Phenolic compounds are secondary metabolites generally involved in plant adaptation to environmental stress conditions. Chlorogenic acids (CGA) and related compounds are the main components of the phenolic fraction of green coffee beans, reaching levels up to 14 % (dry matter basis). These compounds have a number of beneficial health properties related to their potent antioxidant activity as well as hepatoprotective, hypoglycemic and antiviral activities. The main groups of CGA found in green coffee beans include caffeoylquinic acids, dicaffeoylquinic acids, feruloylquinic acids, p-coumaroylquinic acids and mixed diesters of caffeic and ferulic acids with quinic acid, each group with at least three isomers. During coffee processing, CGA may be isomerized, hydrolyzed or degraded into low molecular weight compounds. The high temperatures of roasting also produce transformation of part of CGA into quinolactones and, along with other compounds, melanoidins. This review focuses on the chemical characteristics, biosynthesis, and distribution of CGA and related compounds in coffee. The influence of genetic, physiological and environmental factors as well as processing on the chemical composition of coffee beans is discussed. The impact of CGA composition of green coffee on cup quality is also approached. Despite the existence of substantial published information on the total levels of CGA in coffee, more research is needed on the composition of minor phenolic compounds and specific CGA isomers (and related substances) in green and roasted coffee beans, as well as their impact on coffee quality. Key words: Coffea, chlorogenic acids, chlorogenic acid lactones, coffee quality, coffee processing, coffee roasting, quinides. Compostos fenólicos em café:Os compostos fenólicos são metabólitos secundários de plantas envolvidos na adaptação a condições de estresse ambiental. Os ácidos clorogênicos (CGA) e compostos relacionados são os principais componentes da fração fenólica dos grãos de café verde, alcançando teores de até 14 % (em peso seco). Estes compostos apresentam propriedades benéficas à saúde, não só devido à sua potente atividade antioxidante, mas também como agentes hepatoprotetores, hipoglicemiantes, e antivirais. Os principais grupos de CGA encontrados nos grãos de café verde incluem os ácidos cafeoilquínicos, dicafeoilquínicos, feruloilquínicos, p-cumaroilquínicos e ésteres mixtos dos ácidos cafeico e ferúlico com ácido quínico, com pelo menos três isômeros por grupo. Durante o processamento do café, os CGA podem ser parcialmente isomerizados, hidrolizados ou degradados a compostos de baixo peso molecular. As altas temperaturas observadas no processo de torrefação produzem também a formação de lactonas e a polimerização dos CGA com outros componentes do café para formar melanoidinas. Esta revisão aborda as características químicas, a biosíntese e a distribuição dos CGA e compostos relacionados nos grãos de café. A influência de fatores que modificam a composição dos grãos verdes, tais como genéticos, fisiológicos ...

Chlorogenic acids (CGA) are cinnamic acid derivatives with biological effects mostly related to their antioxidant and antiinflammatory activities. Caffeoylquinic acids (CQA) and dicaffeoylquinic acids (diCQA) are the main CGA found in nature. Because green coffee is a major source of CGA, it has been used for production of nutraceuticals. However, data on the bioavailability of CGA from green coffee in humans are inexistent. The present study evaluated the pharmacokinetic profile and apparent bioavailability of CGA in plasma and urine of 10 healthy adults for 8 h after the consumption of a decaffeinated green coffee extract containing 170 mg of CGA. Three CQA, 3 diCQA, and caffeic, ferulic, isoferulic, and p-coumaric acids were identified in plasma by HPLC-Diode Array Detector-MS after treatment. Over 30% (33.1 +/- 23.1%) of the ingested cinnamic acid moieties were recovered in plasma, including metabolites, with peak levels from 0.5 to 8 h after treatment. CGA and metabolites identified in urine after treatment were 4-CQA, 5-CQA, and sinapic, p-hydroxybenzoic, gallic, vanillic, dihydrocaffeic, caffeic, ferulic, isoferulic, and p-coumaric acids, totaling 5.5 +/- 10.6% urinary recovery of the ingested cinnamic and quinic acid moiteties. This study shows that the major CGA compounds present in green coffee are highly absorbed and metabolized in humans.

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.

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In the present study, the influence of coffee roasting on free and melanoidin-bound phenolic compounds and their relationship with the brews' antioxidant activity (AA), evaluated by TRAP, TEAC, and TRAP, were investigated. Changes in the relative content of free chlorogenic acids (CGA), free lactones, and melanoidin-bound phenolic acids during roasting indicate that phenolic compounds were incorporated into melanoidins mainly at early stages of the process, being thereafter partly oxidized to dihydrocaffeic acid, and degraded. Although less than 1% of CGA in green coffee was incorporated into melanoidins during roasting, the relative content of melanoidin-bound phenolic acids increased significantly during this process, reaching up to 29% of total phenolic compounds in brews from dark roasted coffees. Regardless of the AA assay used and considering all roasting degrees, the overall contribution of CGA to the AA of the whole brews was higher than that of melanoidin-bound phenolic compounds. It was estimated that the latter compounds contributed to 25-47% of the AA, depending on the assay used.