Phenolic compounds in coffee. Braz

Abstract

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.

Full text

Braz. J. Plant Physiol., 18(1):_-__, 2006
M I N I R E V I E W
Phenolic compounds in coffee1
Adriana Farah and Carmen Marino Donangelo*
Laboratório de Bioquímica Nutricional e de Alimentos. Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio
de Janeiro, Cidade Universitária, CT, Bloco A, Sala 528-A. Ilha do Fundão, Rio de Janeiro, RJ, 21949-900, Brazil. *Corresponding author:
donangel@iq.ufrj.br
Phenolic compounds are secondary plant 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 benecial 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 acid 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 inuence 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
specic 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 benécas 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 de ácido 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 inuência de fatores que modicam a composição dos grãos verdes, tais como genéticos,
siológicos e ambientais, assim como o efeito do processamento sobre a composição de CGA do café são discutidos. O impacto
dos CGA e compostos derivados sobre a qualidade da bebida do café é outro tópico abordado nesta revisão. Apesar da riqueza
de informações na literatura relacionadas aos teores totais de fenólicos e CGA em café, mais investigações são necessárias no
que diz respeito tanto à composição de isômeros especícos dos CGA, de seus derivados, e de outros compostos fenólicos
minoritários presentes no café, quanto ao seu impacto sobre a qualidade da bebida.
Palavras-chave: Coffea, ácidos clorogênicos, ácidos clorogênicos-lactonas, procesamento do café, qualidade do café, torração
do café, quinideos.
1 This work is dedicated to the memory of our dear friend and mentor Prof. Dr Luiz Carlos Trugo for his outstanding contribution to coffee research and for
guiding us into this exciting research eld.
___________

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3
INTRODUCTION
Phenolic compounds are ubiquitous constituents of
higher plants found in a wide range of commonly consumed
plant foods such as fruits, vegetables, cereals and legumes,
and in beverages of plant origin, such as wine, tea and coffee
(Cheynier, 2005; Manach et al., 2004). These compounds
are secondary metabolites of plants generally involved
in defense against ultraviolet radiation or aggression by
pathogens. Several thousands of phenolic compounds
have been described in plant foods and can be grouped
into different classes according to their basic chemical
structure (such as type and number of phenol rings), and
into different subclasses, according to specic substitutions
in the basic structure, association with carbohydrates and
polymerized forms (table 1) (Manach et al., 2004). Most
of these compounds have received considerable attention
as potentially protective factors against human chronic
degenerative diseases (cataracts, macular degeneration,
neurodegenerative diseases, and diabetes mellitus), cancer
and cardiovascular disease (Scalbert et al., 2005).
While condensed tannins are the main phenolic
compounds in coffee pulp, in the seed, phenolic compounds
are present predominantly as a family of esters formed
between certain hydroxycinnamic acids and quinic acid,
collectively known as chlorogenic acids (CGA) (Clifford,
1985a). Other phenolic compounds, such as tannins,
lignans and anthocyanins are also present in coffee seeds
although in minor amounts. CGA, which are present in high
concentrations in green coffee seeds (up to 14 %), have a
marked inuence in determining coffee quality and play
an important role in the formation of coffee avor (Carelli
et al., 1974; Clifford and Wight, 1976; Trugo and Macrae,
1984a, Variyar et al., 2003, Farah, 2006a). Moreover,
these compounds have several benecial health properties
largely explained by their potent antioxidant activity. In
addition, they have exhibited hypoglycemic, antiviral,
hepatoprotective and antispasmodic activities (Basnet et
al., 1996; Trute et al., 1997; Trugo, 2001; Grace et al., 1998;
Natella et al., 2002; Pereira et al., 2003, Moreira et al., 2005).
Their 1,5-γ-quinolactones have also been studied not only
for their potential hypoglycemic effects but for their action
in the brain function, more specically, at the mu opioid and
adenosine receptors (Farah et al., 2005a).
This review focuses on the chemical characteristics, bio-
synthesis, and composition of CGA and related compounds
in coffee, with emphasis on the inuence of genetic, physi-
ological and environmental factors, as well as processing, on
the CGA composition of green coffee beans. The impact of
CGA composition on coffee cup quality is also discussed.
Phenolic composition of coffee fruit
Coffee pulp and skin: In recent years, the number of
studies on the chemical composition of coffee skin and
pulp has been increasing due to their potential use in animal
feeding, especially in coffee producer countries, where
the disposal of wastes represents an important pollution
problem. (Ulloa Rojas et al., 2002; Barcelos et al., 2002).
Tannins, which are the main phenolic compounds in these
parts of the coffee fruit, have received a special attention
because they are considered as anti-nutrients for ruminants
(Barcelos et al., 2001; Barcelos, 2002; Ulloa Rojas et al.,
2002, 2003). Soluble tannins may account for 0.8%-2.8%
of C. arabica and C. canephora skin and pulp, with higher
contents observed in C. canephora, and with prodelphinidins
exceeding procyanidins (Clifford and Ramirez-Martinez,
1991a; Barcelos et al., 2001; Ulloa Rojas et al., 2003). Small
amounts of insoluble condensed tannins may be also found
in the pulp (Clifford and Ramirez-Martinez, 1991a). Soaking
the pulp in water, treatment with alkali solutions, ensilation
with molasses, and inoculation with selected microorganisms
Table 1. Main classes of phenolic compounds in higher
plants.
