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Neurochemical Research
ISSN 0364-3190
Neurochem Res
DOI 10.1007/s11064-012-0935-6
Comparative Study on the Inhibitory Effect
of Caffeic and Chlorogenic Acids on Key
Enzymes Linked to Alzheimer’s Disease and
Some Pro-oxidant Induced Oxidative Stress
in Rats’ Brain-In Vitro
Ganiyu Oboh, Odunayo M.Agunloye,
Ayodele J.Akinyemi, Adedayo
O.Ademiluyi & Stephen A.Adefegha
1 23
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ORIGINAL PAPER
Comparative Study on the Inhibitory Effect of Caffeic
and Chlorogenic Acids on Key Enzymes Linked to Alzheimer’s
Disease and Some Pro-oxidant Induced Oxidative Stress in Rats’
Brain-In Vitro
Ganiyu Oboh •Odunayo M. Agunloye •
Ayodele J. Akinyemi •Adedayo O. Ademiluyi •
Stephen A. Adefegha
Received: 5 August 2012 / Revised: 12 November 2012 / Accepted: 16 November 2012
ÓSpringer Science+Business Media New York 2012
Abstract This study sought to investigate and compare
the interaction of caffeic acid and chlorogenic acid on
acetylcholinesterase (AChE) and butyrylcholinesterase
(BChE), and some pro-oxidants (FeSO
4
, sodium nitro-
prusside and quinolinic acid) induced oxidative stress in rat
brain in vitro. The result revealed that caffeic acid and
chlorogenic acid inhibited AChE and BChE activities in
dose-dependent manner; however, caffeic acid had a higher
inhibitory effect on AChE and BChE activities than
chlorogenic acid. Combination of the phenolic acids
inhibited AChE and BChE activities antagonistically.
Furthermore, pro-oxidants such as, FeSO
4
, sodium nitro-
prusside and quinolinic acid caused increase in the mal-
ondialdehyde (MDA) contents of the brain which was
significantly decreased dose-dependently by the phenolic
acids. Inhibition of AChE and BChE activities slows down
acetylcholine and butyrylcholine breakdown in the brain.
Therefore, one possible mechanism through which the
phenolic acids exert their neuroprotective properties is by
inhibiting AChE and BChE activities as well as preventing
oxidative stress-induced neurodegeneration. However,
esterification of caffeic acid with quinic acid producing
chlorogenic acid affects these neuroprotective properties.
Keywords Caffeic acid Chlorogenic acid
Acetylcholinesterase Butyrylcholinesterase
Malondialdehyde
Introduction
In recent years, studies have implicated oxidative stress to
play a crucial role in neurodegenerative diseases such as
Alzheimer’s disease via lipid peroxidation of cell mem-
brane of the neurons [1]. The brain and nervous system are
thought to be particularly vulnerable to oxidative stress due
to limited antioxidant capacity, consumption of 20 % of
metabolic oxygen, inability of the neurons to synthesize
glutathione and high lipid content [2,3]. However, one
practical way to prevent/or manage neurodegenerative
diseases is through consumption of foods rich in antioxi-
dants (dietary means).
Alzheimer’s disease (AD) is the most common form of
age-related dementia and is characterized by progressive
and insidious neurodegeneration of the central nervous
system that eventually leads to a gradual decline of cog-
nitive function and dementia. Elements receiving the most
attention in Alzheimer disease are aluminum (Al), mercury
(Hg), and iron (Fe) [4–6]; of these, iron may have the most
important pathophysiologic role as a catalyst for free rad-
ical generation by virtue of having a loosely bound electron
and the ability to exist in more than one valence [6]. The
mechanism by which iron can cause this deleterious effect
is that Fe(II) can react with hydrogen peroxide (H
2
O
2
)to
produce the hydroxyl radical (OH) via the Fenton reaction,
whereas superoxide can react with iron(III) to regenerate
iron(II) which will participate in the Fenton reaction [7].
The overproduction of ROS can directly attack the
G. Oboh (&)O. M. Agunloye A. J. Akinyemi (&)
A. O. Ademiluyi S. A. Adefegha
Functional Foods, Nutraceuticals and Phytomedicine Unit,
Department of Biochemistry, Federal University of Technology,
Akure, P.M.B. 704, 340001 Akure, Nigeria
e-mail: goboh2001@yahoo.com
A. J. Akinyemi
e-mail: ajakinyemi2010@yahoo.co.uk
A. J. Akinyemi
Department of Biochemistry, Afe Babalola University,
Ado-Ekiti, P.M.B. 5454, Ado-Ekiti, Nigeria
123
Neurochem Res
DOI 10.1007/s11064-012-0935-6
Author's personal copy
polyunsaturated fatty acids of the cell membranes and
induce lipid peroxidation.
