Synthesis and characterization of new amino acid-schiff bases and studies their effects on the activity of ACP, PAP and NPA enzymes (In Vitro)

Article abstract of DOI:10.1155/2012/218675

In this study, two new Schiff base compounds derived from the condensation reaction of L-glycine and L-tryptophan with 4-methylbenzal-dehyde have been synthesized. The Schiff base compounds were characterized by FT-IR, UV and ¹H NMR spectroscopy. Their effects on the activity of total (ACP), prostatic (PAP) and non prostatic (NPA) acid phosphatase enzymes were studied. The Schiff base derived from L-glycine (A) demonstrated inhibition effect on the ACP and NPA activities and activation effect on PAP activity. The Schiff base derived from L-tryptophan (B) demonstrated semi fixed inhibition effects on the ACP and NPA activities at high concentrations (5.5×10^-2, 5.5×10^-3 and 5.5×10^-4 M) and activator effect at low concentration (5.5×10^-5 M) while it was exhibits as activator on PAP activity.

Full text of DOI:10.1155/2012/218675

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
http://www.ejchem.net
2012, 9(2), 962-969
Synthesis and Characterization of New Amino
Acid-Schiff Bases and Studies their Effects on the
Activity of ACP, PAP and NPA Enzymes (In Vitro)
ZAHRAA SALIM M. AL-GARAWI,
IVAN HAMEED R. TOMI and ALI HUSSEIN R. AL-DARAJI
Department of Chemistry, College of Sciences
University of Al-Mustansiriya, Baghdad, Iraq
ivanhrtomy@yahoo.com
Received 17 October 2011; Accepted 30 December 2011
Abstract: In this study, two new Schiff base compounds derived from the
condensation reaction of L-glycine and L-tryptophan with 4-methylbenzal-
dehyde have been synthesized. The Schiff base compounds were characterized
by FT-IR, UV and 1H NMR spectroscopy. Their effects on the activity of total
(ACP), prostatic (PAP) and non prostatic (NPA) acid phosphatase enzymes
were studied. The Schiff base derived from L-glycine (A) demonstrated
inhibition effect on the ACP and NPA activities and activation effect on PAP
activity. The Schiff base derived from L-tryptophan (B) demonstrated semi
fixed inhibition effects on the ACP and NPA activities at high concentrations
(5.5×10-2, 5.5×10-3 and 5.5×10-4 M) and activator effect at low concentration
(5.5×10-5 M) while it was exhibits as activator on PAP activity.
Introduction
Schiff bases are the compounds containing azomethin group (-HC=N-). They are
condensation products of ketones or aldehydes with primary amines. Formation of Schiff
base generally takes place under acid or base catalysis or with heat. Schiff-bases are
considered as a very important class of organic compounds and have a wide application in
many biological aspects, proteins, visual pigments, enzymatic aldolization and
decarboxylation reactions1. Moreover, some Schiff-bases were exhibits antibiotic, antiviral
and antitumor agents because of their specific structure2.
Acid phosphatase (ACP) is a type of enzyme manufactured by the body. It is classified
as a hydrolase enzyme. Specifically, acid phosphatase targets and breaks the molecular
bonds of phosphate groups3. Generally speaking, ACP can be found in certain organs and tissues,
including blood cells, bone marrow, spleen, pancreas, liver, and kidneys4. However, this
substance is found in the greatest concentration in the prostate and up to 1,000 times greater
in seminal fluid than any other bodily fluids. Prostatic acid phosphatase (PAP) is an enzyme