Classes and sub-classes Examples of specic compounds
Non-avonoid compounds
Phenolic acids
Benzoic acids
Hydroxycinnamic acids
Gallic acid; protocatechuic acid;
p-hydroybenzoic acid
Coumaric acid; caffeic acid;
ferulic acid; sinapic acid
Hydrolyzable tannins Pentagalloylglucose
Stilbenes Resveratrol
Lignans Secoisolariciresinol, matairesinol,
lariciresinol , pinoresinol
Flavonoid compounds
Flavonols Kaempferol; quercitin; myricetin
Flavones Apigenin; luteolin
Flavanones Naringenin; hesperetin
Flavanols Catechins; gallocatechins
Anthocyanidins Pelargonidin; Cyanidin; malvidin
Condensed tannins or
proanthocyanidins
Trimeric procyanidin,
prodelphinidins
Isoavones Daidzein; genistein; glycitein

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3
may destroy or reduce the content of tannins (Ulloa Rojas et
al., 2002; 2003). Storage of dehydrated arabica coffee skin
and pulp also produced a linear decrease in tannins content
(~ 39%/year) (Barcelos et al., 2001).
Smaller amounts of the main groups of CGA found in
coffee beans (caffeoylquinic acids, feruloylquinic acids and
dicaffeoylquinic acids were identied in the pulp (Clifford
and Ramirez-Martinez, 1991b). Grifn and Stonier (1975,
cited by Clifford, 1985) have reported that coffee pulp
contains CGA-protein complexes that are able to inhibit
the enzyme indole acetic acid oxidase. Anthocyanins are
commonly found in skin material of red fruit cultivars
(Mazza and Miniati, 1993).
Coffee beans: CGA have been studied for more than a
century as the main components of the phenolic fraction
of green coffee beans (Clifford, 1979; Trugo, 1984). CGA
include different groups of compounds and related isomers
formed by esterication of one molecule of quinic acid
and one to three molecules of a specic trans-hydroxy-
cinnamic acid (gure 1). Using the preferred IUPAC
numbering system (Clifford, 1985a; 2000), quinic acid (1L-
1(OH),3,4/5-tetrahydroxy-cyclohexane carboxylic acid) has
axial hydroxyl groups on carbons 1 and 3, and equatorial
hydroxyls on carbons 4 and 5. Esters of this acid are usually
formed on carbon 5, but also on carbons 3 and 4, and less
commonly on carbon 1. Hydroxy-cinnamic acids are trans-
Figure 1. Chlorogenic acids and related compounds according to chemical characteristics. (A) Basic compounds; (B) monoesters
of quinic acid with hydroxy-cinnamic acids (example of 5-isomers); (C) di-esters of quinic acid with caffeic acid, and (D)
mixed esters

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phenyl-3-propenoic acids with different substitutions in the
aromatic ring; the most common in coffee is caffeic acid
(3,4-dihydroxy-cinnamic acid) followed by ferulic acid (3-
metoxy, 4-hydroxy- cinnamic acid) and p-coumaric acid (4-
hydroxy- cinnamic acid) (Clifford, 2003).
The main groups of CGA found in green coffee beans
are presented in gure 1, according to their chemical identity,
number and position of acyl residues. These groups of
compounds include: caffeoylquinic acids (CQA), with 3
isomers (3-, 4- and 5-CQA); dicaffeoylquinic acids (diCQA),
with 3 isomers (3,4-diCQA; 3,5-diCQA; 4,5-diCQA);
feruloylquinic acids (FQA), with 3 isomers (3-, 4- and 5-
FQA); p-coumaroylquinic acids (pCoQA), with 3 isomers
(3-, 4- and 5- pCoQA), and six mixed diesters of caffeoyl-
feruloyl-quinic acids (CFAQ) (Clifford, 2003).
Despite the large distribution of some CGA in the plant
kingdom, green coffee is known as one of the main food
sources of CGA, with contents being equaled or exceeded
only by the green leaves of Illex paraguayensis (Maté)
(Clifford and Ramirez-Martinez, 1990; Mazzafera, 1997;
Clifford, 1997; Clifford, 1999). Total CGA content of
green coffee beans may vary according to genetics - species
and cultivar, degree of maturation and, less importantly,
agricultural practices, climate and soil (Clifford, 1985,
Guerrero et al., 2001; Camacho-Cristóbal et al., 2002, Farah
et al., 2005b). The diversity of methodology employed in the
analysis of CGA is another important factor in establishing
levels, since there may be a certain discrepancy between
results obtained by high resolution chromatographic methods
and those obtained by less sophisticated methods.
