SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL ACTIVITY OF VARIOUS SUBSTITUTED BENZOTHIAZOLE DERIVATIVES
HEMLATA KAUR, SUNIL KUMAR, INDU SINGH, K.K. SAXENA, ASHOK KUMAR*
Medicinal Chemistry Division, Department of Pharmacology, L.L.R.M. Medical College, Meerut 250004, U.P. India
A series of 2-(benzo[d]thiazol-2-ylthio)-N-(2-oxoindolin-3-ylidene)acetohydrazide (3a- 3g), 2-(benzo [d]thiazol-2-ylthio)-N-(2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4a-4g) and 2'-((benzo[d]thiazol-2-ylthio)methyl)spiro[indoline-3,5'- thiazolo[4,3-b][1,3,4]oxadiazol]-2-ones (5a-5g) have been synthesized and screened for their anti-inflammatory, analgesic and antibacterial activities. The most potent anti- inflammatory and antibacterial compound of this series was compound 5d and most potent analgesic compound was compound 5e. Structures of all the compounds were established by elemental and spectral (IR and 1H NMR) analysis.
(Received February 11, 2010; February 24, 2010)
Keywords: Benzothiazoles, Indoles, Thiazolidinones, Oxadiazoles, Anti-inflammatory Activity,Analgesic activity, Antibacterial activity, Acute toxicity
1. Introduction
Bacterial infections often produce inflammation and pain. In normal practice, two groups of agents (chemotherapeutic, analgesic and anti-inflammatory) are prescribed simultaneously. The compounds prossessing all three activities are not common benzothiazole derivatives have received the attention of medicinal chemists due to their wide range of biological activities which include anti-inflammatory [1], analgesic [2], antibacterial [3] and antiviral [4] activities. Literature survey reveals that indole and thiazolidinone derivatives are important for anti-inflammatory [5, 6], analgesic [7,8], antibacterial [9,10], and antipsychotic [11,12] activities. Also several oxadiazole derivatives have been found to be of interest with potential activities including anti- inflammatory [13], analgesic [14] and antibacterial [15], insecticidal [15] activities. In the present study it was envisaged that a drug molecule possessing the above mentioned pharmacophore could be of advantage since it might possess analgesic, anti-inflammatory and antibacterial activities.
2. Results and discussion
Results Chemistry
Synthetic route of benzothiazole derivatives is outlined in scheme 1. Accordingly reaction of 2-mercaptobenzothiazole with ethyl chloro acetate in dry acetone in presence of K2CO3 afforded the Ethyl 2-(benzothiazolylthio) acetate (1). Compounds 1 was treated with hydrazine hydrate in ethanol to afford compound 2 which was reacted with various substituted indole-2,3- diones in refluxing methanol to afford compounds 3a-3g which were cyclized with mercaptoacetic acid into corresponding thiazolidinone derivatives i. e. compounds 4a-4g. Compounds 4a-4f on reaction with sulfuric acid in methanol yielded compounds 5a-5g.
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*Corresponding author: [email protected]
Pharmacology
Anti-inflammatory activity against carrageenan induced oedema
All the newly synthesized compounds and reference drug phenylbutazone and aspirin have been examined for their anti-inflammatory activity. The pharmacological results of synthesized compounds have been reported in Table 1. All the compounds have shown anti-inflammatory activity ranging from 10.8-44.8% at the dose of 50 mg/kg p.o. It is clear that when the compounds as substituted with 5-chloro indole moiety (i.e. compound 3d 17.8%) showed better anti- inflammatory activity than compounds substituted with 7-chloroindole moiety (i.e. compound 3e).
The compound 3f and 3g substituted by 5-bromo and 7-bromoindole moieties respectively were less active than compounds 3d but more active than compounds 3a-3c.
Table 1. Physical and analytical data of compounds 1, 2, 3a-3g, 4a-4g and 5a-5g.
Elemental analysis Calc. (Found) % Com.
No.
