Synthesis and in-vitro study of some medicinally important Mannich bases derived from 2-amino-9 [{(1, 3 dihydroxy propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-6-one

Article abstract of DOI:10.4067/S0717-97072012000300017

A series of biologically active Mannich bases with heteroaromatic ring system have been synthesized employing Mannich reaction of 2-amino-9 [{(1,3 dihydroxy propane-2yl) oxy}methyl] 6-9 dihydro-3H-purin-6-one ( potent drug) with biologically active sulphonamides and secondary amines. They were analyzed by elemental analysis and characterized by spectral studies- UV, IR, 1H NMR, Powder X-ray diffraction and Scanning Electron Microscopy. The Mannich bases were screened for their antibacterial activity against various gram + and gram - bacteria. The results had shown that the Mannich bases are quiet active against pathogens under study at varying concentrations. The toxicity of synthesized Mannich bases was ascertained by LD₅₀ test.

Full text of DOI:10.4067/S0717-97072012000300017

J. Chil. Chem. Soc., 57, Nº 3 (2012)
SYNTHESIS AND IN-VITRO STUDY OF SOME MEDICINALLY IMPORTANT
MANNICH BASES DERIVED FROM 2-AMINO-9 [{(1, 3 DIHYDROXY PROPANE-2YL) OXY} METHYL]
6-9 DIHYDRO-3H-PURIN-6-ONE
SHEELA JOSHIA*, PURTI BILGAIYANA AND ANJU PATHAKA
a School of Chemical Sciences, D.A.V.V., Indore 452001,M.P., India
(Received: January 4, 012 - Accepted: May 25, 2012)
ABSTRACT
A series of biologically active Mannich bases with heteroaromatic ring system have been synthesized employing Mannich reaction of 2-amino-9 [{(1,3
dihydroxy propane-2yl) oxy}methyl] 6-9 dihydro-3H-purin-6-one ( potent drug) with biologically active sulphonamides and secondary amines. They were
1
analyzed by elemental analysis and characterized by spectral studies- UV, IR, H NMR, Powder X-ray diffraction and Scanning Electron Microscopy. The
Mannich bases were screened for their antibacterial activity against various gram + and gram - bacteria. The results had shown that the Mannich bases are quiet
active against pathogens under study at varying concentrations. The toxicity of synthesized Mannich bases was ascertained by LD50 test.
Key words: 2-amino-9 [{(1,3 di hydroxy propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-6-one (Ganciclovir), Sulphonamides, Mannich reaction, Mannich
bases, Antibacterial activity , LD50 test.
uncorrected. Thin layer chromatography was used for monitoring the reaction
and to check purity. UV spectra were studied on Schimadzu UV-160A, UV-
visible spectrophotometer; IR spectra (KBr) were recorded as potassium
bromide pellets on Schimadzu 820 IPC FTIR spectrometer and 1HNMR spectra
on Bruker DRX-300 FT NMR Spectrometer and chemical shifts were expressed
as (ppm) values against tetramethylsilane (TMS) as internal reference.
The XRD measurements were carried out on Bruker D8 Advance X-ray
diffractometer using CuKα at a wavelength of 1.54 A°. SEM studies were
performed with a Jeol JSM 5600 instrument having magnification range × 18 to
× 300,000 and at an accelerating voltage of 0.5 to 30kV.The chemical reagents
used in the synthesis were purchased from E. Merck and Aldrich.
1. INTRODUCTION
Heterocyclic compounds are of immense biological and industrial
importance, Majority of pharmaceuticals are heterocyclic1. 2-amino-9 [{(1,3
di hydroxy propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-6-one, an
antiviral agent derived from guanine (heterocyclic compound) are used in the
prevention and treatment of opportunistic cytomegalovirus(CMV) infection
in HIV infected patients and inhibits replication of herpes virus in-vitro. It
helps in keeping CMV infection under control2. The sulphonamide nucleus
has well known pharmacological properties: antibacterial3, anticancer4,
anti-inflammatory5, carbonic inhibitory6, insecticidal7. Even N-morpholino,
piperidino, dimethylamino, diethyl amino Mannich bases show local anesthetic8
and hydrophilic property9.