In general, the values described in the literature for total
CGA in regular green coffee beans, on dry matter basis (dm),
may vary from 4 to 8.4 % for Coffea arabica, and from 7 to
14.4 % for Coffea canephora, with some hybrids presenting
intermediate levels (Ferreira et al., 1971; Rof et al., 1971;
Chassevent et al., 1973; Clifford and Wight, 1976; Rees and
Theaker, 1977; Van der Stegen and Van Duijn, 1980; Trugo
and Macrae, 1984b; Clifford, 1985; Tono et al., 1989; Ky et
al., 2001; Maria et al., 1994; Farah et al., 2005a, 2005b). A
low CGA content (1.2 %, dm) was found in beans of Coffea
pseudozanguebariae, a caffeine-free species native of East
Africa (Clifford and Ramirez-Martinez, 1991a). Such low
content has been also observed in some other low-caffeine or
caffeine-free species from Africa (Clifford, 1985).
In addition to the major chlorogenic acids cited above,
other minor compounds of the CGA family have been re-
ported. Recently, trace amounts of diferuloylquinic acids,
dimethoxycinamoylquinic acids, caffeoyl-dimethoxyci-
namoylquinic acids and feruloyl-dimethoxycinamoylquinic
acids were identied in Robusta coffee (Clifford et al.,
2006). CGA-caffeine complexes in coffee seeds have been
described (Clifford, 2000). The same CGA-protein complex-
es identied in coffee pulp were also identied in immature
coffee seeds (Grifn and Stonier, 1975, cited by Clifford,
1985). Small amounts of caffeic, ferulic, p-coumaric and
quinic acids may be found in green coffee beans in their
free form (Clifford 1985, Clifford, 1987). The occurrence of
cinnamoyl conjugates such as caffeoyl-tryptophan (Schrader
et al., 1996; Murata et al., 1995), p-coumaroyl-tryptophan
(Murata et al., 1995, Clifford, 1997), and caffeoyl-tyrosine
(Correia et al., 1995, Clifford, 1997) has also been reported,
but quantitative data is not available (Clifford, 2000). Al-
though CGA lactones are mostly produced during roasting of
the beans (see below), the presence of trace amounts of some
lactones, attributed to primary processing (for example, dry-
ing of the beans) has been reported in unroasted coffee beans
(Schrader et al., 1996; Farah et al., 2005a).
Table 2 presents the contents of the three main groups
of CGA in samples of green coffee beans, obtained by
chromatographic analytical methods. Considering the
nine main isomers of CGA: 5-CQA; 4-CQA and 3-CQA;
3,5-diCQA, 4,5-diCQA and 3,4-diCQA, 5-FQA, 4-FQA
and 3-FQA, in order of abundance in green coffee beans,
5-CQA alone is responsible for about 56-62 % of total
CGA. Considering that 4-isomers usually equal or slightly
exceed 3-isomers, 3-CQA and 4-CQA account for up
to 10% each of total CGA. DiCQA isomers account for
about 15-20% of total CGA in green coffee beans and FQA
isomers, for 5-13% of total CGA. p-CoQA isomers, CFQA
isomers and the newly identied diferuloyilquinic acids
and dimetoxycinnamoylquinic acid derivatives account
together for the remaining percentage (Clifford and Wight,
1976; Trugo and Macrae, 1984ab; Clifford, 1985; Shrader et
al., 1996; Clifford, 2003; Farah et al., 2001, 2005a, 2005b;
Farah, 2004; Clifford et al., 2006).
Not only total CGA content, but the CGA composition of
coffee beans also varies considerably during fruit maturation.
Considering variations between species and cultivars
(Ohiokpehai et al., 1982), a sigmoidal increase in total CQA,
mostly in parallel with the total dry matter gain, is initially
observed with maturation (Clifford and Kasi, 1987). The
ratio CQA/diCQA appears to increase with maturation until
ripeness of the fruit (Menezes, 1994a; Clifford and Kasi,
1987), probably due to hydrolysis of diCQA into mono-

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5
esters. At a certain stage before ripeness, CQA content starts
to drop, according to Montavón et al. (2003), due to oxidation.
From this point on, an inverse association between the levels
of CQA and coffee fruits maturation is observed (Menezes,
1994b). Recently, Farah et al (2005b) reported a reduction not
only in CQA levels, but also in FQA and diCQA levels, at this
last stage of maturation. The authors reported a total of 8.7 %
of CGA (dm) for immature C. arabica seeds (from dark green
fruits), while seeds of over-ripened fruits presented levels as
low as 1.3 %. Montavón et al (2003) suggested that unripe
seeds are more sensitive towards oxidation than ripe seeds
and that the lower sensitivity of ripe seeds occurs because the
defense mechanisms against oxidative stress become more
efcient during maturation. Alternatively, according to the
same authors, mature beans may contain lower polyphenol
oxidase and peroxidase activities than immature beans. This
hypothesis is in agreement with the reduction in polyphenol
oxidase activity observed at later stages of maturation
(Arcila-Pulgarin and Valência-Aristizabal, 1975; Mazzafera
and Robinson, 2000).
