Chlorogenic acids chemical structure

Figure 2.3 Example of chemical structure of a chlorogenic acid 5-O-caffeoylquinic acid (with ITJPAC numbering).

Each patent has somewhat different features and claims. We select one patent for more detailed discussion to highlight certain technical facets of the process. First we explain the (often misunderstood) effect of water on the extractability of caffeine by selective supercritical carbon dioxide. A number of references report that dry carbon dioxide cannot extract caffeine from dry coffee, either green or roasted, but moist carbon dioxide can. The inability of dry carbon dioxide to extract caffeine from coffee should not be misconstrued to mean that dry carbon dioxide cannot dissolve neat caffeine. This same moist-versus-dry effect is experienced if, for example, methylene chloride is used to extract caffeine from coffee. Dry methylene chloride cannot decaffein-ate dry coffee but moistened coffee can be decaffeinated. It is thought that the caffeine is chemically bound in a chlorogenic acid structure present in the coffee bean. Thus, water somehow acts as a chemical agent it frees caffeine from its bound form in the coffee matrix in both the carbon dioxide and the methylene chloride processes. 

Figure 2 Chemical structures of selected plant polyphenols. Structures include a flavonol (quercetin), isoflavone (daidzein), cinnamic acid (chlorogenic acid), flavan-3-ol (catechin), a lignan microbial metabolite (enterodiol), and a stilbene (resveratrol).

FIGURE 8.3 Chemical structures of chlorogenic, cryptochlorogenic, and neochlorogenic acids. 

In the case Wh (wool hydrolysate) a small increase of convention potential fiom Tyr to DOPA occurred and readied the maximum after 3 hours of incubation. The difference is a consequence of the substrate structure and the accessibility of the wool tyrosine residues to enzyme. The use of smaller substrates which are chemically similar to DOPA results in a strong decrease of DOPA conversion during the first 2 hours in the case of Wh and caffeic acid. Similarly, the conversion optimum is reached after 4 hours of incubation in the case of Wh and chlorogenic acid combination. The decrease of DOPA after longer incubation time is the consequence of the further oxidation of DOPA to DQ (Figure 3). 

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