Isolation and characterization of a monoamine oxidase inhibitor from tobacco leaves

Article abstract of DOI:10.1021/tx990146f

Recent positron emission tomography imaging studies have demonstrated a significant decrease in both monoamine oxidase A and B (MAO-A and MAO-B) activities in the brains of smokers. Normal levels of activity are observed in former smokers, suggesting the

Full text of DOI:10.1021/tx990146f

Chem. Res. Toxicol. 2000, 13, 31-35
31
Isola tion a n d Ch a r a cter iza tion of a Mon oa m in e Oxid a se
In h ibitor fr om Toba cco Lea ves
†
Ashraf A. Khalil, Salome Steyn, and Neal Castagnoli, J r.*
Department of Chemistry, Virginia Polytechnic Institute and State University,
Blacksburg, Virginia 24061-0212
Received August 3, 1999
Recent positron emission tomography imaging studies have demonstrated a significant
decrease in both monoamine oxidase A and B (MAO-A and MAO-B) activities in the brains of
smokers. Normal levels of activity are observed in former smokers, suggesting the presence of
one or more compounds in tobacco smoke that may inhibit these enzymes. In this paper, we
report the results of efforts to identify compounds present in flue-cured tobacco leaves that
inhibit MAO. The isolation procedure was guided by estimating the inhibitory properties of
tobacco leaf extracts on the liver mitochondrial MAO-B-catalyzed oxidation of 1-methyl-4-(1-
methylpyrrol-2-yl)-1,2,3,6-tetrahydropyridine to the corresponding dihydropyridinium metabo-
lite. Fractionation of extracts from flue-cured tobacco leaves led to the isolation of a competitive
inhibitor of human MAO-A (K
i
) 3 µM) and MAO-B (K ) 6 µM), the structure of which could
i
be assigned by classical spectroscopic analysis and confirmed by synthesis. This information
may help to provide insights into some aspects of the pharmacology and toxicology of tobacco
products.
In tr od u ction
smokers has been ruled out (16). The suggestion that
these effects may be caused by the 4-phenylpyridine and/
or hydrazine present in tobacco smoke (17) appears
unlikely since these compounds have no effects on MAO
activity or on dopamine levels in rodent brains (18).
We have initiated a systematic study to identify
compounds present in tobacco leaf extracts that inhibit
MAO. These studies have been aided by a robust spec-
The flavoenzymes monoamine oxidase A and B
MAO-A and MAO-B, respectively) catalyze the oxidative
1
(
deamination of the biogenic amine neurotransmitters and
a variety of xenobiotic amines (1). The development of
drugs which lead to the selective, reversible inhibition
of MAO-A is a subject of considerable interest since the
resulting increase in dopaminergic activity in the central
nervous system is thought to have antidepressant effects
trophotometric assay in which baboon liver mitochondrial
preparations2 were used as the enzyme source and
(
2). The selective inhibition of MAO-B also has been of
1
-methyl-4-(1-methylpyrrol-2-yl)-1,2,3,6-tetrahydropyri-
interest due to the reported neuroprotective properties
of (R)-deprenyl (3), a well-characterized and highly
selective mechanism-based inactivator of this form of the
enzyme (4) which is used to treat Parkinson’s disease (5).
Consequently, the recent findings that the activities of
both MAO-A (6) and MAO-B (7) are significantly reduced
in the brains of smokers have raised the possibility that
tobacco may contain a substance or substances with
antidepressant and/or neuroprotective properties. Anti-
depressant effects could contribute to the addiction
liability of tobacco, and neuroprotective effects could be
linked to the reported reduced risk that smokers have
for developing Parkinson’s disease (8-14).