2.1 Synthesis
2.1.1. Synthesis of Mannich bases from primary amines (3a-3e)
Synthetic pathway for the synthesis of compounds 3a-3e is represented in
Scheme-1. In ethanolic solution of 0.01 mol of Substrate (Comp.-1), 0.01 mol
of sulfonamide and 2.5 mL of formaldehyde solution (37% v/v) were added.
The mixture was kept in an efficient ice cooling for half an hour and then
refluxed on water bath. The refluxed mixture was kept at 0oC for four days
when crystalline product was obtained. The obtained product was recrystallized
with dry distilled ethanol and DMF (1:1). The Mannich bases (3a-3e) were thus
obtained in (≥85%) yield.
These considerations provoked us to synthesize Mannich bases of
2-amino-9 [{(1,3 di hydroxy propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-
6-one using sulphonamides and secondary amines by Mannich reaction, which
may have biological significance. This reaction offers a convenient route to
introduce amino methyl chain, which alters the biological profile and physico-
chemical characteristics of the drug10-12
.
Various drugs obtained from Mannich reaction have proved to be less toxic
and more effective than their parent drug13. The versatile utility of Mannich
bases in polymers14, dispersants15 and pharmaceutical chemistry16 prompted us
to prepare aminomethyl derivatives and evaluate their biological significance.
Here we reports antibacterial activity of Mannich bases of 2-amino-9 [{(1,3
di hydroxyl propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-6-one including
sulphonamide and secondary amines and their comparative study (Table 1).
2.1.2. Synthesis of Mannich bases from secondary amines (3f-3j)
Synthetic pathway for the synthesis of compounds 3f-3j is represented in
Scheme-2. Secondary amine 0.01 mol was added in an ethanolic solution 50
mL of Substrate (Comp. -1) 0.01 mol in a flat bottom flask. Amount of 0.4
mL of formaldehyde solution (37%) was added slowly with constant stirring.
The reaction mixture was stirred at 70-75oC for 3.0 to 8.5 hours, depending
upon the secondary amine. The remaining portion of formaldehyde solution
was added in two installments after 1 and 2 hours, respectively. The reaction
mixture was kept over night in the refrigerator. Next day, the excess of solvent
was distilled off from the reaction mixture under reduced pressure. It was again
kept for crystallization in the refrigerator. The product obtained was purified by
recrystallization from dry distilled ethanol and DMF (1:1). The Mannich bases
(3f-3j) were thus obtained in (≥85%) yield.
In the present work, Mannich bases of 2-amino-9 [{(1, 3 di hydroxy
propane-2yl) oxy} methyl] 6-9 dihydro-3H-purin-6-one were synthesized
by condensation of different primary/secondary amines with formaldehyde.
The substrate first reacts with formaldehyde to form an intermediate, which
then react with sulphonamides/secondary amines in the presence of acid. The
synthesized Mannich bases contains amino methyl group (as justified from the
spectral data), which changes the physiochemical characteristic of the drugs
and makes it less toxic17-18. The synthesized Mannich bases were analyzed for
1
elemental analysis and characterized by spectral studies- UV, IR, H NMR,
Powder X-ray diffraction and Scanning Electron Microscopy.
2.2 Spectral Studies
All the synthesized compounds were evaluated for antibacterial activity
against the pathogenic strains of S.typhi, K.pneumoniae, and P.aeruginosa at
varying concentrations 80, 160, 320 mg/ml. All the Mannich bases had shown
significant activity.