Despite the discrepancy caused by the use of different
analytical methods, the large variation in CGA content and
isomers distribution, along with qualitative differences
(presence and absence of some isomers) in green coffee
beans make the CGA content a potential criterion on coffee
genotype selection (Clifford et al., 1989; Correia et al.,
1995; Guerrero at al, 2001; Ky et al., 2001). A correlation
between the pattern of minor CGA-like compounds with
the geographical origin of the beans has been observed
and attributed to genetic factors rather than to agricultural
practices (Clifford and Jarvis, 1988; Correia et al., 1995).
However, as stated before, small variations in CGA content of
coffee beans from ripe fruits may be observed due to weather
and agricultural practices. Severe weather conditions such as
cold, high visible light and water stress conditions tend to
increase the contents of phenolic compounds not only in the
Table 2. Chlorogenic acids content in green coffee beans, expressed in g% a , dry matter basis.
Samples CQA FQA diCQA Total CGA References
C. arabica 5.76 0.25 0.87 6.88 Trugo & Macrae, 1984
C. arabica var
Caturra 4.63 0.33 0.66 5.62 Clifford & Ramirez-Martinez ,1991
C. arabica var. Bourbon 4.77 0.34 0.56 5.67 Clifford & Ramirez-Martinez ,1991
Wild C. arabica (average) 3.26 0.19 0.60 4.10 Ky et al., 2001
C. arabica (Angola) 4.30 0.57 1.23 6.10 Correia et al., 1995
C. arabica (Angola) 4.84 0.28 0.53 5.65 Correia et al., 1995
C. arabica (Angola) 5.67 0.79 1.39 7.85 Correia et al., 1995
C. arabica var Boubon (Brazil) 4.2 0.28 0.77 5.25 Farah et al., 2005a
C. arabica cv. Longberry (Ethiopia) 4.6 0.29 0.84 5.73 Farah et al., 2005a
C. canephora cv Robusta 6.82 0.60 1.37 8.80 Trugo & Macrae ,1984
C. canephora cv Robusta 5.33 0.79 1.05 7.17 Clifford & Ramirez-Martinez, 1991
C. canephora cv Robusta (Angola) 3.43 0.54 1.20 6.08 Correia et al., 1995
C. canephora cv Robusta (Angola) 4.97 0.75 1.46 7.18 Correia et al., 1995
C. canephora cv. Conillon (Brasil) 7.42 0.95 1.09 9.47 Farah et al., 2001
Wild C. canephora (average) 7.66 1.43 2.31 11.3 Ky et al., 2001
C. canephora var. Robusta (Uganda) 5.77 0.47 1.34 7.58 Farah et al., 2005a
Timor hybrid (C.arabica x C. canephora)4.71 0.33 0.58 5.62 Clifford and Ramirez-Martinez, 1991
Catimor (Timor hybrid x C. arabica)5.51 0.35 0.45 6.31 Clifford and Ramirez-Martinez, 1991
C. liberica cv. Dewevrei 5.39 0.48 1.1 6.97 Ky et al., 1977
CQA- caffeoyilquinic acid; FQA – feruloyiquinic acid; diCQA dicaffeoyilquinic acid. Total CGA – total chlorogenic acids. a Units may have been changed
for consistency a

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coffee plant and seed but also in other plants (Douglas, 1996;
Grace et al., 1998; Materska and Perucka, 2005; Pennycooke
et al., 2005). The use of nitrogen-rich fertilizers (Malta et al.,
2003) and situations of boron deciency (Camacho-Cristobal,
et al., 2002) have also shown to increase the content of total
CGA in coffee seeds and other plants.
Small amounts of phenolic compounds different
from CGA and related compounds have been identied
in green coffee beans. The presence of about 1 % of
phenolic glycosides has been suggested (Clifford, 1985).
Anthocyanidins such as cyanidins, pelargonidins and one
peonidin were identied in arabica coffee seeds as a residue
of red skin fruits. (Mazza and Miniati, 1993). Lignans
such as secoisolariciresinol, lariciresinol, matairesinol
and pinoresinol, in order of abundance, are also present
in coffee (Milder et al., 2005). Some free volatile phenols
have been identied (Moreira et al., 2000). Tannins have
not been identied in wet processed coffee seeds (Clifford
and Ramirez-Martinez, 1991a). However, it is possible that
dry processed beans contain a small amount of tannins as a
residue of the coffee fruits.