dine (1) was used as the substrate (Scheme 1). The MAO-
generated metabolite, the 1-methyl-4-(1-methylpyrrol-2-
yl)-2,3-dihydropyridinium species 2, absorbs maximally
at 420 nm (19), which is distant from commonly encoun-
tered biological background absorbances. Since baboon
liver expresses essentially 100% MAO-B (20), this screen-
ing assay did not report on the MAO-A inhibiting
properties of the extracts. Studies on the inhibition of
human MAO-A employed the same substrate and mito-
chondria prepared from gastrointestinal mucosa which
3
expresses principally the A form of the enzyme. The
human liver mitochondria-catalyzed oxidation of the
MAO-B selective substrate 1-methyl-4-phenyl-1,2,3,6-
tetrahydropyridine (3) to the corresponding 1-methyl-4-
phenyl-2,3-dihydropyridinium metabolite 4 (λmax ) 343
nm) (21) was used to estimate the MAO-B inhibiting
properties of the active compound isolated from tobacco.
More than 2200 compounds have been identified in the
tobacco plant and/or in tobacco smoke (15). The possibility
that (S)-nicotine, the principal pharmacologically active
substance present in tobacco, may be responsible for the
lowered MAO-A and MAO-B activity in the brains of
Exp er im en ta l P r oced u r es
*
To whom correspondence should be addressed.
Current address: Department of Pharmaceutical Chemistry, Col-
†
Ca u tion : 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (3) is
a known nigrostriatal neurotoxin and should be handled using
disposable gloves in a properly ventilated hood.
lege of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451,
Saudi Arabia.
1
Abbreviations: GC/EIMS, gas chromatography/electron ionization
mass spectrometry; HMBC, homonuclear magnetic bond coordination;
HMQC, homonuclear magnetic quadrupole coordination; MAO, mono-
amine oxidase; SAR, structure-activity relationships; TIC, total ion
current.
2
The availability of large quantities of baboon liver mitochondria
(see ref 20) made this a convenient preparation for our screening
studies.
1
0.1021/tx990146f CCC: $19.00 © 2000 American Chemical Society
Published on Web 12/16/1999

3
2
Chem. Res. Toxicol., Vol. 13, No. 1, 2000
Khalil et al.
Sch em e 1. MAO-Ca ta lyzed Oxid a tion of th e
Sch em e 2. Syn th etic Rou te to
1
-Meth yl-4-a r yl-1,2,3,6-tetr a h yd r op yr id in yl
Su bstr a tes 1 a n d 3
2,3,6-Tr im eth yl-1,4-n a p h th oqu in on e (8)
Gen er a l Meth od s. Synthetic starting materials and analyti-
cal standards not described elsewhere were purchased from
Aldrich Chemical Co. (Milwaukee, WI). Enzyme grade mono and
dibasic sodium phosphate were obtained from Fisher Scientific
(
Pittsburgh, PA). Water was obtained from a Waters Milli-Q
chloroform (4 × 500 mL). The residue obtained after removing
the solvent (7.3 g) was chromatographed on silica gel (220 g)
using chloroform (1 L) followed by chloroform/methanol (9:1, 1
L). The most active fraction (fraction 2, 94 mg) was rechromato-
graphed on silica gel (10 g) using a gradient elution starting
with chloroform/hexane (70:30) and ending with pure chloro-
form. Fractions of 15 mL were collected. The most active
fraction, fraction 4 (15 mg), when subjected to preparative TLC
system (Milford, MA). The pyrrolyltetrahydropyridine 1 was
synthesized as described previously (19); the corresponding
phenyl analogue 3 was purchased from Research Biochemicals
Inc. (Natick, MA). The molar extinction coefficients of 24 000
M
1
-
1
-1
cm , for the dihydropyridinium metabolite 2 (19), and
-
1
-1
6 000 M cm , for the dihydropyridinium metabolite 4 (21),
are those reported in the cited literature. The human liver
sample was provided by F. P. Guengerich (Vanderbilt Univer-
sity, Nashville, TN) and the gastrointestinal mucosa by K.
Thummel (University of Washington, Seattle, WA). The tissues
were processed to yield mitochondrial fractions according to the
procedure described by Salach and Wyler (22). All protein
concentrations were determined by the method of Bradford (23).