Although the etiology of AD is not fully understood,
nevertheless, inhibition of acetylcholinesterase (AChE) and
butyrylcholinesterase (BChE) activity has been accepted as
an effective treatment/management strategy against AD [8,
9]. AChE inhibitors such as tacrine, donepezil and riv-
astigmine are commonly used synthetic drugs for the
treatment of Alzheimer’s disease; however, these drugs are
limited in use due to their adverse side effects and are
effective only against the mild type of AD. In addition,
there is presently no drug available with BChE inhibitory
activity [10]. However, there are growing evidences that
BChE may be one of the important enzymes involved for
AD, where decrease in AChE activity and increased BChE
activity in 40–90 % of AD sufferers is observed [11].
Hence, recent efforts have focused on plant phytochemicals
as natural sources of effective acetylcholinesterase and
butyrylcholinesterase inhibitors with little or no side effects
which could be used as dietary intervention in the man-
agement of neurodegenerative diseases [9,12].
Several epidemiological and clinical studies have shown
inverse association between the consumption of polyphe-
nols or polyphenol-rich foods and the risk of several neu-
rodegenerative diseases including Alzheimer’s disease and
Parkinson’s disease [13]. Polyphenols are the most abun-
dant antioxidants in human diet and are widespread con-
stituents of fruits and vegetable [3]. Phenolic acids account
for one-third of all polyphenols present in plants and there
is an increasing awareness and interest in this group
because of their abundance in plant foods daily consumed
by humans and the estimated daily consumption ranged
between 25 and 1 g [14]. Hydroxylbenzoic acids and
hydroxycinnamic acids represent the major class of phe-
nolic acid found in almost every plant [15]. Caffeic acid
and chlorogenic acid are the major representative of
hydroxycinnamic acids widely distributed in plant tissues
and they occur in foods such as fruits, spices, vegetables,
wine, olive oil, and coffee [14]. Considerable amounts of
experimental data on the antioxidant activity of both caf-
feic acid and chlorogenic acid with emphasis on structure–
function antioxidant activity have been reported [16,17].
Furthermore, phenolic acids have been shown to have
antitumor [17,18], anti-inflammatory [17,19] and anti-
Alzheimer’s properties [20,21]. Although, phenolic acids
have been shown to possess anti-Alzheimer’s properties,
but there are dearth of information on how they exert this
effect. Hence, this study sought to investigate and compare
the inhibitory effect of caffeic acid and chlorogenic acid on
acetylcholinesterase and butyrylcholinesterase activities,
and some pro-oxidant induced oxidative stress in rats’
brain with the aim of determining some possible mecha-
nisms by which they exerts their neuroprotective effect.
Experimental Procedure
Chemicals and Reagents
Chemicals such as caffeic acid, chlorogenic acid, thiobarbituric
acid (TBA), ABTS (2,20-azino-bis(3-ethylbenzthiazoline-6-
sulphonic acid), acetylthiocholine iodide, butyrylthiocholine
iodide and 5,5-dithio-bis(2-nitrobenzoic acid) were purchase
from Sigma-Aldrich, Chemie GmH (Steinheim, Germany),
acetic acid was procured from BDH Chemical Ltd., (Poole,
England), quinolinic acid and K
2
S
2
O
8
were sourced from
Sigma-Aldrich (St Louis, MO). Except otherwise stated, all
other chemicals and reagents are of analytical grade while the
water was glass distilled.
Experimental Animals
Twenty male Wistar strain rats weighing between 190 and
250 g were purchased from the Central Animal House,
Department of Biochemistry, University of Ilorin, Ilorin,
Nigeria. They were housed in stainless steel cages under
controlled conditions of a 12 h light/dark cycle, 50 %
humidity, and 28 °C temperature. The rats were allowed
asses to food and water ad libitum. The handling and use of
experimental animals are as approved by the Animal Ethics
Committee of the Federal University of Technology,
Akure, Nigeria, and was in accordance with the NIH guide
for the use and handling of experimental animals.