Biosynthesis of chlorogenic acids and relevance for the
plant physiology
CGA are products of the phenylpropanoid pathway, one
branch of the phenolic metabolism in higher plants that is
induced in response to environmental stress conditions such
as infection by microbial pathogens, mechanical wounding,
and excessive UV or high visible light levels (Herrmann,
1995; Haard and Chism, 1996). Plant phenolic acids
are synthesized from phenylalanine and tyrosine via the
shikimic acid pathway, which converts simple carbohydrate
precursors, derived from glycolysis and the pentose
phosphate shunt (phospho-enol-pyruvate and D-erythrose-
4-phosphate), into aromatic amino acids (gure 2). The
parent trans-cinnamic acid is formed from L-phenylalanine
by the action of phenylalanine ammonia-lyase, a key
enzyme in the biosynthesis of phenolic compounds that is
activated in response to different stress conditions. Quinic
acid is synthesized from 3-dehydroquinate, an intermediate
metabolite of the shikimic acid pathway. Hydroxy-cinnamic
acids (p-coumaric, caffeic, ferulic and sinapic) may be
synthesized from cinnamic acid by hydroxylation or
alternatively from tyrosine by the action of tyrosine amino-
lyase (gure 2).
The nal steps of biosynthesis of the 5-monoacyl CGA
(5-CQA, 5-FQA and 5-p-CoQA) have been studied in several
plants as well as coffee and appear to include binding of
trans-cinnamic acid to coenzyme A (CoA) by a CoA lyase,
followed by transfer to quinic acid by a cinnamoyl transferase
(Gross, 1981). The origin of the CGA with acyl groups in
positions 3- and 4- is unclear, although the possibility of acyl
migration has been considered (Gross, 1981). Once formed,
phenolic acids and CGA can be substrate of enzymes such
as polyphenol oxidase (Mazzafera and Robinson, 2000) and
Figure 2. Biosynthesis of cinnamic/hydroxycinnamic acids
and quinic acid via the shikimic acid pathway

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7
peroxidase (Takahama, 2004), leading to polymerization
products such as insoluble brown pigments and lignin
that contribute to the plant defense mechanisms and to the
synthesis of plant cell wall constituents.
Besides the recognition that CGA play an important role
in plant stress adaptation, there are indications that these
compounds may have specic physiological functions in
the coffee plant, consistent with the relatively high levels of
CGA usually found in coffee seeds (Clifford, 1987; Leloup et
al., 1995). CGA synthesis in the coffee plant may contribute
to the control of seed germination and cell growth, through
regulation of the levels of indolacetic acid - a plant growth
hormone of physiological signicance during the formation
and germination of the beans - and possibly also through
other still unknown mechanisms (Grifn and Stonier, 1975,
cited by Clifford, 1985; Clifford 1985).
CGA are found in the surface of coffee seeds, in
association with the cuticular wax, and in the cytoplasm
adjacent to the cell walls of the endosperm parenchyma
(Clifford, 1987), but there seem to be no reports whether the
distribution of CGA differ in these two locations. According
to Horman and Viani (1971, cited by Clifford, 1985) and
Zeller and Saleeb (1997), part of the cell wall CGA may
be associated with caffeine, as a 1:1 or 2:1 molar complex.
Although CGA are mostly found in the coffee seeds, they
have also been found in the leaves and in the coffee pulp
(Clifford and Ramirez- Martinez, 1991a).
Changes in chlorogenic acids composition of coffee beans
during processing
Roasting: In addition to their relevance for plant physiology
and for a potential use in the pharmacology eld, CGA
take part in the generation of color, avor and aroma of
coffee during roasting (Trugo and Macrae, 1984a; Moreira
et al., 2000; Montavón et al., 2003). Due to their thermal
instability, CGA may be almost completely degraded into
phenol derivatives when submitted to intense roasting
conditions. During roasting, part of CGA is isomerized,
part is transformed into quinolactones due to dehydration
and formation of an intramolecular bond (gure 3), and
part is hydrolyzed and degraded into low molecular weight
compounds (Trugo, 1984, Trugo and Macrae, 1984a; Leloup
et al., 1995; Clifford, 2000; Farah et al., 2005a). CGA also
participate in the formation of polymeric material like
melanoidins (Menezes, 1994a, Steinhart and Luger, 1997).
Drastic roasting conditions may produce losses of up to 95%
of CGA (Trugo, 1984), with 8-10% being lost for every 1%
loss of dry matter (Clifford, 1997, 1999, 2000). Total CGA
content in commercial roasted coffee ranges from about
0.5 to 7 % (table 3), depending on the type of processing,
roasting degree, blend and analytical conditions. CGA
contents in light or medium roasted coffees still stand out
when compared to most food sources of CGA (Farah et al.,
2001; Clifford, 2002). While coffee abstainers may typically
Figure 3. Formation of a 1,5-γ-quinolactone from chlorogenic acid during roasting (A), and the two major chlorogenic acid
lactones in roasted coffee: 3-caffeoylquinic-1,5-γ-lactone (left) and 4-caffeoylquinic-1,5-γ-lactone (right) (B) Although under
IUPAC rules the numbering system for the lactones is different from that for the acids, in order to avoid confusion, most
reports in the literature (including the present work) have been using for lactones the same numbering of the carbons as for
the acid precursors.

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A. FARAH and C. M. DONANGELO
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9
ingest less than 100 mg of CGA/day, modest and heavy
coffee drinkers intake may range from 0.1 to 2g (Clifford,
1997, 2000; Del Castillo et al., 2002).
