coffee plant and seed but also in o

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 deficiency (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 identified
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 identified 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 identified (Moreira et al., 2000). Tannins have
not been identified 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 pulp.
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 (figure 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 aminolyase
(figure 2).
The final 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

Hasil (Bahasa Indonesia) 2:

tanaman kopi dan biji tetapi juga pada tanaman lain (Douglas, 1996;
Rahmat et al, 1998;. Materska dan Perucka, 2005; Pennycooke
. et al, 2005). Penggunaan kaya nitrogen pupuk (Malta et al.,
2003) dan situasi kekurangan boron (Camacho-Cristobal,
et al., 2002) juga telah ditunjukkan untuk meningkatkan kandungan total
CGA dalam biji kopi dan tanaman lainnya.
Sejumlah kecil fenolik senyawa yang berbeda
dari CGA dan senyawa terkait telah diidentifikasi
dalam biji kopi hijau. Kehadiran sekitar 1% dari
glikosida fenolik telah disarankan (Clifford, 1985).
Anthocyanidins seperti cyanidins, pelargonidins dan satu
peonidin diidentifikasi dalam biji kopi arabika sebagai residu
dari buah kulit merah. (Mazza dan Miniati, 1993). Lignan
seperti secoisolariciresinol, lariciresinol, matairesinol
dan pinoresinol, dalam rangka kelimpahan, juga hadir
dalam kopi (lebih ringan et al., 2005). Beberapa fenol volatil gratis
telah diidentifikasi (Moreira et al., 2000). Tanin telah
belum teridentifikasi di basah biji kopi olahan (Clifford
dan Ramirez-Martinez, 1991a). Namun, ada kemungkinan bahwa
biji diproses kering mengandung sejumlah kecil tanin sebagai
residu dari pulp kopi.
Biosintesis asam klorogenat dan relevansi untuk
fisiologi tanaman
CGA adalah produk dari jalur fenilpropanoid, salah satu
cabang dari metabolisme fenolik pada tanaman yang lebih tinggi yang
diinduksi dalam menanggapi kondisi stres lingkungan seperti
infeksi oleh mikroba patogen, luka mekanik,
dan UV yang berlebihan atau tingkat cahaya tampak tinggi (Herrmann,
1995; Haard dan Chism, 1996). Asam pabrik fenolik
disintesis dari fenilalanin dan tirosin melalui
jalur shikimat asam, yang mengubah karbohidrat sederhana
prekursor, yang berasal dari glikolisis dan pentosa
shunt fosfat (phospho-enol-piruvat dan D-erythrose-
4-fosfat), menjadi asam amino aromatik ( gambar 2). The
orangtua asam trans-sinamat dibentuk dari L-fenilalanin
oleh aksi fenilalanin amonia-lyase, kunci
enzim dalam biosintesis senyawa fenolik yang
diaktifkan dalam menanggapi kondisi stres yang berbeda. Quinic
asam disintesis dari 3-dehydroquinate, perantara
metabolit dari jalur asam shikimat. Hidroksi-sinamat
asam (p-coumaric, caffeic, ferulic dan sinapic) dapat
disintesis dari asam sinamat oleh hidroksilasi atau
alternatif dari tirosin oleh aksi tirosin aminolyase
(gambar 2).
Langkah-langkah akhir dari biosintesis dari 5-monoacyl CGA
( 5-CQA, 5-FQA dan 5-p-CoQA) telah dipelajari di beberapa
tanaman serta kopi dan tampaknya termasuk mengikat
asam trans-sinamat ke koenzim A (CoA) oleh lyase CoA,
diikuti dengan transfer ke quinic asam oleh transferase sinamoil
(Gross, 1981). Asal CGA dengan kelompok asil di
posisi 3 dan 4- tidak jelas, meskipun kemungkinan asil
migrasi telah dianggap (Gross, 1981). Setelah terbentuk,
asam fenolik dan CGA dapat substrat enzim tersebut
sebagai polifenol oksidase (Mazzafera dan Robinson, 2000) dan