Compound 3a: C20H N O6S, m.p. 160-163oC.Anal. Calcd C,46.40;
H,4.58; N,24.36 Found C2,3469.16;H,4.42; N,24.23. UV (λ max) nm: 208
(C=O), 190 (C=N), 205 (sulfonamide group), 186, 207, 251 (for benzene
chromophore), 254 (sulphonamide moiety). IR (KBr) v max in cm-1: 3442 us
N-H, 3398 uas N-H in SO2NH, 3302 u O-H, 2940 uas CH2, 1688 us C=O, 1345
us S=O, 1130 C-H in plane bending svibration of 1:4 disubstituted benzene.
1H-NMR (DMSO) δ ppm: 5.04 (s, 2H, CH2), 5.5 (s, 2H, CH2 attached to purine
2. EXPERIMENTAL
All the melting points were determined in open capillary tubes and are
e-mail- sheelajoshi2010@gmail.com
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J. Chil. Chem. Soc., 57, Nº 3 (2012)
ring), 6.36 (S, 1H, NH of sulphonamide), 7.93 (s, 1H, CH of purine ring), 7.84
(s, 1H, free OH of Comp.1), 3.72(2CH2 attached with purine ring), 8.65 (N1H of
purine ring), 9.03 (s, 1H of SO2NH), 6.6 – 7.2 (m, ring proton of sulphonamide,
Compound 3c: C20H24N8O S; m.p.180-181°C, Anal. Calcd. C, 46.13; H,
4.65; N, 21.53; Found C, 46.173; H, 4.25; N, 21.33. UV (λ max) nm: 201
(C=O), 192 (C=N), 208 (S=O), 186, 207, 250 for benzene chromophore;
255(sulphonamide moiety). IR (KBr) v max in cm-1
: 3475 us N-H, 3350 uas
N-H in SO2NH, 3318 us O-H, 2915 uas C-H in CH2, 1685 us C=O, 1349 us S=O,
1
1110 C-H in plane bending vibration of 1:4 disubstituted benzene. H NMR
(DMSO) δ ppm: 2.71(s, 3H of CH3)5.04 (s, 2H, CH ), 5.5 (s, 2H, CH attached
to purine ring), 6.3 (s, 1H, NH of sulphonamide), 27.93 (s, 1H, CH 2of purine
ring), 7.84 (s, 1H, free OH of Comp.1), 3.73(2CH2 attached with purine ring),
8.65 (N1H of purine ring), 9.03 (s, 1H of SO2NH), 6.6 – 7.2 (m, ring proton of
sulphonamide,
Compound 3d: C18H N7O7NaS; m.p. 90oC, Anal. Calcd. C, 42.93;
H, 4.41; N, 19.48 Found C,2242.52; H, 4.21; N, 19.22. UV (λ max) nm: 208
(C=O), 190 (C=N), 205 S=O, 186, 207, 251 for benzene chromophore; 254
sulphonamide moiety. IR (KBr) v max in cm-1 : 3482 us N-H, 3351 uas N-H in
SO2NH, 3295 us O-H, 2950 uas C-H in CH2, 1647 us C=O, 1385 us S=O, 1109
disubstituted benzene. 1H NMR (DMSO) δ ppm: 2.16 (s, 3H acetamide CH3)
5.04 (s, 2H, CH2), 5.5 (s,2H,CH2 attached to purine ring), 6.3 (s, 1H, NH of
sulphonamide), 7.9 (s, 1H, CH of purine ring), 6.7 (s, 1H, OH of Comp.1),
3.72(2CH2 attached with purine ring), 8.65 (N1H of purine ring) 9.42 (s, 1H of
SO2NH), 6.6 – 7.07 (m, ring proton of sulphonamide).