In relation to changes in CGA individual subgroups and
isomers during roasting, at the beginning of the roasting process,
isomerization of CGA occurs. The levels of the substitutes of
the 5- position of the quinic acid decrease substantially while
the substitutes in the 3- and 4- positions increase in some cases
to almost double their original levels. (Trugo and Macrae,
1984; Leloup et al., 1995, Farah et al., 2005a). According
to Leloup et al (1995), at this roasting stage, diCQA may be
partially hydrolysed into monoesters and cafeic acid, which
may be again hydrolysed, decarboxylated and degraded to a
range of simple phenols. Levels of volatile phenols increase
along the process (Moreira et al., 2000). Chlorogenic acid
lactones formation occurs after 6 to 7% of weight loss (Hucke
and Maier, 1985; Farah et al., 2005a). About 7% of CGA in
regular Arabica coffee and 5.5% in Robusta coffee seem to
be transformed into 1,5-γ-quinolactones during the roasting
process (gure 3). Average lactones levels of 210 and 100
mg% (dm) were reported for commercial regular ground
coffee (Shrader et al., 1996) (table 3).
Table 3. Chlorogenic acids and quinolactones in ground roasted and instant coffee, expressed in % a, dry matter basis.
Coffee Samples CQA FQA Di
CQA
Total
CGA CQL FQL Di
CQL CoQL Total CGL References
Ground Roasted Coffee
Commercial 2.70 0.26 Bennat et al.,1994
2.64 0.34
1.94 0.23
0.81 0.17
1.00 0.16
Commercial
(average) 2.26 0.21 0.19 2.66 0.31 Shrader et al.,1996
Commercial 1.25 0.22 0.19 1.66 Monteiro & Trugo, 2005
1.29 0.19 0.24 1.72
0.85 0.12 0.09 1.06
0.38 0.06 0.03 0.47
C. arabicab Bourbon
(Brazil)
2.15 0.17 0.14 2.46 0.36 0.04 0.01 0.01 0.41 Farah et al., 2005a
C.arabica b
Longberry (Ethiopia)
1.65 0.15 0.13 1.93 0.33 0.04 0.01 0.01 0.38 Farah et al., 2005a
C. arabica 3.23 0.32 Bennat et al., 1994
C.arabica b
Decaffeinated
(average)
1.80 0.38 0.06 0.01 0.45 Farah et al., 2006b
C.canephora b
cv. Robusta
(Uganda)
2.76 0.34 0.23 3.33 0.39 0.03 0.03 0.45
Farah et al., 2005a
Instant Coffee
Non-decaffeinated 5.28 1.16 0,53 6.97 Trugo & Macrae, 1984a
Non-decaffeinated
0.63 0.06 0.03 0.72 Nogueira & Trugo, 2003
2.41 0.27 0.09 2.77
1.30 0.14 0.04 1.48
Decaffeinated 4.73 0.84 0.28 5.85 Nogueira & Trugo, 2003
3.33 0.60 0.17 4.10
a Units may have been changed for consistency; b. Laboratory roasted – light medium roast.

8
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A. FARAH and C. M. DONANGELO
PHENOLIC COMPOUNDS IN COFFEE
Braz. J. Plant Physiol., 18(1):_-__, 2006
9
The 3-caffeoylquinide or 3-caffeoylquinic-1,5-lactone
(3-CQL) is the main lactone, with maximum levels of
0.230 and 0.254 % (dm), in Arabica and Robusta coffees,
respectively (Farah et al., 2005a). The second major lactone
is 4-caffeoylquinic-1,5-lactone (4-CQL), with average
contents of 0.116 and 0.139 %, for Arabica and Robusta
coffees, respectively (Farah et al., 2005a). 3-CQL and 4-CQL
(gure 3) are expected to be the major 1,5-γ-quinolactones,
since caffeoylquinic acids are the main CGA and only those
CGA isomers that lack a substitute in the 5-position are able
to form a 1,5-γ-quinolactone. Lactone formation of 3-CQA
is favored relative to 4-CQA because of steric hindrance of
the ester group in axial position of the equatorial conformer
(Farah et al., 2005a). Lactones from FQA, diCQA and
p-CoQA, in order of relevance (table 3) and other minor
quinides, have also been identied in roasted coffee (Scholts
and Maier, 1990; Scholz-Bottcher et al., 1991; Flores-Parra
et al., 1989; Farah et al., 2005a).
The content of total CGA lactones increases until about
14% weight loss, i.e., light medium roast, reaching average
levels of 0.398 and 0.424 g% (dm) for Arabica and Robusta
coffees, respectively, and decreasing gradually thereafter
(Farah et al., 2005a, Bennat et al., 1994).