NMR spectra were recorded on a Varian Unity NMR instrument
at 399.951 MHz for H and 100.578 MHz for C. Standard
Varian pulse sequence programs were used. Gas chromatogra-
phy/electron ionization mass spectrometry (GC/EIMS) was
performed on a Hewlett-Packard 5890 gas chromatograph fitted
with an HP-1 capillary column (15 m × 0.2 mm i.d., 0.33 mm
film thickness) which was coupled to a Hewlett-Packard 5870
mass selective detector. Data were acquired using an HP 5970
Chemstation. The GC-chemical ionization spectrum was ob-
tained on a CE-Fisons 8000 gas chromatograph coupled to a
VG Quattro mass spectrometer.
Bioa ssa y-Gu id ed F r a ction a tion of Toba cco Lea f Ex-
tr a cts. Shredded, flue-cured, and burley tobacco leaves were
kindly provided by Murty Pharmaceuticals (Lexington, KY).
Both types of tobacco (100 g) were stirred at room temperature
with hexane (2 × 1 L). The solid pack obtained after filtering
off the hexane was stirred with methanol (1 × 1 L) and, again
after filtration, with water (1 × 1 L). The assay used to monitor
the extracts was as follows. A mixture (500 µL, final volume)
composed of 0.1 M sodium phosphate buffer (pH 7.4, 350 µL),
the baboon liver mitochondrial preparation (25 µL, 3.0 mg of
protein/mL), 1-methyl-4-(1-methylpyrrol-2-yl)-1,2,3,6-tetrahy-
dropyridine (1) in 0.1 M sodium phosphate buffer (pH 7.4, 100
µL, 250 µM), and tobacco leaf extracts (25 µL containing final
concentrations of tobacco-derived materials ranging from 50 to
(500 µM neutral alumina and 40% hexane in chloroform) led to
the isolation of 2 mg of highly active material which, upon
rechromatography on neutral alumina, yielded 0.8 mg of a pure,
active compound.
2
,3,6-Tr im eth yl-1,4-n a p h th oqu in on e (8). All reactions
were monitored by GC/EIMS. A solution of 2,3-dimethyl-1,4-
benzoquinone (6, 1.0 g, 7 mmol), prepared by oxidation of 2,3-
dimethylphenol as described previously (24), and isoprene (0.57
g, 8.4 mmol) in ethanol (2 mL) was heated in a sealed vial at 80
1
13
°C for 3 h. The mixture was evaporated under reduced pressure
to yield 2,3,6-trimethyl-4a,5,8,8a-tetrahydro-1,4-naphthoqui-
none (7, Scheme 2). The crude tetrahydronaphthoquinone (1.1
g) was heated under reflux in xylene (30 mL) containing 10%
Pd/C (800 mg) for 7 h. The cooled reaction mixture was filtered,
the solvent removed, and the residue purified by passage
through a column of neutral Al
2 3
O (50 g) using a gradient elution
(
hexane to 30% CHCl in hexane). The fractions containing the
3
desired 2,3,6-trimethyl-1,4-naphthoquinone (8) were crystallized
from methanol to yield 0.75 g (51%) of pure 8: mp 97 °C [lit.
mp 103 °C (25)]. UV, IR, NMR, and GC/EIMS properties were
identical to those reported in ref 25.
Deter m in a tion of th e Mod e of In h ibition of MAO-B by
8. The human liver mitochondrial preparation (67 µL, 3 mg of
protein/mL) was incubated in 408 µL of 0.1 M sodium phosphate
buffer (pH 7.4) containing 25 µL of 1 mM 8 [final inhibitor
concentration of 50 µM in DMSO (5% final concentration); final
protein concentration of 3 mg/mL] for 0, 15, 30, and 60 min.
Each enzyme preparation was added at the specified time to a
mixture of 450 µL of 0.1 M sodium phosphate buffer (pH 7.4)
and 50 µL of 100 mM 3 (final substrate concentration of 5 mM)
which had been pre-equilibrated to 37 °C. The resulting
mixtures were incubated for 45 min with gentle agitation in a
water bath at 37 °C and workup as described above for the
screening assay. The concentration of the dihydropyridinium
metabolite (4) was estimated at λmax ) 343 nm by scanning the
supernatant from 600 to 250 nm.
