Of all plant constituents, coffee has one of the highest concentrations of chlorogenic acids. When roasting coffee, some of these are transformed into chlorogenic acid lactones (CGL). We have studied the formation of CGL during the roasting of coffee beans in Coffea arabica cv. Bourbon; C. arabicacv. Longberry; and C. canephora cv. Robusta. Individual CGL levels were determined by comparison of HPLC peaks with those of synthetic CGL standards. Seven CGL were identified: 3-caffeoylquinic-1,5-lactone (3-CQL), 4- caffeoylquinic-1,5-lactone (4-CQL), 3-coumaroylquinic-1,5-lactone (3-pCoQL), 4-coumaroylquinic-1,5-lactone (4-pCoQL), 3-feruloylquinic-1,5-lactone (3-FQL), 4-feruloylquinic-1,5-lactone (4-FQL), and 3,4-dicaffeoylquinic-1,5-lactone (3,4-diCQL). 3-CQL was the most abundant lactone in C. arabica and C. canephora, reaching peak values of 230 +/- 9 and 254 +/- 4 mg/100 g (dry weight), respectively, at light medium roast ( approximately 14% weight loss). 4-CQL was the second most abundant lactone (116 +/- 3 and 139 +/- 2 mg/100 g, respectively. The maximum amount of CGL represents approximately 30% of the available precursors. The relative levels of 3-CQL and 4-CQL in roasted coffee were reverse to those of their precursors in green coffee. This suggests that roasting causes isomerization of chlorogenic acids prior to the formation of lactones and that the levels of lactones in roasted coffee do not reflect the levels of precursors in green coffee.

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Chlorogenic acids (CGA) are abundant phenolic compounds in coffee, with caffeoylquinic (CQA), feruloylquinic (FQA), and dicaffeoylquinic (diCQA) acids being the major subclasses. Despite the potential biopharmacological properties attributed to these compounds, little is known about their bioavailability in humans. In this study, we evaluated the distribution profile of the major CGA isomers and metabolites in plasma and urine of 6 healthy adults for 4 h after brewed coffee consumption. Three CQA isomers and 3 diCQA isomers were identified in the plasma of all subjects after coffee consumption, whereas 2 FQA were identified in only 1 subject. Two plasma concentration peaks were observed, the first at 0.5-1.0 h and the second at 1.5-4.0 h after coffee consumption. The molar ratio CQA:diCQA was 12.2 in the brewed coffee, whereas in plasma it ranged from 0.6-2.9. The molar ratios 5-CQA:3-CQA and 5-CQA:4-CQA were consistently higher in plasma than in the brew. The main CGA metabolites identified in urine after coffee consumption were: dihydrocaffeic, gallic, isoferulic, ferulic, vanillic, caffeic, 5-CQA, sinapic, rho-hydroxybenzoic, and rho-coumaric acids (gallic and dihydrocaffeic acids being the major ones). This study indicates that the major CGA compounds present in coffee are differentially absorbed and/or metabolized in humans, with a large inter-individual variation. Moreover, urine does not appear to be a major excretion pathway of intact CGA compounds in humans.

The market for decaffeinated coffees has been increasingly expanding over the years. Caffeine extraction may result in losses of other compounds such as chlorogenic acids (CGA) and, consequently, their 1,5-gamma-quinolactones (CGL) in roasted coffee. These phenolic compounds are important for flavor formation as well as the health effects of coffee; therefore, losses due to decaffeination need to be investigated. The present study evaluates the impact of decaffeination processing on CGA and CGL levels of green and roasted arabica coffees. Decaffeination produced a 16% average increase in the levels of total CGA in green coffee (dry matter), along with a 237% increase in CGL direct precursors. Different degrees of roasting showed average increments of 5.5-18% in CGL levels of decaffeinated coffee, compared to regular, a change more consistent with observed levels of total CGA than with those of CGL direct precursors in green samples. On the other hand, CGA levels in roasted coffee were 3-9% lower in decaffeinated coffee compared to regular coffee. Although differences in CGA and CGL contents of regular and decaffeinated roasted coffees appear to be relatively small, they may be enough to affect flavor characteristics as well as the biopharmacological properties of the final beverage, suggesting the need for further study.

A method, based on high-performance liquid chromatography, is described for the determination of chlorogenic acid isomers in instant coffee. Identification of the individual components was assisted by the preparation of isomeric mixtures by the isomerisation of available compounds and quantification based on published ultraviolet molar absorptivities. A number of extraction and clearing techniques were studied to determine the optimum conditions for the recovery of all the isomers present. The developed method was applied to a wide range of commercially available instant coffees.

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