid conjugates. Our results highlight subtle differences between these two classes of compounds based on the MS fingerprints, enabling confidence differentiation of the compounds. Thus, these findings provide a template reference for accurate and confident annotation of such compounds in other plants.

Chlorogenic acids (CGA) have been profiled in the leaves ofMomordica balsamina,Momordica charantia, andMomordica foetida. All three species were found to contain thetransandcisisomers of 4-acylpara-coumaroylquinic acid (pCoQA), caffeoylquinic acid (CQA), and feruloylquinic acid (FQA). To the best of our knowledge, this is the first report ofpCoQA and FQA and theircisisomers in theseMomordicaspecies. These profiles were obtained by a newly developed UPLC-qTOF-MS method based on the in-source collision induced dissociation (ISCID) method optimized to mimic the MS²and MS³fragmentation of an ion trap-based MS. The presence of thecisisomers is believed to be due to high UV exposure of these plants. Furthermore, the absence of the 3-acyl and 5-acyl CGA molecules points to a metabolic mark that is unusual and represents a very interesting biochemical phenotype of these species. Our optimized ISCID method was also shown to be able to distinguish between the geometrical isomers of all three forms of CGA, a phenomenon previously deemed impossible with other common mass spectrometry systems used for CGA analyses.