2
00 µg/mL based on the stage of purification) in DMSO (final
concentration of DMSO held constant at 5%) was incubated with
gentle agitation in a water bath at 37 °C for 30 min. A solution
of 70% aqueous HClO (20 µL) then was added, and the resulting
4
mixture was vortex agitated. The denatured protein was sedi-
mented at 14 000 rpm for 5 min, and the supernatant was
scanned from 600 to 250 nm on a Beckman DU-7400 spectro-
photometer. The absorbance at 420 nm was used to estimate
the concentration of 2.
Subsequently, 1 kg of flue-cured tobacco was extracted with
hexane (3 × 2 L), and after being concentrated to a final volume
of 500 mL, the hexane extract was partitioned with 80% aqueous
methanol (3 × 1 L). The aqueous methanol fraction, which
contained the majority of the activity, was diluted with water
In h ibition of Hu m a n Liver Mitoch on d r ia l MAO-B a n d
Hu m a n Ga str oin testin a l Mitoch on d r ia l MAO-A by 8. All
kinetic studies were performed in duplicate, and the resulting
values varied by less than 5%.
Due to the limited solubility of the naphthoquinone in
aqueous solutions, methanol was used as a cosolvent. The final
methanol concentration in all incubations was kept at 4%. It
was necessary to evaluate the effects of methanol on the Km
values for the substrate molecules before starting the inhibition
studies. In the case of the MAO-B selective substrate 3, an
aliquot of the human liver mitochondrial preparation was
(
500 mL), and the active components were extracted into
3
The characterization of the MAO activity present in human
gastrointestinal mucosa will be reported separately.
-
8
preincubated with 10 M clorgyline at 37 °C for 15 min. This

MAO Inhibitors from Tobacco
Chem. Res. Toxicol., Vol. 13, No. 1, 2000 33
preparation (25 µL, 12 mg of protein/mL) was added to a mixture
consisting of 0.1 M sodium phosphate buffer (pH 7.4, 355 µL)
and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (3) in 0.1 M
sodium phosphate buffer (pH 7.4, 100 µL) to yield final
concentrations of 40, 80, 160, 240, 320, and 640 µM. These
mixtures were incubated for 15 min with gentle agitation in a
water bath at 37 °C and worked up as described for the
screening assay. The absorbance at 343 nm was used to estimate
the concentration of the dihydropyridinium metabolite (4). The
K
m
value (-1/x when y ) 0) for 3 was determined from the
double-reciprocal plot of 1/(rate of formation of 4) (i.e., 1/V)
versus 1/[3]. The inhibition studies of the effect of 8 on MAO-B
activity were performed following the procedure described above
except in the presence of varying final concentrations of 8 (0, 4,
F igu r e 1. GC/EIMS TIC chromatogram of the active fraction.
8
, 16, and 32 µM). The final methanol concentration was kept
at 4%. The K value (-x when y ) 0) was estimated from the
i
replot in which the values of the slopes obtained from the
double-reciprocal plots of 1/V versus 1/[S] with increasing
concentrations of 8 are plotted against the concentration of 8
(see Figure 6).
A parallel study was conducted with mitochondria prepared
from human gastrointestinal mucosa using the pyrrolyl sub-
strate 1. The good MAO-B substrate properties of 1 (19) required
that this form of the enzyme be inactivated prior to examining
the effects of 8 on the MAO-A-catalyzed oxidation of 1. The
-
7
mitochondria, therefore, were preincubated with 3 × 10
M
4
(
R)-deprenyl for 15 min to inactivate MAO-B. The K
m
value
for 1 (10, 20, 40, 60, 80, and 160 µM) in the presence of 4%
methanol was determined from the same type of study described
above for human liver mitochondrial MAO-B. The MAO-B-
inactivated preparations were then examined as described above
F igu r e 2. GC/EIMS TIC chromatogram of fraction 2.
to estimate the K
naphthoquinone 8 using the same type of replot described above
see Figure 6).
i
value for the inhibition of MAO-A by the
(
Resu lts a n d Discu ssion
Isola tion a n d Str u ctu r e An a lysis. The fractionation
procedure was based on the partitioning of the tobacco
leaf components between polar and nonpolar solvents to
avoid loss of activity due to exposure to acids and bases.
