cynarine is an artifact of extraction procedures derived from the isomerization of 1,5 di-O-caffeoylquinic acid. I would prefer to quantify the precursor content.
First of all thanks for your answer. A few other questions if you can help. 1) You mean, that cynarine cannot be quantified? What method should I use for the extraction of this precursor (e.g. solvent extraction)? 3) Is there any protocol for the analysis of this precursor? Thanks in advance.
you're welcome.
Cynarine may be detected as well as all other caffeoylquinic acids but, from a phytochemical point of view, has no sense to quantify an artifact because this last is not a genuine component of the plant. In addition, it is not possible to quantify the ratio of isomerization of the parent compound. You may refer to this paper but many others are available in literature: http://pubs.acs.org/doi/abs/10.1021/jf062009b (Quantitative Determination of Phenolic Compounds in Artichoke-Based Dietary Supplements and Pharmaceuticals by High-Performance Liquid Chromatography, J. Agric. Food Chem., 2006, 54 (23), pp 8812–8817. DOI: 10.1021/jf062009b ).
Cynarine is mainly reported as artifact derived from water extraction, I suppose by decoction, so temperature could be a cause of isomerization. Also ethanol extraction, as well as all solvents extractions, requires some heating, also on reduced pressure, to eliminate the solvent from the extract, and this step may cause some isomerization. The best solution I suppose could be the cold extraction of the plant juice by mechanic method. Purification of the juice from particulates, large proteins, etc. could be done e.g. by filtration and ultrafiltration (one or more procedures that avoid heating of the sample) so to obtain a sample that could be directly applied on HPLC.
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