R MP Molecular
Formula C H N
1 - 58 C11H11NO2S2 52.18 (52.17) 4.22 (4.20) 5.40 (5.42) 2 - 193 C9H9N3OS2 45.22 (45.23) 3.10 (3.09) 17.60 (17.65) 3a. 5-
OCH3
210 C18H14N4O3S2 54.26 (54.27) 3.54 (3.53) 14.06 (14.05) 3b. 5-CH3 220 C18H14N4O2S2 56.53 (56.50) 3.69 (3.67) 14.65 (14.69) 3c. 7-CH3 214 C18H14N4O2S2 56.53 (56.52) 3.69 (3.65) 14.65 (14.66) 3d. 5-Cl 230 C17H11ClN4O4S2 50.68 (50.67) 2.75 (2.74) 13.91 (13.92) 3e. 7-Cl 228 C17H11ClN4O4S2 50.68 (50.69) 2.75 (2.75) 13.91 (13.92) 3f. 5-Br 222 C17H11BrN4O2S2 45.64 (45.63) 2.48 (2.49) 12.52 (12.55) 3g. 7-Br 225 C17H11BrN4O2S2 45.64 (45.66) 2.48 (2.48) 12.52 (12.53) 4a. 5-
OCH3
251 C20H16N4O4S3 50.83 (50.86) 3.41 (3.40) 11.86 (11.83) 4b. 5-CH3 246 C20H16N4O3S3 52.61 (52.65) 3.53 (3.55) 12.27 (12.30) 4c. 7-CH3 252 C20H16N4O3S3 52.61 (52.64) 3.53 (3.55) 12.27 (12.26) 4d. 5-Cl 269 C19H13ClN4O3S3 47.84 (47.80) 2.75 (2.79) 11.75 (11.76) 4e. 7-Cl 263 C19H13ClN4O3S3 47.84 (47.81) 2.75 (2.79) 11.75 (11.75) 4f. 5-Br 258 C19H13BrN4O3S3 43.76 (43.77) 2.51 (2.56) 10.74 (10.70) 4g. 7-Br 260 C19H13BrN4O3S3 43.76 (43.75) 2.51 (2.54) 10.74 (10.72) 5a. 5-
OCH3
280 C20H14N4O3S3 52.85 (52.87) 3.10 (3.12) 12.33 (12.37) 5b. 5-CH3 286 C20H14N4O2S3 54.78 (54.72) 3.22 (3.27) 12.78 (12.78) 5c. 7-CH3 282 C20H14N4O2S3 54.78 (54.74) 3.22 (3.26) 12.78 (12.73) 5d. 5-Cl 298 C19H11ClN4O2S3 49.72 (49.70) 2.42 (2.43) 12.21 (12.24) 5e. 7-Cl 290 C19H11ClN4O2S3 49.72 (49.73) 2.42 (2.47) 12.21 (12.23) 5f. 5-Br 295 C19H11BrN4O2S3 45.33 (45.30) 2.20 (2.23) 11.13 (11.15)
5g. 7-Br 290 C19H11BrN4O2S3 45.33 (45.30) 2.20 (2.22) 11.13 (11.16)
It is interestingly enough, the anti-inflammatory activity of 2-(benzo[d]thiazol-2-ylthio)- N-(2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’-yl)acetamides (4a-4g) were more (15.9-27.2%) than that of their parent compounds i.e. compounds 3a-3g. Among the compounds 4a-4g, compound 4d (having 5-chloroindole moiety) exhibited 27.2% protection against carrageenan induced oedema. Cyclization of compounds 4a-4g into their corresponding oxadiazole ring (i.e.
compounds 5a-5g), very clearly showed an increase in anti-inflammatory activity (28.6-44.8%) at dose of 50 mg/kg p.o. Compound 5d and 5e were also tested at three graded doses i.e. 25, 50 and 100 mg/kg p.o. The compound 5d showed 31.4% anti-inflammatory activity at a dose of 25 mg/kg p.o. and 44.8 and 72.2% anti-inflammatory activity at the dose of 50 mg/kg and 100mg/kg p.o respectively. Moreover, compound 5e showed 30.6, 36.4 and 68.8% anti-inflammatory activities at the dose of 25, 50 and 100 mg/kg p.o. respectively.
Table 2. Anti-inflammatory and analgesic activity of compounds 3a-3g, 4a-4g and 5a-5g.
HN R
O S N
(3a-3g) HN N S O
HN R
N S O S
N
HN
S O O
(4a-4g)
HN R
N S S
N
N
(5a-5g) S O
O
Comp.
No.
Dose (mg/kg p.o.)
Antiinflammatory activity % oedema inhibition
relative to control
Analgesic activity % decrease of writhes
in 60 min after treatment relative to
control
∑ π (P value)
ALD50 mg/kg i.p.