The extraction of chlorogenic acids into the beverage
depends on the grind of coffee, the proportion of coffee to
water, the brewing method, the water temperature and length
of time coffee is in contact with water, but domestic brewing
substantially extracts CGA (80-100%) and CGL from roasted
coffee (Clifford, 1997; 2000). Higher temperatures under
100ºC result in greater extraction of CGA (Trugo and Macrae,
1984a; Clifford, 1987). Extraction rate increases over the
rst 10 min commonly employed in domestic brewing. The
highest extraction rate of CGA usually occurs in the rst 2
min at 93ºC, increasing less rapidly thereafter (Merrit and
Proctor, 1959, Clifford, 1987). Domestic extraction will
result in 70-200 mg of CGA per 200ml cup, in the case of
Arabica coffee and 70-350 mg of CGA per 200 ml cup in
Robusta coffee (Clifford, 1997). Keeping coffee brews at an
elevated temperature reduces the contents of both CQA and
CQL in the brew (Bennat et al., 1994; Schrader et al., 1996).
Decaffeination: Moreira et al (2005) measured the contents
of CGA in ground and instant, light and dark roasted, regular
and decaffeinated Brazilian commercial coffee samples, and
observed lower CGA contents in all decaffeinated samples,
compared to non-decaffeinated ones. An average loss of 10%
was observed by Farah et al (2006b) in CGA contents of de-
caffeinated and roasted Arabica coffee samples, in compari-
son with non-decaffeinated samples roasted in the same con-
ditions. On the other hand, a 7% average increase in lactones
content was observed in the same samples (table 3).
Instant coffee processing: A large variation in the contents
of total CGA was observed upon analysis of thirteen
commercial instant coffee samples from England (3.6-10.7
%, dm -Trugo and Macrae, 1984b) and nine from Brazil
(0.6-5.9 %, dm - Nogueira and Trugo, 2003) (table 3). In
the respective samples, 5-CQA alone accounted for about
30% of total CGA; CQA accounted for 70%; FQA for 20%
and diCQA for 10%. The large difference in CGA levels was
attributed to the use of different blends and roasting degrees,
whereas the low percentage of diCQA was attributed to loss
during processing (Trugo and Macrae, 1984b, Nogueira and
Trugo, 2003). Bennat et al (1994) also performed analysis
of CQA and lactones in instant coffee and attributed the low
content of lactones to hydrolysis during processing.
Special types of processing
Steam-treated coffee: Coffee may be steam-treated prior to
roasting as a means to make coffee “less irritable” to the
stomach, and therefore acceptable to persons with stomach
problems (Steinhart and Luger, 1997). Degradation of CGA
during steaming of green beans has been reported as a
consequence of increased water uptake (Maier, 1994).
Monsooned coffee: This is a speciality coffee of India, which
undergoes a natural process of curing dry raw Arabica and
Robusta coffee beans by exposing them to moist monsoon
winds prevailing in the costal regions of Mangalore and
Tellichery. Variyar et al (2003) observed a substantial
decrease in CGA levels of this type of speciality coffee,
accompanied by an increase in the levels of free caffeic
acid, which was attributed to hydrolysis of CGA during the
process. Balyaya and Clifford (1995) also observed higher
levels of free caffeic acid in monsooned coffee beans.
Irradiation: This treatment has been applied to green beans
as a method to control microbiological contamination and
insect infestation. While Deshpande and Aguilar (1975) did
not observe differences in CGA and caffeic acid contents of
Arabica and Robusta beans treated with gamma irradiation,
Variyar et al. (2003) observed a substantial decrease in
CGA contents of irradiated beans in comparison with

10
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A. FARAH and C. M. DONANGELO
PHENOLIC COMPOUNDS IN COFFEE
Braz. J. Plant Physiol., 18(1):_-__, 2006
11
non-irradiated ones. The decrease in CGA level was not
accompanied by an increase in caffeic acid levels, which was
attributed to degradation of CGA, and not to hydrolysis, as
it was the case with monsooned beans. Gamma-irradiation
has been reported to reduce the contents of cinnamic acids in
food products (Clifford, 2000).
Chlorogenic acids composition and coffee quality
CGA are known to be important determinants of coffee
avor. They contribute to the nal acidity (Trugo and Macrae,
1984) and confer astringency (Carelli et al., 1974; Clifford
and Wight, 1976; Variyar et al., 2003) and bitterness (Trugo,
1984) to the beverage. As a result of Maillard and Strecker´s
reactions, bitterness increases during roasting due to release
of caffeic acid and formation of lactones and other phenol
derivatives responsible for avor and aroma (Ginz and
Enhelhardt, 1995; Maria et al., 1994, Variyar et al., 2003).