It should be noted that activity (as measured by the rate
of oxidation of the pyrrolyltetrahydropyridine substrate
1
by baboon liver mitochondria) did not localize in one
F igu r e 3. GC/EIMS TIC chromatogram of fraction 3.
fraction. Consequently, more than one compound may be
present in the tobacco plant with MAO inhibiting proper-
ties. Results from the initial partitioning experiments
demonstrated that the components of interest were
lipophilic in nature since activity could be extracted from
the plant into hexane but not into water. Alkaloid-type
structures that should react with Dragendorff’s reagent
were not present in this hexane extract.
A series of liquid-liquid partitionings led to the
isolation of 7 g of active material (200 µg/mL resulting
in 23% inhibition) that subsequently was subjected to
column chromatography on silica gel to yield 94 mg (200
µg/mL resulting in 71% inhibition). The total ion current
(
TIC) chromatogram of this fraction obtained by GC/
F igu r e 4. GC-EI mass spectrum of the peak eluting at 11.15
min.
EIMS is shown in Figure 1.
The complexity of this tracing led us to rechromato-
graph this material on a column of silica gel, which led
to a 2-fold increase in activity. Preparative silica gel TLC
of this material (15 mg) gave 11 fractions, two of which
3
inhibited MAO-B activity (50 µg/mL resulting in 87%
inhibition) about 4 times more effectively than did
fraction 2. The same 4:1 ratio was observed for the peak
eluting at 11.14 min in the two chromatograms. The
arrow in Figure 1 indicates the retention time corre-
sponding to this peak in the more crude isolate.
[fraction 2 (2 mg) and fraction 3 (4 mg)] exhibited similar
GC-TIC reacings (Figures 2 and 3, respectively). Fraction
The EI mass spectrum of this peak (Figure 4) indicated
the presence of a single compound with a molecular mass
of 200 Da. The corresponding GC-chemical ionization
4
The reader is referred to our recent publication (20) that describes
how the conditions for selectively inhibiting MAO-B activity were
established.

3
4
Chem. Res. Toxicol., Vol. 13, No. 1, 2000
Khalil et al.
F igu r e 5. 13C NMR chemical shift assignments (parts per
million) of compound 8. The asterisks denote interchangeable
assignments.
+
mass spectrum (not shown) gave a parent ion (MH ) at
m/z 201, confirming the molecular mass assignment. An
MS library search (Wiley library) resulted in 20 hits, one
of which [2,3,6-trimethyl-1,4-naphthoquinone (8)] had a
fragmentation pattern essentially identical to that of the
isolate. A literature search established that this naph-
thoquinone is present in tobacco smoke (26, 27). However,
this would be the first report of the presence of 8 in the
tobacco plant itself.
The synthesis of 8 was pursued in an effort to confirm
this assignment and to provide larger quantities for
biological studies. Older synthetic routes to 8 were
unattractive. The first reported synthetic pathway is
based on the oxidation of 2,3,6-trimethylnaphthalene that
was derived from the fractional distillation of petroleum
(28). The second route includes oxidation of the com-
mercially available 2,6-dimethylnaphthalene followed by
the introduction of the C-3 methyl group with dia-
zomethane, a low-yield reaction (29). Our approach
proceeded via 2,3-dimethylbenzoquinone (6) which was
obtained by oxidation of commercially available 2,3-
dimethylphenol (5) (24). Reaction of 6 with isoprene in a
sealed vial gave the Diels-Alder adduct 7 which under-
went dehydrogenation when heated in the presence of
Pd/C to yield 8. GC/EIMS and TLC analyses established
that synthetic 8 and the product isolated from the tobacco
plant were identical. Because of our interest in conduct-
ing SAR studies, the structure of 8 was fully character-
F igu r e 6. Double-reciprocal (1/V vs 1/[S]) plots of the rates of
formation of the dihydropyridinium species 2 with varying
concentrations of substrate 1 carried out in the presence of
varying concentrations of inhibitor 8. The insets are the replots
of the slopes vs inhibitor concentrations (K ) -x when y ) 0).