Synthesis and Characterization of New Amino Acid-Schiff Bases 369
produced by the prostate. Its evaluated in prostate cancer. The highest levels of acid
phosphatase are found in metastasized prostate cancer, while diseases of the bone, such as
Paget's disease or hyperparathyroidism, diseases of blood cells, such as sickle-cell disease or
multiple myeloma or lysosomal storage diseases, such as Gaucher's disease, will show
moderately increased levels5.
Schiff bases appear to be an important intermediate in a number of enzymatic reactions
involving interaction of an enzyme with an amino or a carbonyl group of the substrate. One
of the most important types of catalytic mechanism is the biochemical process which
involves the condensation of a primary amine in an enzyme usually that of a lysine residue,
with a carbonyl group of the substrate to form an imine, or Schiff base6.
There are many interesting studies on the Schiff bases compounds derived from amino
acids. Matharasi et al7 found that the Schiff bases derived from amino acid and Aloin [the
bio active molecule, 10-glucopyranosyl-1,8-dihydroxy-3-(hydroxylmethyl)-9, (10H)
anthracenone] having good antibacterial activity in good range when comparison to control
(Ampicilin). Also Deng et al8 synthesized a new derivative of amino acids azomethin and its
complexes with tin that it used in biological activates. The 2-acetyl-benzimidazoledehyde-
glycine Schiff base ligand and the corresponding Pr (III) complexes were synthesized and
their fluorescent properties studied by Danghui et al9. Also, the Schiff bases compounds
derived from amino acids were used as a ligands and their complexes were used in wide
range in medicinal chemistry10-12
.
The aim of the present work is to studying the effect of Schiff base compounds derived
from L-glycine and L-tryptophan on the activity of acid phosphatase enzymes, where no
similar researches found in the literature. These products might be potential compounds for
biological activity tests on this enzyme.
Experimental
All starting materials and solvents were purchased from Aldrich and Fluka and used without
further purification. Melting points were determined on Electrothermal capillary apparatus and
1
are uncorrected, FT-IR measurements were recorded on Shimadzu model FTIR-8400S. H
NMR spectra were obtained with Bruker spectrophotometer model ultra shield at 300 MHz in
DMSO-d6 solution with the TMS as internal standard. UV–Vis spectra and the enzyme activity
for the compounds were measured at room temperature by using (UV–Vis) spectrophotometer
type Shimadzu. Acid phosphatase kit (total and prostatic) was made in Linear chemicals S. L.
company (kinetic method type) Note: in some 1H NMR spectra, the peaks at δ 2.5 and 3.35 are
for the solvent (DMSO-d6) and dissolved water in (DMSO-d6) respectively.
Preparation method of amino acids Schiff bases A & B
The Schiff bases derived from 4-methylbenzaldehyde and L-amino acids were prepared
using a method similar to one given in the reference13. To a solution of 4-methylbenzal-
dehyde (0.144 g, 1.2 mmol) in methanol (10 mL), L-amino acid (1.0 mmol) in methanol
(15 mL) containing potassium hydroxide (0.056 g, 1.0 mmol) was added. The obtained
solution was then magnetically stirred for 8 h at 50 - 60oC in water bath. The volume of the
obtained brownish red solution was reduced in vacuum using a rotary evaporator and then
washed with absolute ethanol. Anhydrous diethyl ether was added to wash the products at
room temperature and then dried in air for 2 h. The physical properties and FT-IR data for
1
Schiff bases derivatives are listed in Table 1. H NMR (A): (DMSO-d6, 300 MHz, δ, ppm)
11.23, 8.11, 6.88-7.90, 2.33, 2.05; (B): (DMSO-d6, 300 MHz, δ, ppm) 11.34, 8.03, 6.73-
7.91, 3.09, 2.31, 2.02.