Acetylcholinesterase and Butyrylcholinesterase
Inhibition Assay
Inhibition of AChE was assessed by a modified colori-
metric method of Ellman [22]. The AChE activity was
determined in a reaction mixture containing 200 lLofa
solution of AChE (0.415 U/mL in 0.1 M phosphate buffer,
pH 8.0), 100 lL of a solution of 5,50-dithiobis(2-nitro-
benzoic) acid (3.3 mM DTNB in 0.1 M phosphate buffered
solution, pH 7.0, containing 6 mM NaHCO
3
), caffeic acid
or chlorogenic acid solution (2.5–12 lg/mL) and 500 lL
of phosphate buffer, pH 8.0. After incubation for 20 min at
25 °C, 100 lL of 0.05 mM acetylthiocholine iodide solu-
tion was added as the substrate, and AChE activity was
determined as changes in absorbance reading at 412 nm for
3 min at 25 °C using a spectrophotometer. 100 lLof
butyrylthiocholine iodide was used as a substrate to assay
butyrylcholinesterase activity, while all other reagents and
conditions were the same. The AChE and BChE inhibitory
activities were expressed as percentage inhibition while the
concentration of the phenolic acids (caffeic acid and
chlorogenic acids) causing 50 % inhibition of the AChE
and BChE activity (IC
50
) was calculated by nonlinear
regression analysis.
Neurochem Res
123
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Lipid Peroxidation and Thiobarbituric Acid Reactions
The rats were decapitated via cervical dislocation and the
cerebral tissue (whole brain) was rapidly dissected, placed
on ice and weighed. This tissue was subsequently rinsed in
cold saline solution and later homogenized in phosphate
buffer pH 7.4 (1:5 w/v) with about 10-up and -down strokes
at approximately 1,200 rev/min in a Teflon-glass homoge-
nizer. The homogenate was centrifuged for 10 min at
3,0009gto yield a pellet that was discarded and the super-
natant was used for lipid peroxidation assay [23] and source
of enzyme for AChE and BChE inhibitory assays. The lipid
peroxidation assay was carried out using a modified method
of Ohkawa et al. [24]. Briefly, 100 lL of the tissue super-
natant was mixed with a reaction mixture containing 30 lL
of 0.1 M Tris–HCl buffer (pH 7.4), caffeic acid or chloro-
genic acid solution (1.56–6.25 lg/mL) and 30 lLof
250 lM freshly prepared FeSO
4
(the procedure was also
carried out using 7 mM sodium nitropurisside and 15 mM
Quilinonic acid). The volume was made up to 300 lL with
distilled water before incubation at 37 °C for 1 h. Subse-
quently, 300 lL of 8.1 % sodium dodecyl sulphate (SDS),
500 lL of acetic acid/HCl buffer (pH 3.4) and 500 lLof
0.8 % thiobarbituric acid (TBA) were added to the reacting
mixture. This mixture was incubated at 100 °C for 1 h and
Thiobarbituric acid reactive species (TBARS) produced
were measured at 532 nm using a spectrophotometer. Mal-
ondialdehyde (MDA) was used as standard and TBARS
produced was reported as MDA equivalent.
Determination of Total Antioxidant Capacity
The total antioxidant capacity of the of the phenolic acids
(caffeic and chlorogenic acids) was determined as a mea-
sure of their 2,20-azino-bis(3-ethylbenzothiazoline-6-sul-
phonic acid (ABTS) radical scavenging ability as described
by Re et al. [25]. ABTS
?
was generated by reacting ABTS
aqueous solution (7 mM) with K
2
S
2
O
8
(2.45 mM, final
concentration) in the dark for 16 h and adjusting the Abs
734 nm to 0.700 with ethanol. 0.2 mL of appropriate
dilution (0.1 mg/mL) of the phenolic acids (caffeic and
chlorogenic acids) was added to 2.0 mL ABTS
?
solution
and the absorbance was measured at 734 nm after 15 min.
The Trolox equivalent antioxidant capacity (TEAC) was
subsequently calculated using Trolox as the standard.
Data Analysis
The result of replicate experiments (n=6) were pooled
and expressed as mean ±standard deviation (SD). The
means were analyzed using one-way analysis of variance
(ANOVA) and Duncan test was used for the post hoc
treatment. Significance was accepted at PB0.05.