Compound 3e: C20H22N O6SAg: m.p. 222oC. Anal. Calcd. C, 38.46;
H, 3.55; N, 20.19 Found C, 398.32; H, 3.51; N, 20.24. UV (λ max) nm: 203
(C=O), 194 (C=N), 208 S=O, 180, 203, 250 for benzene chromophore; 257
sulphonamide moiety. IR (KBr) v max in cm-1 : 3496 us N-H, 3348 u N-H
in SO2NH, 3300 us O-H, 2952 uas C-H in CH2, 1638 us C=O, 1355 usasS=O,
1
1100 C-H in plane bending vibration of 1:4 disubstituted benzene. H NMR
(DMSO) δ ppm: 5.04 (s, 2H, CH2), 5.5 (s, 2H, CH attached to purine ring), 6.1
(s, 1H, NH of sulphonamide), 7.9 (s, 1H, CH of pu2rine ring), 6.72 (s, 1H, OH of
Comp.1), 3.70(2CH2 attached with purine ring), 8.66 (N1H of purine ring), 9.03
(s, 1H of SO2NH) 6.6 – 7.2 (m, ring proton of sulphonamide).
Compound 3f: C14H24N6O6: m.p. 160-162oC. Anal. Calcd. C, 45.14;
H, 6.49; N, 22.56 Found C, 45.13; H, 6.51; N, 22.50. UV (λ max) nm: 208
(C=O), 191 (C=N), 185 205, 250 for benzene chromophore. IR (KBr) v max in
cm-1 : 3482 us N-H, 3352 us O-H, 2944 uas C-H in CH , 1680 u C=O. 1H NMR
(DMSO) δ ppm : 4.51 (s,2H,CH2), 5.60 (s,2H,CH2 att2ached to spurine ring), 7.9
(s, 1H, CH of purine ring), 4.92 (s, 1H, OH of Comp.1), 3.72(2CH2 attached
with purine ring), 8.65 (N1H of purine ring) .
Scheme 1. Synthesis of Mannich bases from primary amines.
Compound 3g : C12H20N6O4: m.p. 225-227oC, Anal. Calcd. C, 46.13;
H, 6.46; N, 26.90 Found C, 46.4; H, 6.51; N, 26.82. UV (λ max) nm: 210
(C=O), 195 (C=N), 185, 205, 255 for benzene chromophore. IR (KBr) v max
in cm-1: 3412 us N-H, 3310 us O-H, 2909 uas C-H in CH2, 1655 us C=O. 1H NMR
(DMSO) δ ppm: 2.23(s, 3H of methyl group), 4.48 (s, 2H, CH2), 5.5 (s, 2H,
CH2 attached to purine ring), 7.9 (s, 1H, CH of purine ring), 6.12 (s, 1H, OH
of Comp.1) 3.72(2CH2 attached with purine ring), 8.65 (N1H of purine ring) .
Compound 3h : C H22N6O5; m.p. 215-218oC., Anal. Calcd. C, 47.43; H,
6.26; N, 23.71 Found C1,447.32; H, 6.30; N, 23.52. UV (λ max) nm: 204 (C=O),
190 (C=N), 184, 209, 254 for benzene chromophore. IR (KBr) v max in cm-1:
3477 us N-H, 3361 us O-H, 2947 uas C-H in CH2, 1630 us C=O, 1244 us C-O.
1H NMR (DMSO) δ ppm: 4.4 (s, 2H, CH2), 5.5 (s,2H,CH2 attached to purine
ring), 7.93 (s, 1H, NH of purine ring), 6.21 (s, 1H, OH of Comp.1) 3.72(2CH2
attached with purine ring), 8.65 (N1H of purine ring), .
Compound 3i : C H24N6O4; m.p. 235-236oC, Anal. Calcd. C, 60.52; H,
5.55; N, 19.25 Found C2,260.61; H, 5.32; N, 19.10. UV (λ max) nm: 209 (C=O),
190 (C=N), 184, 206, 260 for benzene chromophore. IR (KBr) v max in cm-
1
1: 3406 us N-H, 3318 us O-H, 2932 uas C-H in CH2, 1643 u C=O. H NMR
(DMSO) δ ppm: 4.5 (s, 2H, CH2), 5.5 (s, 2H, CH2 attached tospurine ring), 7.9
(s, 1H, CH of purine ring), 6.17 (s, 1H, OH of Comp.1), 3.72(2CH2 attached
with purine ring), 8.60 (N1H of purine ring).
