Chlorogenic acid, in coffee

Clifford M.N. (1985a) Chlorogenic acids. In Coffee, Chemistry R.J. Clarke and R. Macrae Eds, Elsevier Applied Science, 153-202. 

Humphrey, C.J. and Macrae, R. (1987) Determination of chlorogenic acid in coffee. Presentation at the 12th International Colloquium on Coffee, Montreux, Switzerland. 

C.). Humphrey and R. Macrae, Determination of Chlorogenic Acid in Coffee , presentation at the 12 International Colloquium on Coffee, Montreux 1987. 

Quinic acid (XIV) is found in cinchona bark, meadow hay, and other plants, and combined with caffeic acid as chlorogenic acid in coffee and other plants. Its total synthesis has been accomplished. 

Clifford MN, Knight S, Surucu B and Kuhnert N. 2006a. Characterization by LC-MS(n) of four new classes of chlorogenic acids in green coffee beans dimethoxycinnamoylquinic acids, diferuloylquinic acids, caffeoyl-dimethoxycinnamoylquinic acids, and feruloyl-dimethoxycinnamoylquinic acids. J Agric Food Chem 54(6) 1957-1969. 

O-Dicaffeoylquinic acid Figure 1.32 Main chlorogenic acids in green coffee beans. 

As an example, Urakova et al. compared the analysis of chlorogenic acid in green coffee bean extracts by thin layer chromatography on silica (i.e. normal-phase liquid chromatography) and by reversed-phase HPLC The validation data (LOD, LOQ, repeatability, and various precision parameters), the recoveries and the quantitative results were totally comparable. It can be assumed that both methods find the true value. Either method can be used, depending on the preference or instrumentation of a laboratory. 

Coffee has been reported to inhibit LDL oxidation in vitro. One class of phenolic substances, the hydroxycinnamic acids, is ubiquitous in its occurrence the most common member of this class is chlorogenic acid, which has been shown to inhibit the oxidative modification of LDL in vitro [49]. Coffee, along with apples and berries, is a major source of chlorogenic acid in the human diet. 

Caffeine is found in a number of botanically unrelated species, including Coffea arabica (Rubiaceae), Camellia sinensis (Theaceae), or tea. Cola nitida (Sterculaciaceae), or kola nut, and Paullinia cupana (Sapindaceae), or guarana. Caffeine is bound to chlorogenic acid in raw coffee beans, the roasting process liberating the caffeine and other compounds that contribute to the aroma of coffee (Samuelsson 1992). 

Bl-Hamidi and Wanner (1964) reported on the occurrence of caffeine and chlorogenic acid in the coffee plant and found that the variable quantitative relation existed during the development of the leaves and fruit. It led the authors to propose in view of this evidence we consider it improbable that the complex could act as a metabolic link between caffeine and chlorogenic acid. It is possible that the complex is formed in vitro by chemical-physical interaction of chlorogenic acid and caffeine. The metabolic link could then serve as a sink or a trap for the caffeine (in the vacuole ). The concentrations of the two substances were not found to change together, and they clearly have different metabolic pathways. 

Ye et al. have determined catechin, rutin, ferulic acid, o-dihydroxybenzene, chlorogenic acid, caffeic acid, gallic acid, and protocatechuic acid in coffee by CE-AD [24]. The working electrode was a carbon disk electrode at an applied potential of -1-0.95 V (vs. SCE). Under the optimum conditions, the analytes can be well separated within 26 min in a 75-cm-long fused-silica capillary. The current response was linear over three orders of magnitude with detection limits ranging from 60 to 360ng/ml for all analytes. 

Caffeine forms, in part, a hydrophobic ti-complex with chlorogenic acid in a molar ratio of 1 1. In a coffee drink, 10% of the caffeine and about 6% of the chlorogenic acid present occur in this form. The caffeine level in beans is only slightly decreased during roasting. Caffeine obtained by the decaffeination process and s)uithetic caffeine are used by the pharmaceutical and soft drink industries. Synthetic caffeine is obtained by methyla-tion of xanthine which is synthesized from uric acid and formamide. 

Chfford M.N., Marks S., Knight S., Kuhnert N. Characterization by LC-MSn of four new classes of p-coumaric acid-containing diacyl chlorogenic acids in green coffee beans. Journal of Agricultural and Food Chemistry, 54 4095-4101 (2006). 

---