369 IVAN HAMEED R. TOMI et al.
Table 1. Physical, FT-IR and electronic spectral data of compounds A and B.
Physical properties
FT-IR spectral data
Electronic
data,
λmax/nm
Comp.
Empirical Yield Mp,
υ
υ C-H
aliph
2949,
2850
2056,
2862
υ O-H υ C=C
υ C=O
formula
%
oC
*
CH=N
1587,
1514
1589,
1515
A
B
C10H11NO2 70
C19H18N2O2 77
3256
1652 1707
1641 1709
256, 212
258, 220
88-90 3259
Materials and methods of biological activity section
The method14,15 is based on the hydrolysis of α-naphtyl phosphate at pH 5.2 by acid
phosphatase (ACP) to produce α-naphtol and inorganic phosphate. The pentanediol acts as
phosphate acceptor increasing the reaction sensitivity.
The α-naphtol reacts with fast Red TR, to produce a coloured complex directly
proportional to the activity of ACP in the sample. α-naphthylphosphate is hydrolyzed by
serum acid phosphatase to a-napthol and inorganic phosphate. The rate of hydrolysis is
proportional to the enzyme acitivity present. The α-naphthol produced is coupled with Fast
Red TR to produce a colored complex which absorbs light at 405 nm. The reaction can be
quantitated photometrically because the coupling reaction is instantaneous. L-Tartrate
inhibits prostatic acid phosphatase but does not interfere with the reaction mechanism.
Therefore, if testing is performed in the presence and in the absence of L-Tartrate, the
difference between the results of the two assays is the level of prostatic acid phosphatase in
the serum.
ACP
α-naphtyl phosphate
+
H2O
α-naphtol
+ Pi
pH 5.0
α-naphtol + Fast Red TR
Azo dye
30-37 oC
A stock solution (5.5 mmol) of compounds A and B were prepared by dissolving these
compounds in buffer solution of ACP kit (Sodium citrate 110 mmol/L, 1,5-pentanediol
220 mmol/L, pH 5.2) and the following concentrations (5.5×10-2, 5.5×10-3, 5.5×10-4, 5.5×10-5
mmol) were prepared by diluting with the same buffer. The ACP and NPA activities of a
healthy subject (21 years old) were determined. The inhibition and activation percentage
were calculated by comparing the activity with and without the Schiff base compounds
under the same enzymatic reaction by replacing 100 μL of buffer with 100 μL of A and B
solutions, according to the equation:
% Inhibition = 100 – 100 × (The activity in the presence of inhibitor) / (The activity in
the absence of inhibitor). The activation percentage was calculated by comparing the activity
with and without the activator and under the same conditions, according to the equation: %
Activation = 100 × (The activity in the presence of activator) / (The activity in the absence
of activator) – 100. The activity of PAP enzyme was calculated by the following equation:
Activity of PAP enzyme = activity of ACP enzyme – activity of NPA enzyme
Results and Discussion
Synthesis
The condensation of 4-methylbenzaldehyde and L-amino acids in methanol gives the
products A and B according to the following reaction:

Synthesis and Characterization of New Amino Acid-Schiff Bases 369
H
C
R
O
C
H2N
COOH
H3C
H
+
KOH
Methanol
Reflux 8 h
H
C
R
H3C
C
H
N
COOH
R =
R =
H
compound A
H2
C
compound B
NH
The physical, FT-IR and electronic spectral data of these compounds are listed in
Table 1. These compounds are soluble in methanol, ethanol and other polar solvents.
The strong absorption bands near 1585 and 1515 cm-1 are attributed to the ring C=C
stretching bands. The azomethin stretching bands is observed near 1650 cm-1. Also the
bands near 1707 cm-1 are assigned to the carbonyl stretching band while the bands near
3255 cm-1 are attributed to the hydroxyl group of acid for Schiff bases compounds
A and B.
1
The H NMR spectrum of Schiff base compound A, Figure 1, exhibits singlet
signals at 11.23 and 8.11 ppm, attributed to CH=N and COOH protons respectively16.
The multi signals within the 6.88-7.90 ppm range are assigned to the aromatic protons
of benzene ring. The two signals at 2.33 and 2.05 ppm are assigned to the CH2 and CH3
groups respectively.
1
The H NMR spectrum of Schiff base compound B, Figure 2, is consistent with the
proposed structure. The peak at 11.34 ppm (singlet) corresponds to the carboxylic acid
proton and the one at 8.03 ppm corresponds to the proton of the azomethin group. Moreover,
the triplet at 2.31, doublet at 3.09 and singlet at 2.02 ppm are assigned to the protons of CH,
CH2 and CH3 groups respectively. The peaks around 6.73-7.91 ppm corresponds to the
aromatic protons in the molecule within the NH proton of indole ring.