Compound 3j : C14H23N7O4: m.p. 220oC. Anal. Calcd C, 47.57; H, 6.56;
N, 27.74 Found C, 47.80; H, 6.32; N, 27.62. UV (λ max) nm: 205 (C=O), 190
(C=N), 184, 206, 260 for benzene chromophore. IR (KBr) v max in cm-1: 3458
u N-H, 3342 us O-H, 2937 u C-H in CH , 1639 u C=O. 1H NMR (DMSO) δ
pspm: 4.5 (s, 2H, CH ), 5.5 (sa,s2H, CH2 att2ached to spurine ring), 7.9 (s, 1H, CH
of purine ring), 5.5 2(s, 1H, OH of Comp.1) 3.72(2CH2 attached with purine
ring), 8.67 (N1H of purine ring),.
Scheme 2. Synthesis of Mannich bases from secondary amines.
Compound 3b: C20H22N9O8S, m.p. 105-107oC. Anal. Calcd. C, 45.74;
H, 4.71; N, 21.82; Found C, 45.61; H, 4.46; N, 21.64. UV (λ max) nm: 210
(C=O), 197 (C=N), 208 S=O, 182, 205, 250 for benzene chromophore; 258
sulphonamide moiety. IR (KBr) v max in cm-1 : 3440 us N-H, 3380 u N-H
in SO2NH, 3302 us O-H, 2910 uas C-H in CH2, 1653 us C=O, 1380 usasS=O,
Powder X-ray diffraction studies
1
Powder X-ray diffraction patterns of three of the synthesized compounds
namely ganciclovir methyl silver sulphadiazine (3e), ganciclovir methyl
diphenylamine (3i) and ganciclovir methyl Piperazine (3j) (Fig 1,2 and 3
respectively) have been reported and important structural information have
been shown in table 1,2,and 3 respectively.
1135 C-H in plane bending vibration of 1:4 disubstituted benzene; H NMR
(DMSO) δ ppm: 3.43 (s, 3H of OCH3) 5.04 (s,2H,CH2), 5.5 (s,2H,CH attached
to purine ring), 6.4 (s, 1H, NH of sulphonamide), 7.9 (s, 1H, CH 2of purine
ring), 7.4 (s, 1H, free OH of Comp.1), 3.74(2CH2 attached with purine ring),
8.66 (N1H of purine ring) 9.2 (s, 1H of SO2NH), 6.6 – 7.07 (m, ring proton of
sulphonamide).
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J. Chil. Chem. Soc., 57, Nº 3 (2012)
Figure 1. Powder X-ray diffraction pattern of Ganciclovir methyl Silver
Sulphadiazine (3e).
Figure 3. Powder X-ray diffraction pattern of Ganciclovir methyl
Piperazine (3j).
Table1 . The experimental data and the calculated results for powder
X-ray pattern of the ganciclovir methyl Silver Suldhadizine(3e).
Average particle size of the synthesized compound was determined with
the help of the Scherrer formula, in which particle size D is defined as 0.9λ/
B cos θ,
Where 0.9 = constant, λ = wavelength, B = angular width
And θ = diffraction angle. Average particle size of the compound
determined were 94.18, 32.03 and 64.13 nm respectively. Diffraction data of
the compounds are listed in table 1,2 and 3. All of our synthesized compounds
had a
d spacing(A°)
Observed
d spacing(A°)
Calculated
Relative
intensity (%)
2θ
h k l
19.79
20.58
22.37
24.19
25.53
26.59
27.79
29.17
30.81
31.98
33.09
34.50
35.94
37.08
38.43
39.45
40.89
43.17
45.99
47.78
48.89
49.21
4.48
4.31
3.96
3.67
3.48
3.34
3.20
3.05
2.89
2.79
2.70
2.59
2.49
2.42
2.33
2.28
2.20
2.09
1.97
1.90
1.86
1.84
4.46
4.14
4.00
3.67
3.48
3.04
3.32
3.31
2.73
2.85
2.46
2.59
2.40
2.42
2.33
2.26
2.36
2.46
1.98
2.20
2.13
1.81
98.96
73.17
43.61
84.83
37.33
50.69
100
210
023
220
004
141
043
133
114
152
134
134
060
045
340
400
260
106
161
360
421
171
520
19.97
22.32
46.99
55.81
25.63
27.90
32.71
42.30
15.31
29.36
24.98
31.87
19.51
15.74
17.32
Figure 2. Powder X- Ray diffraction pattern of Ganciclovir methyl
diphenylamine (3i).