Results
The ability of the phenolic acids (caffeic and chlorogenic
acids) to inhibit acetylcholinesterase (AChE) and butrylcho-
linesterase (BChE) activity in vitro was investigated and the
result is presented in Fig. 1a, b respectively. The result
revealed that both phenolic acids inhibited AChE and BChE
activities in a dose-dependent manner (0–12 lg/mL). How-
ever, the IC
50
(concentration of sample causing 50 % enzyme
inhibition) value (Table 1) revealed that, caffeic acid had a
significantly (P\0.05) higher inhibitory effect on AChE
(IC
50
=4.21 lg/mL) and BChE (IC
50
=5.6 lg/mL) activi-
ties than chlorogenic acid [AChE (IC
50
=8.01 lg/mL) and
BChE (IC
50
=6.3 lg/mL)].
Furthermore, the effect of combination of the two phe-
nolic acids on their inhibitory effect on AChE and BChE
activities in vitro was also investigated and the result is
presented in Fig. 2. The result revealed that the effect of
combination of the two phenolic acids on both AChE and
BChE activity resulted into marked alteration in their
inhibitory activity. The highest inhibition of the enzymes
was recorded at 100 % inclusion of caffeic acid (CA).
However, a gradual decrease in the inhibition of the enzymes
(AChE and BChE) was observed as the concentration of
(a)
d
c
b
a
d
c
b
a
0
10
20
30
40
50
60
70
02468101214
Sample Concentration (µg/mL)
caffeic acid
chlorogenic acid
(b)
d
c
b
a
d
c
b
a
0
10
20
30
40
50
60
02468101214
Sample Concentration (µg/mL)
caffeic acid
chlorogenic acid
Butyrylcholinesterase
Inhibition (%)
Acetylcholinesterase
Inhibition (%)
Fig. 1 a Inhibition of acetylcholinesterase activity by caffeic and
chlorogenic acids and bInhibition of butyrylcholonesterase activity
by caffeic and chlorogenic acid. Values represent mean ±standard
deviation (n =6). Bars with the same letters are not significantly
different (P[0.05)
Neurochem Res
123
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chlorogenic acid increases from 100 % (CH) to 50 %
(CCH). Nevertheless, the highest AChE inhibition was
observed at 75 % inclusion of caffeic acid (CAM).
The effect of the phenolic acids (caffeic and chlorogenic
acid) on Fe
2?
-induced oxidative stress in isolated rat brain
homogenates is presented in Fig. 3. The result revealed that
incubation of rat brain in the presence of 250 lMFe
2?
caused a significant increase in the MDA content, never-
theless, both phenolic acids caused a significant (P\0.05)
decrease in the MDA content of the brain in a dose-
dependent manner (1.56–6.25 lg/mL). However, there
exist no significant (P[0.05) difference between their
inhibition of Fe
2?
-induced oxidative stress in rat brain
homogenates. Furthermore, the effect of the phenolic acids
on sodium nitroprusside (SNP) induced oxidative stress in
isolated rat brain homogenates is represented in Fig. 4. The
study revealed that, incubating rat brain tissue homoge-
nates in the presence of 7 mM SNP resulted in a significant
(P\0.05) increase in the MDA production in the brain;
however, the presence of the phenolic acids (caffeic and
chlorogenic acids) caused significant (P[0.05) decrease
in the MDA content of the brain in dose-dependent manner
(1.56–6.25 lg/mL). Nevertheless, there was no significant
difference (P[0.05) in their inhibition of SNP-induced
oxidative stress in rat brain. In like manner, effect of the
phenolic acids (caffeic and chlorogenic acids) on quino-
linic acid (QA)-induced oxidative stress in isolated rat
brain tissue homogenates was also studied and the result is
represented in Fig. 5. The result revealed that incubation of
the rat brain tissue homogenates in the presence of 15 mM
QA caused a significant (P\0.05) increase in MDA
production in the brain, which the phenolic acids were able
Table 1 Total antioxidant capacity and IC
50
(concentration of sample causing 50 % enzyme inhibition) value of acetycholinesterase and
butyrylcholinesterase inhibitory activity of caffeic and chlorogenic acids
Sample Total antioxidant capacity
(mmol TEAC/100 g)
IC
50
(lg/mL)
Acetycholiesterase Butyrylcholinesterase
Caffeic acid 4.37 ±1.20
a
4.21 ±0.02
b
5.60 ±0.01
c
Chlorogenic acid 3.80 ±0.81
a
8.01 ±0.01
c
6.30 ±0.02
d
Values represent mean ±standard deviation (n=6)
Values with the same superscript letter on the same column are not significantly different (P[0.05)
a
b
c
db
ab
ccc
0
15
30
45
60
75
90
CA CAM CCH CHM CH
Sample Combination Ratio
Enzyme Inhibition (%)
Acetylcholinesterase activity
Butyrylcholinesterase activity
Fig. 2 Inhibitory effect of combination of the phenolic acids (caffeic
and chlorogenic acids) on acetylcholinesterase and butyrylcholinest-
erase activity. CA—100 % caffeic acid, CH—100 % chlorogenic
acid, CAM—75 % caffeic acid/25 % chlorogenic acid, CCH—50 %
caffeic acid/50 % chlorogenic acid and CHM—25 % caffeic acid/
75 % chlorogenic acid. Values represent mean ±standard deviation
from independent experiments (n =6). Bars with the same letters are
not significantly different (P[0.05)
d
c
b
a
a
b
cd
40
60
80
100
120
140
160
01234567
Sample Concentration (µg/mL)
MDA Produced (% Control)
caffeic acid
chlorogenic acid
Fig. 3 Inhibition of Fe
2?
