Proanthocyanidins in Cacao - Natural Antioxidants and Biocides from Wild Medicinal Plants - page 36

catechin content between Criollo and
Forastero types (Elwers et al. , 2009).
Trinitario (hybrids of criollo and foras-

et al. , 2009; Redovniković et al. , 2009; Liu,
2010). Epicatechin represents 2-4% of the dry
weight of defatted cocoa seed powder
(Niemenak et al. , 2006). Other flavonoids of
Theobroma cacao seeds include (2R,3S)-(+)-
catechin, (2R,3R)-(−)-epicatechin, and the dim-
ers epicatechin-(4b→8)-catechin (procyanidin
B1), epicatechin-(4b→8)-epicatechin (procya-
nidin B2), epicatechin-(4b→6)-epicatechin and
the trimer epicatechin-(4b→8)-epicatechin,
epicatechin-(4b→8)-epicatechin (procyanidin
C1) (Porter et al ., 1991). Three other more
complex compounds, 3- O -b-D-galactopyranosyl
ent- epicatechin-(2a→7, 4a→8)-epicatechin,
3- O -L-arabinopyranosyl ent- epicatechin-
(2a→7, 4a→8)-epicatechin and epicatechin-
(2b→5, 4b→6)-epicatechin were also isolated
from fractions of the seed extracts (Porter
et al. , 1991; Tückmantel et al. , 1999).
The procyanidins in cocoa were estab-
lished by column chromatography, thin-layer
chromatography (TLC), high-performance
liquid chromatography (HPLC) and negative
ion fast atom bombardment mass spectro-
metry (FAB/MS) to include oligomers
through heptamers (Porter et al. , 1991). This
work established that the structures through
tetramers consisted primarily of (−)-epicate-
chin units. Later work (Clapperton et al. ,
1992) established the structures through
octamers with a combination of column
chromatography, reversed-phase HPLC, and
positive ion liquid secondary ion (LSI) mass
spectrometry. In subsequent studies, the
investigators used normal-phase HPLC cou-
pled with atmospheric pressure ionization
with electrospray (API-ES) mass spectrome-
try to measure the degree of polymerization
of the seeds of Theobroma cacao and choco-
late, and to separate and simultaneously
identify groups of procyanidin oligomers
(Hammerstone et al. , 1999). Sodium ion was
also used to assist ionization of the proan-
thocyanidins. Monomers through decamers
were observed (Wollgast et al ., 2001; Counet
et al. , 2004). Oligomers from tetramers to
decamers also formed multiply charged ions.
Although proanthocyanidin with epi-
catechin units are the major components
in unprocessed cacao, (+)-catechin has
been found in unfermented, dried cocoa
beans, and epimerization of (−)-epicatechin

•

tero forms). These hybrids, which origi-
nated in Trinidad, are sometimes classified
as a subgroup of the forasteros (Gómez-
Pompa et al. , 1990). Because they are
hybrids, they are highly variable from
seed, unless the seed is derived from
known crosses. The seed quality is
intermediate between that of the criol-
los and the forasteros, as are other char-
acteristics. Several previous workers
failed to find significant differences in
polyphenol and catechin content among
Criollo, Forastero and Trinitario types
(Elwers et al. , 2009) This classification
into subspecies and hybrids is still used
in worldwide cocoa trade, but recent
results of molecular studies led to the
recognition of ten genetic clusters of
cocao instead of two genetic groups
(Motamayor et al. , 2008).

Phenolic compounds represent a large
group of molecules widely distributed in
the plant kingdom, where they have a vari-
ety of functions in growth, development
and defence. Although there does not seem
to be a significant difference in the amount
of procyanidins between the major types of
cacao, there is major seed-to-seed variation
in the amounts encountered (Niemenak
et al. , 2006); flavan-3-ols, anthocyanins and
proanthocyanidins are responsible for most
of the bitter and astringent flavours of choc-
olate products. The aroma compounds of
cacao are largely due to reducing sugars,
free amino acids and oligopeptides that
arise during the fermentation and drying
processes (Schwan and Wheals, 2004) and
undergo non-enzymatic Maillard reactions
during drying and roasting. The alkaloids
theobromine and caffeine also contribute to
bitter tastes in cacao products.

3.2 Raw Cacao Beans

Proanthocyanidins accumulate from approx-
imately 6.9% to levels as high as 18% dry
weight of seeds of Theobroma cacao (Elwers