Orthorhombic crystal system and XRD patterns showed that all are
polycrystalline in nature. The largest relative deviation between the calculated
and experimental d value was nearly equal to one, which indicates that all the
synthesized compounds are multiphase compounds. Interplaner d spacing and
unit cell volume of the synthesized compound were calculated by the formulae:
Lattice parameters and angle calculated are: a = 9.32 A° or 0.93nm, b
= 15.54 A° or 1.55nm, C = 14.68 A°or 1.46nm, β = 94.18°. Unit cell
volume of the complex: 2,126.14×10-8 cm
1/ d2 = h2/a2 + k2 /b2 + l2/ c2
V = abc
Peaks having important characteristics information have been identified
with the help of standard diffraction card JCPDS 31-1859, 38-1709, 49-2499
and 35-1687 and indicate formation of nanosized, polycrystalline, two phase
and low symmetry compounds.
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J. Chil. Chem. Soc., 57, Nº 3 (2012)
Scanning Electron Microscopy (SEM) Studies
Table2. The experimental data and the calculated results for powder X-ray
pattern of the ganciclovir methyl biphenyl amine(3i).
Scanning Electron Microscopy Studies of two of the synthesized compound
namely ganciclovir methyl silver sulphadiazine (3e), and ganciclovir methyl
Piperazine (3j) have been carried out at a magnification of ×1,000 - 10 µm and
× 600 - 2µm. SEM uses a focused beam of high energy electrons to generate
a variety of signals from the surface of a signals reveal information about the
sample, including external morphology, topography, chemical composition
crystalline structure, and orientation of materials making up the sample.
d spacing
(A°)
Observed
d spacing
(A°)
Calculated
Relative
intensity
(%)
2θ
h k l
10.97
14.87
20.76
21.99
23.75
24.74
27.97
29.05
30.46
32.30
36.46
37.61
38.40
40.04
44.00
45.02
46.81
47.04
48.54
49.15
8.05
5.94
4.27
4.03
3.74
3.59
3.18
3.06
2.14
2.76
2.46
2.38
2.34
2.24
2.05
2.01
1.93
1.92
1.87
1.85
8.00
5.94
4.24
4.00
4.20
3.56
3.18
3.34
3.01
3.28
2.61
2.96
2.34
2.25
2.40
1.98
1.93
2.18
2.10
1.81
27.38
10.07
22.82
31.25
100
110
120
102
220
201
140
003
202
103
212
302
301
400
260
161
360
080
421
171
520
15.36
10.12
10.54
8.14
17.48
7.52
7.94
7.63
7.28
7.03
6.48
7.01
6.98
Figure 4
7.49
6.18
Lattice parameters and angle calculated are: a = 9.36 A° or 0.93nm, b =
15.44 A° or 1.54nm, C = 9.54A°or 0.954nm, β = 32.03°.Unit cell volume
of the complex: 1,378.70×10-8 cm.