The relationship of CGA with coffee cup quality is still
unclear and somehow controversial. Okiokpehai (1982)
reported that the addition of diCQA conferred a disagreeable
avor to coffee beverage, which disappeared on subsequent
addition of CQA. However, according to Silva (1999),
total CGA levels present and inverse association with
coffee quality, with higher CGA content being observed
in lower quality samples. Considering that CQA accounts
for at least 60% of CGA contents in roasted coffee, higher
levels of CQA would be more likely to be associated with
low cup quality. Farah et al. (2006a) also observed a strong
association between the levels of CQA and FQA and low
cup quality. The decrease in quality was accompanied by an
increase in color intensity of raw beans that was attributed
indirectly to the presence of reactive orthoquinones formed
by the action of the enzyme polyphenol oxidase over these
compounds. Therefore, products of CGA oxidation may be
associated with cup quality decrease. This data, as well as the
data obtained by Silva (1999), are in agreement with reports
according to which orthoquinones are responsible for the
inhibition of the activity of polyphenol oxidase (Mazzafera
and Robinson, 2000). Coffee cup quality is directly related
to polyphenol oxidase activity and 5-CQA levels in seeds
from mature coffee fruits seem to be inversely associated
with polyphenol oxidase activity in coffee beans (Amorin
and Silva, 1968, Carvalho et al., 1994; Mazzafera, 1999;
Silva, 1999). Moreover, the fact that Amorim et al. (1975)
related oxidation products of phenolic compounds as a
possible cause for Rio-off-avor (a negative phenolic note
responsible for loss on cup quality) would strengthen the
hypothesis of the association between high levels of CQA
and FQA with low cup quality.
Amorin (1972) observed that 5-CQA levels above usual
levels for a determined species contributed to a decrease in
quality. Taking into account the well-known importance of
CGA for avor and aroma formation, there appears to be a
limiting high CGA level over which cup quality decreases.
Lower CGA levels also appear to explain the superiority
of C. arabica in beverage quality when compared with C.
canephora. The large difference in CGA contents of these
two species was considered one of the factors responsible
for avor differences between the two species (Trugo and
Macrae, 1984b; Ky et al., 2001; Bertrand et al., 2003).
The presence of defective coffee beans is also relevant in
establishing coffee quality. The CGA content of most defective
beans, excluding physical defects (bored, broken, etc.) and
defects of extraneous matter (husks, twigs, stones, etc.),
appears to vary according to the degree of maturation of the
fruit that generates the respective defect (Farah et al., 2005b).
The main defects occur due to strip-picking of immature and
overripe fruits along with ripe (cherry) fruits. The ve most
common defects in coffee that may considerably affect cup
quality are immature beans (originated from immature fruits),
immature-black beans (immature beans with oxidized skin),
black beans (from over-ripened fruits) and sour beans (from
fruits fermented on the ground or due to improper processing
conditions). Comparing immature and immature-black beans
with good quality beans, Mazzafera (1999) observed that the
contents of total phenolic substances and 5-CQA were higher
in immature and immature–black defective beans. Franca et
al. (2004) found lower levels of 5-CQA in black defective
beans, compared with good quality and immature defective
beans. After analysis of eight CGA isomers in defective coffee
beans, Farah et al. (2005b) also observed that immature and
immature-black defective beans contained signicantly
higher levels of all CGA isomers, particularly CQA and FQA,
compared to healthy and black defective beans. 5-CQA was
the main CGA in all defective beans (50-75% of total CGA),
varying from 5,6 % (dm) in dark green immature beans to
0,6 % (dm) in black defective beans, whereas good quality
samples had about 4 g% (dm). CGA isomers distribution was
similar in good quality beans, immature and immature-black
defective beans. However, sour and black defective beans
showed an increase of up to 25% in the isomers 3-CQA,
4-CQA and 4-FQA, in comparison with good quality beans,
probably due to the occurrence of isomerization of 5-CQA
and 5-FQA, and possibly hydrolysis of diCQA during the

10
Braz. J. Plant Physiol., 18(1):_-__, 2006
A. FARAH and C. M. DONANGELO
PHENOLIC COMPOUNDS IN COFFEE
Braz. J. Plant Physiol., 18(1):_-__, 2006
11
fermentative process (in the case of sour defects) or aging (in
the case of black defects).
Concluding remarks
The relatively high levels of phenolic acids, particularly
of chlorogenic acids and related compounds, in coffee
seeds reect their physiological importance for the coffee
plant, as well as their signicant contribution to aroma
and avor formation of coffee beverage. Genetic factors
such as species and variety, the degree of maturation, and
to some extent environmental conditions and agricultural
practices, are important determinants of the composition of
chlorogenic acids in green coffee beans, and will also affect
the composition of the nal beverage. Processing, especially
roasting, modies dramatically the phenolic composition
of coffee, producing aroma, avor and color compounds
characteristics of coffee beverage.
Although there is considerable published information
on total chlorogenic acids content in coffee, less is known
on the composition of specic chlorogenic acids isomers
and derived components such as lactones. The lack of
commercial standards for most of these compounds and
the similarity of their chemical structures require highly
sensitive chromatographic separation methods coupled to
mass spectrometry for proper identication and analysis.
More research is needed on these aspects and on the
composition of other phenolic compounds in coffee, as well
as their impact on cup quality. The effect of different types of
processing on coffee phenolic composition also needs to be
further explored.
Acknowledgements: The authors thank Daniel Perrone
Moreira for assistance with editing of the chemical structures.
Original research of the authors, cited in this review, was
funded in part by The CBPC - EMBRAPA, CAPES and
FAPERJ (Brasil), and by the Institute for Coffee Studies/
Vanderbilt University (EUA).
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