i
Panel A depicts data for the human gastrointestinal MAO-A-
catalyzed oxidation of 1-methyl-4-(1-methyl-2-pyrrolyl)-1,2,3,6-
tetrahydropyridine (1), while panel B depicts the data for the
human liver MAO-B-catalyzed oxidation of 1-methyl-4-phenyl-
1,2,3,6-tetrahydropyridine (3).
ized by NMR spectroscopy. The assignments of the 13
C
NMR chemical shifts (Figure 5) were achieved with the
aid of two-dimensional NMR (HMQC and HMBC).
En zym e Stu d ies. The MAO-B inhibiting properties
of 8 observed in the baboon liver mitochondrial assay
were qualitative in nature only. More quantitative stud-
ies on the interactions of synthetic 8 with both MAO-A
and MAO-B were pursued with human enzymes. The
effect of the MAO-B inhibitory properties of 8 on the
oxidation of the tetrahydropyridine 3 was investigated
first as a function of time to determine if 8 was a time-
dependent inactivator of MAO-B. When the human liver
mitochondrial preparation was preincubated with 8 (50
µM) for 0, 15, 30, and 60 min, the rate of MAO-B-
catalyzed oxidation of 3 (5 mM) was unchanged. These
studies established that the MAO-B catalytic activity of
the human liver mitochondria was stable over time and
that the inhibitory properties of 8 were not time-depend-
ent.
K
K
i
values for the inhibition of these enzymes by 8. The
value was for the oxidation of 1 by human gas-
m
trointestinal mitochondrial MAO-A in the presence of
-
7
1
0
M (R)-deprenyl was estimated to be 34 µM from the
plot of the reciprocal of the velocities of this reaction
versus the reciprocal of the substrate concentrations. A
similar analysis of the oxidation of 3 by human liver
mitochondrial MAO-B in the presence of 10 M clor-
gyline gave a K value of 128 µM.
-
8
m
The extent of inhibition of these reactions by various
concentrations of 8 (4, 8, 16, and 32 µM) was examined
at substrate concentrations that bracketed the above K
m
values. Figure 6A shows the double-reciprocal plots for
the oxidation of 1 by human gastrointestinal mitochon-
dria in the presence of varying concentrations of 8. This
is a classical plot for a competitive inhibitor (30). The
secondary plot of the slopes of the lines against the
concentration of 8 (see the inset) provided an estimate
for K
A similar study gave a K
by 8 of the oxidation of 3 by human liver mitochondrial
The human gastrointestinal mitochondrial MAO-A-
catalyzed oxidation of the pyrrolyl substrate 1 and the
human liver mitochondrial MAO-B-catalyzed oxidation
of the phenyl substrate 3 were employed to estimate the
i
of 3 µM (intercept of the x-axis with the y origin).
i
value of 6 µM for the inhibition

MAO Inhibitors from Tobacco
Chem. Res. Toxicol., Vol. 13, No. 1, 2000 35
MAO-B (Figure 6B). The straight lines in the double-
reciprocal plots for MAO-A and -B (panels A and B of
Figure 6, respectively) show common intersections above
the x-axis which suggests that this inhibition is competi-
tive rather than noncompetitive (intersection on the
x-axis) or uncompetitive (parallel lines). On the basis of
these values, the purification factor starting from the
active fraction (7 g isolated from 1000 g of tobacco) can
be estimated to be 500-fold.
The potential biological significance of these findings
is being studied. We are particularly interested in
determining the in vivo activities of 8 on the activities of
brain MAO-A and MAO-B. A positive finding from these
experiments may provide useful information about the
effects of smoking on human behavior and a possible
rationale for helping to explain the lowered risk of
smokers to developing Parkinson’s disease.