Table3. The experimental data and the calculated results for powder
X-ray pattern of the ganciclovir methyl Piperazine(3j).
d
d
Relative
intensity
(%)
2θ
spacing(A°)
Observed
spacing(A°)
Calculated
h k l
19.85
22.25
23.78
25.71
27.97
28.67
30.08
31.98
34.76
39.16
40.16
41.68
43.06
44.26
46.81
47.89
49.39
4.53
4.06
3.81
3.54
3.28
3.20
3.07
2.90
2.70
2.43
2.38
2.31
2.25
2.20
2.11
2.07
2.02
4.53
4.12
3.81
3.51
3.38
3.27
3.51
2.80
2.72
2.43
2.95
2.83
2.21
2.52
2.14
2.41
1.94
10.43
46.49
100
200
113
040
140
042
133
140
320
025
006
301
151
260
144
206
161
360
21.29
6.57
55.90
4.90
7.92
14.79
4.59
4.99
6.86
4.76
4.55
4.96
6.18
4.30
Figure 5
We recorded different magnifications, as described above. Compound
ganciclover methyl silver sulphadiazine (3e) (Fig 4 and 5) has a different
topography and morphology at the two different magnifications. In the images,
the particles exhibit different sizes and shapes, and are present in the form of
closed polygonal structure hand, the compound ganciclover methyl Piperazine
(3j) (Fig 6 and 7) shows at different magnifications a finer morphology
as compared to the other compound, appears in form of simple polygonal
structures.
Lattice parameters and angle calculated are: a = 9.06 A° or 0.90 nm,
b = 15.24 A° or 1.52nm, C = 14.58 A°or 1.45nm, β = 64.13°.Unit cell
volume of the complex: 2,013.12×10-8 cm.
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J. Chil. Chem. Soc., 57, Nº 3 (2012)
incorporated between active hydrogen substrate and the amine component as a
result of Mannich reaction at 2940-2950 cm-1 and 1442-1450 cm-1. This shows
the presence of amino methyl linkage in the synthesized Mannich bases. The
1H NMR also confirms aminomethyl linkage (-CH2) between amine and active
hydrogen (5.04-5.20 ppm). Some of the synthesized compounds are of nano
size. The use of nano particle in medicine offers some exciting possibilities.
Some techniques are only imagined, while others are at various stage of
testing, or actually being used today.The Mannich bases were screened for
their biological significance. They were evaluated for antibacterial activity
against pathogenic strains of S.typhi, P.aeruginosa and K.pneumoniae. at
varying concentrations–80mg/ml, 160mg/ml and 320 mg/ml. All the reported
compounds exhibit remarkable in vitro activity against these pathogens. Their
activity was also compared with their parent sulphonamides.
Table 4 Antibacterial screening of synthesized Mannich Bases and
sulphonamides against S.typhi, K.pneumoniae and P.aeruginosa (Zone of
inhibition in mm).
S.typhi
K.pneumoniae
P.aeruginosa
(Concn. in µg/mL)
(Concn. in µg/mL)
(Concn. in µg/mL)
Comp.
No
Figure 6
80 160 320 Av
80 160 320 Av
80 160 320 Av
3a
3b
3c
3d
3e
3f
7.3 9.3 11.0 9.2
7
7.3 10.3 8.2
-
-
7.3 8.3 5.2
7.0 2.3
7
7.6 9.3 7.9
7.3 2.4
7.3 9.3 11.6 9.4
8.6 2.8
7.0 8.3 10.6 8.6
9.6 13.6 18.3 13.8
10.6 17.6 21.6 16.6
-
-
-
-
-
9.6 12.6 20.3 14.2
7.0 8.6 10.3 8.6
7.3 8.3 12.3 9.3
-
-
-14.0
-
18.3 20.3 17.5
7.6 10.6 16.3 11.5
-
7.3 9.6 5.6
3g
3h
3i
-
-
-
-
9.3 3.1
-
-
7.0 2.3
-
-
-
8.6 2.8
-
-
7.3 8.0 11.6 8.9
8.3 8.6 10.3 9.0
-
-
-
7.3 8.6 10.0 8.6
7.3 9.0 11.6 9.3
3j
1
-
-
-
-
-
-
-
-
7.0
-
-
7.3
-
8.6 2.8
8.3 5.1
7.3 2.4
-
-
-
-
-
-
-
-
9.0 3.0
8.0 2.6
10.6 3.5
-
-
-
2a
2b
2c
2d
2e
13.6 21.0 24.3 9.5
10.3 14.3 17.6 14.1
10.3 14.3 11.6 12.1
12.3 17 21.3 16.8
9.3 11.6 16.6 2.3
7.3 13.3 6.8
8.3 9.3 8.2
-
-
7
9.3 5.5
9.6 13.3 19.6 14.1
-
-
-
-
-
-
-
9.6 3.2
-
9.6 13.3 7.6
Table-4 reflects that most of the compounds had shown remarkable
activity only at 320 mg/ml.