induced lipid peroxidation in rat brain by
caffeic acid and chlorogenic acids. Values represent mean ±standard
deviation (n =6)
d
c
b
a
ab
c
d
0
50
100
150
200
01234567
Sample Concentration ( µg/mL)
MDA Produced (% Control)
caffeic acid
chlorogenic acid
Fig. 4 Inhibition of sodium nitroprusside (SNP) induced oxidative
stress in rat brain by caffeic acid and chlorogenic acids. Values
represent mean ±standard deviation (n =6)
Neurochem Res
123
Author's personal copy
to significantly (P\0.05) inhibit in a dose-dependent
manner (1.56–6.25 lg/mL). Nevertheless, caffeic acid
exhibit higher inhibition of QA-induced MDA production
in the rat brain tissue homogenates than chlorogenic acid
(Fig. 6).
In addition, the total antioxidant capacity of the phenolic
acids (caffeic and chlorogenic acids) reported as TROLOX
equivalent antioxidant capacity (TEAC) is as presented in
Table 1. The result showed that both phenolic acids are
strong antioxidant molecules capable of scavenging ABTS
radicals in vitro. However, caffeic acid (4.37 mmol.TEAC/
100 g) had a significantly (P\0.05) higher total antioxi-
dant capacity than chlorogenic acid (3.70 mmol.TEAC/
100 g).
Discussion
This present study was designed to assess the neuropro-
tective activities of caffeic acid and chlorogenic acid
through their inhibition of AChE and BChE as well as
some pro-oxidants induced oxidative stress in isolated rat
brain homogenates in vitro. The observed inhibition of both
AChE and BChE activities by the phenolic acids (caffeic
and chlorogenic acid) is consistent with earlier studies on
polyphenolic compounds [26,27]. Inhibition of acetyl-
cholinesterase (AChE) and butyrylcholinesterase (BChE)
activity has been accepted as an effective treatment/man-
agement strategy against AD [28]. Inhibition of AChE and
BChE activity prevents it from breaking down acetylcho-
line and butyrylcholine in the brain and consequently
increased the concentrations of the neurotransmitter at the
synaptic cleft which leads to increased communication
between the nerve cells that use acetylcholine or butyr-
ylcholine as a chemical messenger; thus temporarily
improve or stabilize the symptoms of Alzheimer’s disease
[28]. However, the higher inhibitory effect of caffeic acid
on both AChE and BChE activities as compared with
chlorogenic acid could be structure related. Studies have
shown that cholinesterase inhibitory effect of polyphenolic
compounds is a function of number and position of their
OH groups which forms hydrogen bonds with specific
amino acids at the enzymes’ active sites [27,29]. However,
the substitution of quinic acid for an OH group in chloro-
genic acids may have influenced its inhibitory properties.
Furthermore, the affinity for binding to AChE and BChE
thus causing inhibition was lower for chlorogenic acid,
probably because the substituted quinic acid produces
steric constraints for accommodation to the active site of
both enzymes. Orhan et al. [29] reported quinic acid as not
exhibiting both AChE and BChE inhibitory activity and
this also could have influenced the inhibitory capacity of
chlorogenic acid.