3a. 50 10.8* 12.6* -12 >1000
3b. 50 13.5* 8.8* 1.29 >1000
3c. 50 11.5** 10.8** 1.25 >1000
3d. 50 17.8** 14.7** 2.00 >1000
3e. 50 15.6** 12.4** -11 >1000
3f. 50 14.4** 12.2** 2.00 >1000
3g. 50 12.8** 11.8** 1.29 >1000
4a. 50 15.9** 13.2*** 1.27 >1000
4b. 50 18.4** 14.5** 2.15 >1000
4c. 50 24.6** 14.8** 1.29 >1000
4d. 50 27.2*** 16.6** 3.53 >1000
4e. 50 20.7** 18.6** 3.38 >1000
4f. 50 26.1*** 18.6** 3.53 >1000
4g. 50 18.6** 16.3** 2.67 >1000
5a. 50 31.2*** 25.2*** 1.29 >1000
5b. 50 31.4*** 25.9*** 1.27 >1000
5c. 50 28.6*** 29.5*** 2.15 >1000
5d. 25 50
100
31.4***
44.8***
72.2***
30.1 ***
32.2***
55.5***
3.38 >1400
5e. 25 50
100
30.6***
36.4***
68.8***
33.6***
43.4***
69.2***
3.53 >1400
5f. 50 32.2*** 27.6*** 3.53 >1000
5g. 50 30.8*** 27.3*** 2.67 >1000
Phenyl Butazon e
25 50 100
31.4***
40.6***
63.4***
31.0***
32.5***
42.6***
Aspirin 25 30.25*** 30.2***
50 100
38.4***
60.8***
45.5***
59.3***
*P < 0.05, **P < 0.01, ***P < 0.001 Analgesic activity
All the newly synthesized compounds 3a-3g, 4a-4g and 5a-5g were screened for their analgesic activity at a dose of 50 mg/kg p.o. From the results it is clear that the compounds (i.e.
compound 5d) which exhibited better inflammatory activity and was associated with less analgesic activity (32.2 and 55.5%) at the dose of 50 and 100 mg/kg respectively. Furthermore, compound 5e (having 7-chloro indole moiety) showed 43.4 and 69.2% analgesic activity at the dose of 50 and 100 mg/kg p.o.
Table 3. Antibacterial activity of compounds 3a-3g, 4a-4g and 5a-5g.
Zone of inhibition (diameter in mm) Com.
No.
R
K. Pneumoniae S. aureus E. coli
Control - Nil Nil Nil
Ciprofloxacin - 26 23 25
3a. 5-OCH3 - - 8
3b. 5-CH3 12 - 12
3c. 7-CH3 10 -
3d. 5-Cl 11 10 12
3e. 7-Cl 13 12 -
3f. 5-Br 8 - 10
3g. 7-Br 10 17 20
4a. 5-OCH3 - 18 -
4b. 5-CH3 15 12 -
4c. 7-CH3 - 18 20
4d. 5-Cl 18 17 -
4e. 7-Cl 17 - 22
4f. 5-Br 20 14 24
4g. 7-Br - - 25
5a. 5-OCH3 18 10 15
5b. 5-CH3 - 16 18
5c. 7-CH3 16 - 19
5d. 5-Cl 28 24 25
5e. 7-Cl 22 22 20
5f. 5-Br 21 19 16
5g. 7-Br 19 20 16
Antibacterial activity
All the newly synthesized compounds were also tested for their antibacterial activity against K. pneumoniae, S. aureus and E. coli. From the table it is clear that compound 5d namely2'-((benzo[d]thiazol-2-ylthio)methyl)-5-chlorospiro[indolin-3,5'-thiazolo[4,3-b]
[1,3,4]oxadiazol]-2-one exhibited maximum antibacterial activity (i.e. 28, 24 and 25mm zone of inhibition) against all the bacterial strains in comparison to the other compounds. Moreover, compound 5e having 7-chloroindole moiety showed good antibacterial activity against K.
pneumoniae, S. aureus and E. coli (i.e. 22, 22 and 20mm zone of inhibition respectively).
Compounds 3a and 4g were devoid of antibacterial activity against K. pneumoniae and S. aureus.
S N
SH
Cl O
O CH3
S N
S O
CH3 O Anh. K2CO3, dry Acetone
MWI NH2.NH2, ethanol
S N
S
HN NH2 O (1)
(2)
NH O
O R
HN R
O S N
(3a-3g)
HN R
N S O S
N
HN
S O O
(4a-4g)
HN N S O
HN R
N S S
N
N
S OH
Conc. H2SO4
HN R
N S S
N
N
(5a-5g)
O O
S
O HO
Scheme 1:Synthetic route of Benzothiazole derivatives
HSCH2COOH/DMF/ZnCl2
3. Conclusions
- Benzothiazole derivatives with chloroindole moieties give the interesting activity (as the electro negativity of chloro group increase the activity) increases.