Antibacterial screening of Mannich bases against S. typhi, showed
interesting results (Table 4). That reflects, Mannich bases 3a and 3d were at
par in their antibacterial activity followed by 3f and 3i were superior to other
Mannich bases in case of S. typhi. All the Mannich bases were found to be
significantly superior to their corresponding sulphonamide except 3c.
Mannich base 3e followed by 3c was found to superior in inhibitory effect
against K. pneumoniae over other compounds. The antibacterial activity was
compared with parent sulphonamides. It was found that sulphonamides were
equally potential against K. pneumoniae as the synthesized Mannich bases.
Table 1 reflects that except 3h all the synthesized Mannich bases had proven
to be potent against P.aeruginosa, 3c are significantly superior to others in
inhibiting the growth of this pathogen. Mannich bases 3e and 3i are at par their
antibacterial activity followed by 3d in inhibiting the growth of this pathogen.
Figure 7
SEM studies show microstructure of the compounds, which mainly
include surface morphology.
2.3. Antimicrobial Activity
The study was performed by the cup plate method19 on pathogenic strains
of S.typhi, P.aeruginosa and K.pneumoniae. The media used for antibacterial
screening were from hi-media. The media were prepared in triple distilled
water and autoclaved at 15 lb pressure. The culture of bacterium was mixed
with autoclaved media, poured in plates, and bored. The solution of Mannich
bases were poured in these cups in triplicate and incubated at 37οc for 24 hours.
The Mannich bases (3a-3j) were studied for their antibacterial property at
concentration of 80, 160, 320 mg/mL.
2.4 LD50 Test
4. CONCLUSION
The toxicity of synthesized Mannich bases was ascertained by LD test.
The test performed on white mice weighing 25g. Doses were given 5o0 rally
as well as intraperitoneally and mice were kept under observation for 72 hr
for each trial. The Mannich bases showed no adverse toxic effect even of an
oral dose of 1400mg/kg of the body weight of mice. However when dose was
administered intraperitoneally they proved be lethal at the does level of 800mg/
kg of the body weight of mice.
Conclusion suggest that the newly synthesized Mannich bases of 2-amino-9
[{(1,3 di hydroxy propane-2yl) oxy} methyl] 6-9 dihydro-3H-purine-6-one
possess a very noticeable and prolonged antibacterial activity. These derived
Mannich bases are less toxic in comparison of their parent sulphonamides.
This work shows that Mannich bases are a potential source of compounds for
inhibition of bacteria and could be used as efficient drugs with minimum side
effects.
3. RESULTS AND DISCUSSION
ACKNOWLEDGEMENT
The Mannich bases synthesized by Mannich reaction were obtained in
good yield (≥85%). They were analyzed for elemental analysis and results
were found to be in full agreement with the calculated values. The anticipated
structure was in agreement with the spectral data– UV, IR and 1HNMR.
The spectral studies have shown characteristic band due to methylene group
Our sincere thanks are due to CSMCRI, Bhavnagar for elemental analysis,
SAIF Chandigarh and UGC-DAE CSR Indore for spectral studies. We also
extend our sincere thanks to Dr. Tushar Banerjee, School of Life Sciences,
DAVV, Indore for providing facilities to conduct antibacterial studies.
1281

J. Chil. Chem. Soc., 57, Nº 3 (2012)
Press, BOCA Raton, 1994, Ch.1, pp 07.
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