Numerous plants and their constituents are reputed in
folk medicine for the enhancement of cognitive function
and to alleviate other symptoms of AD, including depres-
sion. These plant constituents may not only act synergis-
tically with other constituents from the same plant, but may
also enhance the activity of compounds from other plant
species. This approach has been used in various practices
of traditional medicine where mixture of plants is com-
monly prescribed [28]. However, the observed reduction in
the enzyme inhibitory properties when the phenolic acids
were combined could be as a result of the antagonistic
effect of chlorogenic acid on caffeic acid. The presence of
quinic acid moiety on the chlorogenic acid structure could
have affected the interaction of the phenolic acids with the
active site of both AChE and BChE causing significant
reduction in their enzyme inhibitory activity. This could
also explain the high enzyme inhibitory effect observed at
75 and 100 % inclusion of caffeic acid. Nevertheless, this
finding contradicts the findings of Oboh et al. [30] where
d
c
b
a
a
b
c
d
0
50
100
150
200
250
300
01234567
Sample Concentration (µg/mL)
MDA Produced (% Control)
caffeic acid
chlorogenic acid
Fig. 5 Inhibition of quinolinic (QA) induced oxidative stress in rat
brain by caffeic acid and chlorogenic acids. Values represent
mean ±standard deviation (n =6)
Fig. 6 Structure showing acaffeic acid and bchlorogenic acid
Neurochem Res
123
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combination of red and white ginger inhibited acetylcho-
linesterase (AChE) activity synergistically in vitro.
The observed inhibition of MDA production in rat brain
tissue homogenates under the influence of some pro-oxi-
dants (Fe
2?
, sodium nitroprusside and quinolinic acid)
gives credence to the fact that these phenolic acids are
strong antioxidant compounds (Table 1). Fe
2?
participates
in the Fenton’s reaction which leads to production of
reactive oxygen species causing damage to membrane
lipids and ultimately cell death. Elevated brain content of
Fe
2?
had been linked to some neurodegenerative diseases
with elevated Fe levels localized in degenerate regions of
Alzheimer brain in human and animal models of the dis-
ease [31]. Furthermore, NO a major metabolite of sodium
nitroprusside could react with superoxide forming powerful
peroxynitrite which induces lipid peroxidation and protein
and nucleic oxidation, thereby contributing to neurode-
generation through ATP-dependent PARP (poly ADP–
ribose polymerase) over activation of neurons, causing
neuronal ATP depletion, mitochondrial dysfunction,
inflammation and ultimately, cell death [32]. Quinolinic
acid (QA) has been reported to activate neurons expressing
NMDA receptors and glutamate-type excitotoxicity [33],
and QA-induced neuronal oxidative stress results from
overstimulation of NMDA receptors. Elevated QA levels
have been associated with several neurodegenerative dis-
eases including Alzheimer’s disease [34]. Nevertheless, the
inhibition of these pro-oxidants induced oxidative stress in
the rat brain homogenate is consistent with earlier studies
on plant phytochemicals, which was attributed to their
antioxidant properties such as Fe
2?
chelation and free
radical scavenging ability [35,36].
Neurodegeneration due to oxidative stress has been
implicated in the pathogenesis and progression of AD, with
selective loss of cholinergic neurons in the brain being the
most prominent. Studies have reported the AD brain to be
under intensive oxidative stress [37] and decrease in the
cholinergic neurons has been shown to promote amyloid
protein deposition in the AD brain which in turn favour
amyloid protein-associated oxidative stress and neurotox-
icity [38]. Hence, augmenting/improvement in the body’s
antioxidant status through dietary means could be practical
approach through which oxidative stress-induced neuro-
degeneration is controlled.
Chlorogenic acid is formed from the esterification of
caffeic acid with quinic acid. Several studies have reported
absorption, metabolism and distribution of these phenolic
acids in intact animals and cell lines minutes after exposure
[39–41]. Furthermore, Ito et al. [42] reported that Chloro-
genic acid acts on the CNS through the blood–brain barrier
either in its intact form or as a metabolite. Therefore, the
absorption, metabolism and distribution of these phenolic
acids could give credence to their therapeutic properties.
Conclusion
Caffeic acid and chlorogenic acid inhibited key enzymes
linked to Alzheimer’s disease (AChE and BChE) and some
pro-oxidants-induced lipid peroxidation in rat brain
in vitro. It could be concluded that some of the possible
mechanism by which they exert their neuroprotective
properties is by inhibiting AChE and BChE activities thus
slowing acetylcholine and butyrylcholine breakdown in the
brain as well as preventing oxidative neurodegeneration.
However, esterification of caffeic acid with quinic acid
producing chlorogenic acid reduces their neuroprotective
potential. However, this is an in vitro study with possible
physiological relevance.
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