Biophys. Res. Commun. 222, 607-611.
(
10) Morens, D. M., Grandineti, A., Reed, D., White, L. R., and Ross,
G. W. (1995) Cigarette smoking and protection from Parkinson’s
disease: False association or etiologic clue? Neurology 45, 1041-
1051.
(11) Carr, L. A., and Rowell, P. P. (1990) Attenuation of 1-methyl-4-
phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity by to-
bacco smoke. Neuropharmacology 29, 311-314.
12) Yu, P. H., and Boulton, A. A. (1987) Irreversible inhibition of
monoamine oxidase by some components of cigarette smoke. Life
Sci. 41, 675-682.
13) Baron, J . A. (1986) Cigarette smoking and Parkinson’s disease.
Neurology 36, 1490-1496.
14) Oreland, L., Fowler, C. J ., and Schalling, D. (1981) Low platelet
monoamine oxidase activity in cigarette smokers. Life Sci. 29,
2511-2518.
15) Schmeltz, I., and Hoffmann, D. (1977) Nitrogen-containing com-
pounds in tobacco and tobacco smoke. Chem. Rev. 77, 295-311.
16) Fowler, J . S., Volkow, N. D., Logan, J ., Pappas, N., King, P.,
MacGregor, R., Shea, C., Garza, V., and Gatley, S. J . (1998) An
acute dose of nicotine does not inhibit MAO B in baboon brain in
vivo. Life Sci. 63, 19-23.
(
(
(
(
(
(
17) Yong, V. W., and Perry, T. L. (1986) Monoamine oxidase B,
smoking, and Parkinson’s disease. J . Neurol. Sci. 72, 265-272.
18) Carr, L. A., and Basham, K. (1991) Effects of tobacco smoke
constituents on MPTP-induced toxicity and monoamine oxidase
activity in the mouse brain. Life Sci. 48, 1173-1177.
Ack n ow led gm en t. This work was supported by a
grant from the National Institute on Drug Abuse
DA11089), a gift from Reverend Stewart Bryan West,
and the Harvey W. Peters Center for the Study of
Parkinson’s Disease, Department of Chemistry, Virginia
Polytechnic Institute and State University.
(
(
(19) Nimkar, S. K., Anderson, A., Rimoldi, J . M., Stanton, M.,
Castagnoli, K. P., Mabic, S., Wang, Y.-X., and Castagnoli, N., J r.
(1996) Synthesis and monoamine oxidase-B catalyzed oxidation
of C-4 heteroaromatic substituted 1,2,3,6-tetrahydropyridine
derivatives. Chem. Res. Toxicol. 9, 1013-1022.
Refer en ces
(
20) Inoue, H., Castagnoli, K., Van der Schyf, C., St e´ phane, M.,
Igarashi, K., and Castagnoli, N., J r. (1999) Species dependent
differences in the monoamine oxidase A and B catalyzed oxidation
of various C-4 substituted 1-methyl-4-phenyl-1,2,3,6-tetrahydro-
pyridinyl derivatives. J . Pharmacol. Exp. Ther. 291, 856-864.
21) Chiba, K., Peterson, L. A., Castagnoli, K. P., Trevor, A. J ., and
Castagnoli, N., J r. (1985) Studies on the molecular mechanism
of bioactivation of the selective nigrostriatal toxin 1-methyl-4-
phenyl-1,2,3,6-tetrahydropyridine (MPTP). Drug Metab. Dispos.
(
1) Dostert, P., Strolin-Benedetti, M., and Tipton, K. F. (1989)
Interactions of monoamine oxidase with substrates and inhibitors.
Med. Res. Rev. 9, 45-89.
2) Kato, M., Katayama, T., Iwata, H., Yamamura, M., Matsuoka,
Y., and Nariat, H. (1998) In vivo characterization of T-794, a novel
reversible inhibitor of monoamine oxidase-A, as an antidepressant
with a wide safety margin. J . Pharmacol. Exp. Ther. 284, 983-
(
(
9
90.
