International
Journal
of
Pharmaceutics
425 (2012) 29–
34
Contents
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at
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International
Journal
of
Pharmaceutics
jo
ur
nal
homep
a
ge:
www.elsevier.com/locate/ijpharm
Montmorillonite
intercalated
with
glutathione
for
antioxidant
delivery:
Synthesis,
characterization,
and
bioavailability
evaluation
Miri
Baek
a
,
Jin-Ho
Choy
b,∗
,
Soo-Jin
Choi
a,∗∗
a
Department
of
Food
Science
and
Technology,
Seoul
Women’s
University,
Seoul
139-774,
Republic
of
Korea
b
Center
for
Intelligent
Nano-Bio
Materials,
Department
of
Chemistry
and
Nano
Science,
Department
of
Bioinspired
Science,
Ewha
Womans
University,
Seoul
120-750,
Republic
of
Korea
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
2
November
2011
Received
in
revised
form
12
December
2011
Accepted
7
January
2012
Available online 14 January 2012
Keywords:
Glutathione
Montmorillonite
Antioxidant
activity
Pharmacokinetics
Tissue
distribution
a
b
s
t
r
a
c
t
A
most
powerful
antioxidant,
glutathione
(GSH),
plays
an
important
role
in
detoxification,
immune
response,
and
protection
against
reactive
oxygen
species.
However,
orally
ingested
GSH
can
be
easily
degradable
to
free
amino
acids
by
chemical
and
enzymatic
hydrolysis,
resulting
in
low
bioavailability.
The
aim
of
this
study
was,
therefore,
to
enhance
GSH
bioavailability
by
developing
GSH–montmorillonite
(MMT)
hybrid
system.
It
was
also
coated
with
polyvinylacetal
diethylaminoacetate
(AEA)
for
better
stabil-
ity.
Both
GSH–MMT
and
AEA–GSH–MMT
hybrids
were
characterized
by
powder
X-ray
diffraction
(PXRD),
Fourier
transformed
infrared
(FT-IR),
and
thermogravimetric
analysis
(TGA),
indicating
that
GSH
was
suc-
cessfully
intercalated
into
the
interlayer
spaces
of
MMT.
In
vivo
antioxidant
activity
assay
revealed
that
AEA–GSH–MMT
hybrid
significantly
increased
antioxidant
activity
in
the
plasma
after
oral
administra-
tion
in
mice.
Pharmacokinetic
study
also
indicated
that
AEA–GSH–MMT
hybrid
considerably
increased
the
plasma
concentration
of
GSH
at
1
h
post-oral
administration.
Moreover,
both
the
hybrid
systems
remarkably
enhanced
GSH
delivery
to
the
main
target
tissue,
liver.
All
the
results
suggest
that
GSH–MMT
hybrid
systems
have
great
potential
to
enhance
bioavailability
of
oral
GSH,
providing
new
insight
into
their
pharmaceutical
application.
© 2012 Elsevier B.V. All rights reserved.
1.
Introduction
Glutathione
(␥-l-glutamyl-l-cysteinylglycine,GSH)
is
a
water-
soluble
tripeptide
involved
in
many
biological
processes
including
intermediary
metabolism,
catalysis,
and
transport
(Bannai
and
Tateishi,
1986).
It
also
acts
as
an
endogenous
antioxidant,
playing
an
important
role
in
the
protection
of
cells
against
reactive
oxygen
species
by
neutralizing
free
radicals
(Brezeninska-Slebodzinska
et
al.,
1995;
Milne
et
al.,
1993).
Thus,
it
is
known
that
high
con-
centration
of
GSH
is
found
in
the
organs
frequently
exposed
to
xenobiotics
such
as
liver,
kidney,
and
intestine
(Jewell
and
O’Brien,
1999).
In
addition,
GSH
is
essential
to
maintain
the
normal
function
of
the
immune
system
as
an
immune
booster,
for
example,
by
activating
lymphocytes
(Li
et
al.,
2007).
Therefore,
systemic
GSH
and
cysteine
depletion
have
occurred
in
many
diseases
such
as
HIV
infection,
acute
respiratory
disease,
and
Parkinson’s
disease
(Mihm
et
al.,
1991;
Jahoor
et
al.,
1999).
However,
orally
ingested
GSH
can
be
easily
degraded
to
free
amino
acids
by
chemical
and
enzymatic
hydrolysis
(Witschi
et
al.,
1992).
Oral
GSH
is
hydrolyzed
∗
Corresponding
author.
Tel.:
+82
2
3277
4135;
fax:
+82
2
3277
4340.
∗∗
Corresponding
author.
Tel.:
+82
2
970
5634;
fax:
+82
2
970
5977.
E-mail
addresses:
jhchoy@ewha.ac.kr
(J.-H.
Choy),
sjchoi@swu.ac.kr
(S.-J.
Choi).
in
the
intestine
by
the
intestinal
gamma-glutamyl
transferase,
so
small
amount
of
GSH
reaches
the
portal
circulation
from
the
small
intestine
during
gastrointestinal
(GI)
transit
(Anderson
et
al.,
1980).
If
any,
it
is
also
rapidly
metabolized
by
hepatic
gamma-glutamyl
transferase,
eventually
resulting
in
low
absorption
rate
into
the
blood
circulation
and
low
bioavailability
in
the
tissues
(Shaw
and
Newman,
1979).
Moreover,
GSH
with
a
thiol
group
can
be
easily
oxidized
both
enzymatically
and
non-enzymatically
at
alkaline
pH
such
as
intestinal
environment,
giving
rise
to
the
formation
of
glu-
tathione
disulphide
(GSSG),
which
is
devoid
of
antioxidant
activity
(Aw,
2005).
In
this
regard,
the
development
of
novel
delivery
carrier
systems
can
be
useful
to
stabilize
and
protect
labile
GSH
against
harsh
biological
conditions,
subsequently
leading
to
increase
its
bioavailability
following
oral
ingestion.
A
few
attempts
have
been
made
to
develop
GSH
delivery
systems,
and
to
the
best
of
our
knowledge,
no
study
has
clearly
demonstrated
the
efficacy
of
GSH
delivery
systems
in
vivo
(Aisawa
et
al.,
2006;
Trapani
et
al.,
2007).
Montmorillonite
(MMT),
a
natural
clay
mineral,
is
a
bio-
inspired
layered
material
with
high
internal
surface
area,
high
cation
exchange
capacity
(CEC),
high
adsorption
ability,
and
low
toxicity
(Lee
and
Fu,
2003;
Komine,
2004).
MMT
with
net
negatively
charge
layers
has
good
swelling
property
in
the
presence
of
water,
and
therefore,
the
positively
charged
bioactive
compounds
can
be
intercalated
into
the
interlayer
spaces
by
electrostatic
interaction
0378-5173/$
–
see
front
matter ©
2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.ijpharm.2012.01.015