366 IVAN HAMEED R. TOMI et al.
Figure 1 1H NMR spectrum of compound A.
Figure 2. 1H NMR spectrum of compound B.
Biological activity of compounds A and B on ACP, PAP and NPA enzymes
This work addresses investigation of the effect of compounds A and B on ACP, PAP and
NPA enzymes. The biochemical tests revealed that these compounds caused inhibition and
activation of these enzymes activities. Table 2 and 3 shows the effect of different
concentrations of compound A and B on the activities of ACP, PAP and NPA enzymes in a
human serum. The normal values of ACP, PAP and NPA enzymes activities were 4.80, 0.30
and 4.50 U/L respectively. The relationship between the concentrations of compound A and
the activity of enzymes ACP, PAP and NPA were shown in Figure 3 while Figure 4 shows
the relationship between enzymes activity and compound B concentrations. We suggested
that compounds A and B molecules have (N- and O=) group which interact with active sides
of these enzymes.

Synthesis and Characterization of New Amino Acid-Schiff Bases 369
Table 2. The effect of different concentrations of compound A on the activity of ACP, PAP
and NPA enzymes.
Enzyme
ACP
Conc. M
0
Activity U/L
4.80
Activation %
Inhibition %
-
-
-
-
-
-
-
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
0
1.30
1.70
2.70
2.50
0.30
0.30
0.30
0.30
0.80
4.50
1.00
1.40
2.40
1.70
72.92
64.58
43.75
47.92
-
-
-
-
-
PAP
NPA
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
0
0.00
0.00
0.00
166.67
-
-
-
-
-
-
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
77.78
68.89
46.67
62.22
Table 3. The effect of different concentrations of compound B on the activity of ACP, PAP
and NPA enzymes.
Enzyme
ACP
Conc. M
0
Activity U/L
4.80
Activation %
Inhibition %
-
-
-
-
-
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
0
2.50
2.50
2.80
10.80
0.30
0.30
0.30
0.30
4.90
4.50
2.20
2.20
2.50
47.91
47.91
41.67
-
-
-
-
-
125.00
PAP
NPA
-
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
0
0.00
0.00
0.00
1533.33
-
-
-
-
-
-
5.5×10-2
5.5×10-3
5.5×10-4
5.5×10-5
51.11
51.11
44.44
-
5.90
31.11
6
5
4
3
2
1
0
ACP
PAP
NPA
0
5*10-2
5*10-3
5*10-4
5*10-5
Concentration of compound A [M]
Figure 3. The levels of ACP, PAP and NPA enzymes in the presence of different
concentrations of compound A.

369 IVAN HAMEED R. TOMI et al.
12
10
8
ACP
PAP
NPA
6
4
2
0
0
5*10-2
5*10-3
5*10-4
5*10-5
Concentration of compound B [M]
Figure 4. The levels of ACP, PAP and NPA enzymes in the presence of different
concentrations of compound B.
Tables 2 and 3 show some important results: 1st; compound A inhibit the activity of
ACP and NPA while it exhibits as activator on PAP enzyme activity. 2nd; compound B
shows inhibition and activation of all enzymes activity, these results depending on the
concentration of compound B. 3rd; the activity of the ACP and NPA increasing when the
concentration of the compound A increased. The derivative B showed potent activation of
the PAP at low concentration (5.5×10-5), whereas it showed good activation of ACP and
NPA only at the low concentrations. Thus, it is concluded from the screening results that the
derivatives A and B have good activation and inhibition effects on the activity of these
enzymes.
Conclusion
Two Schiff base compounds A and B derived from glycine and tryptophan were prepared
and structurally characterized using spectroscopic techniques (FT-IR, 1H NMR and
UV-Vis). The synthetic route started from the reaction of these amino acids with 4-methyl
benzaldehyde in alkali absolute methanol. The Schiff base compounds were prepared to
check the effects on the ACP, PAP and NPA enzymes. The biochemical studies revealed
that the derivative A caused activation effects on PAP enzyme activity and inhibition effects
on ACP and NPA enzyme activities while the derivative B caused activation and inhibition
effects on these enzymes depending on its concentration.
Acknowledgment
We thank Mr. Mohanad H. M. Masad (Al al-Bayt University, Jordan) for helpful about
doing the 1H NMR spectra and thermal analysis and Mrs. Zainab K. M. Jawad
(Al-Mustansiriya University; College of Science; Department of Chemistry) about doing the
FT-IR and electronic spectra. Also we are very grateful to department of chemistry, College
of Science, Al-Mustansiriya University for supplying us with some chemicals.
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