(
3) Magyar, K., Szende, B., Lengyel, J ., Tarczali, J ., and Szatmary,
I. (1998) The neuroprotective and neuronal rescue effects of
1
3, 342-347.
(
(
(
(
22) Salach, J . I., and Weyler, W. (1987) Preparation of the flavin-
containing aromatic amine oxidases of human placenta and beef
liver. Methods Enzymol. 142, 627-637.
23) Bradford, M. M. (1976) A rapid and sensitive method for the
quantitation of microgram quantities of protein utilizing the
principle of protein-dye binding. Anal. Biochem. 72, 248-254.
24) Norris, R. K., and Sternhell, S. (1966) Long-range spin-spin
coupling in 1,4-benzoquinones and some related compounds. Aust.
J . Chem. 19, 617-627.
25) Thomson, R. H. (1987) in Naturally Occurring Quinones, III,
Recent Advances, pp 127-130, Chapman and Hall, London.
(26) Chamberlain, W. J ., and Stedman, R. L. (1968) Composition
studies on tobacco. XXVIII. 2,3,6-Trimethyl-1,4-naphthoquinone
in cigarette smoke. Phytochemistry 7, 1201-1203.
(
-)-deprenyl. J . Neural Transm., Suppl. 52, 109-123.
(
4) Borbe, H. O., Niebch, G., and Nickel, B. (1990) Kinetic evaluation
of MAO-B activity following oral administration of selegiline and
desmethylselegiline in the rat. J . Neural Transm., Suppl. 32,
1
31-137.
5) Findley, L. J . (1995) Selective Monoamine Oxidase-B inhibitor
Deprenyl) in Parkinson’s Disease. In Therapy of Parkinson’s
(
(
(
(
(
Disease (Koller, W. C., and Paulson, G., Eds.) pp 311-319, Marcel
Dekker, New York.
6) Fowler, J . S., Volkow, N. D., Wang, G. J ., Pappas, N., Logan, J .,
Shea, C., Alexoff, D., MacGregor, R., Schlyer, D., Zezulkova, I.,
and Wolf, A. P. (1996) Brain monoamine oxidase A inhibition in
cigarette smokers. Proc. Natl. Acad. Sci. U.S.A. 93, 14065-14069.
7) Fowler, J . S., Volkow, N. D., Wang, G. J ., Pappas, N., Logan, J .,
MacGregor, R., Alexoff, D., Shea, C., Schlyer, D., and Wolf, A. P.
(27) Kimland, B., Appleton, A. J ., Aasen, A. J ., Roseraade, J ., and
Enzell, C. R. (1972) Neutral oxygen-containing volatile constitu-
ents of Greek tobacco. Phytochemistry 11, 309-316.
(
1996) Inhibition of monoamine oxidase B in the brains of
smokers. Nature 379, 733-736.
8) Soto-Otero, R., Mendez-Alvarez, E., Riguera-Vega, R., Quinoa-
Cabana, E., Sanchez-Sellero, I., and Lopez-Rivadulla, L. M. (1998)
Studies on the interaction between 1,2,3,4-tetrahydro-â-carboline
and cigarette smoke: a potential mechanism of neuroprotection
for Parkinson’s disease. Brain Res. 802, 155-162.
(28) Kruber, O. (1939) U¨ ber die Trimethylnaphthaline im Steinkon-
lenteer. Chem. Ber. 72, 1972-1977.
(29) Bergmann, E., and Bergmann, F. (1938) Synthesis and reactions
of substituted R-naphthoquinones J . Org. Chem. 3, 125-136.
(
30) Copeland, R. A. (1996) Reversible Inhibitors. In Enzymes. A
Practical Introduction to Structure, Mechanism, and Data Analy-
sis, pp 187-223, VCH Publishers, New York.
(9) Soto-Otero, R., Riguera-Vega, R., Mendez-Alvarez, E., Sanchez-
Sellero, I., and Lopez-Rivadulla, L. M. (1996) Interaction of
1
,2,3,4-tetrahydroisoquinoline with some components of cigarette
smoke: potential implications for Parkinson’s disease. Biochem.
TX990146F