- The bromo subtituents also showed good activity.
- 5-chloroindolylbenzothiazole derivative (i.e. compound 5d) exhibited most potent anti-
inflammatory and antibacterial activities, while 7-chloroindolylbenzothiazole derivative (i.e.
compound 5e) exhibited most potent analgesic activity.
- The oxadiazole ring is essential for high anti-inflammatory, analgesic and antibacterial activities
4. Experimental
All reagents and solvents used were of HIMEDIA, CDH and Merck. The melting points were determined in open capillaries tubes on a Jyoti Laboratories melting point apparatus and were uncorrected. The purity of the compounds was confirmed by TLC using silica gel G as stationary phase, using two solvent; by TLC using silica gel G as stationary phase, using two solvent systems; Benzene:Ethanol (9:!) and Toluene:Ethyl formate: Formic acid (5: 4:1) and visualized in iodine. The IR spectra were recorded in potassium bromide on a Perkin Elmer IR spectrometer.
1H-NMR spectra were recorded in CDCl3 and DMSOd6 at 300 MHz on Bruker spectrometer and all chemical shifts were given in ppm relative to tetramethylsilane. The elemental analyses (C, H, N) were performed using Perkin-Elmer model 240c analyzer. The animal research study was approved by the animal ethical committee (CPCSEA).
Preparation of Ethyl 2-(benzothiazolylthio)acetate (1)
Dissolve the 2-Mercaptobenzothiazole (2.0 mol) in methanol and ethyl chloro acetate (2.0 mol) was added dropwise in presence of K2CO3 (8 g) in the mixture with stirring. The resulted mixture was refluxed for 10 hours and the reaction mixture poured into ice cold water and neutralized with dil HCl. The semisolid thus obtained was washed several times with water and left in water for 72 hours. The crystals formed were filtered, washed thoroughly with water and dried. The completion of the reaction was mentioned on T.L.C. by using silica Gel G coated plates by using ethyl acetate and petroleum ether (1:1) as the eluent and observed in UV light and Ethyl- 2-(1H-indol-3’-yl) acetate was obtained.
Preparation of 2-(benzo[d]thiazol-2-ylthio)acetohydrazide (2)
A mixture of 253.3 g 1 (1 mol,) and hydrazine hydrate (0.4 mol) and ethanol (40 ml) was taken RBF placed in microwave oven and irradiated for 4 min. After completion of reaction (monitored by TLC), mixture was cooled and the resulting solid was filtered, dried and recrystallized from ethanol to yield compound 2.
Preparation of 2-(benzo[d]thiazol-2-ylthio)-N-(2-oxoindolin-3-ylidene)acetohydrazide (3a-3g)
A mixture of 191.4 g of 2 (0.8 mol) and various substituted indole-2,3-dione (0.8 mol) in methanol (60 ml) in the presence of a catalytic amount of gl. acetic acid was heated under reflux for 30 min. The solid that separated on cooling was filtered, washed with cold methanol and recrystallized from methanol to give compounds 3a-3g.
Preparation of 2-(benzo[d]thiazol-2-ylthio)-N-(2,4’-dioxospiro[indolin-3,2’- thiazolidin)-3’-yl) acetamides (4a-4g)
A mixture of 119.5 g of 3a-3g (0.3 mol) and mercaptoacetic acid (0.3 mole) in DMF (100 ml) containing a pinch of anhyd. ZnCl2 was heated under reflux for 6-8 h. The reaction mixture was cooled and poured onto crushed ice. The solid thus obtained was filtered, washed with water and recrystallized from DMF to afford 4a-4g.
Preparation of 2'-((benzo[d]thiazol-2-ylthio)methyl)spiro[indolin-3,5'-thiazolo[4,3-
b][1,3,4] oxadiazo l]-2-ones (5a-5g)
Compound 70.8 g 4a-4f (0.15 mol) was added slowly to conc. H2SO4 (10 ml) in the cold.
The reaction mixture was kept for 6 h. at room temperature, poured onto crushed ice and neutralized with ammonia solution. The precipitate thus obtained was filtered, washed with water and recrystallized from DMF to furnish compounds 5a-5g.
IR and 1H-NMR data of compounds 1, 2, 3a-3g, 4a-4g and 5a-5g:
Ethyl 2-(benzothiazolylthio)acetate (1)
Yield: 86%; IR (KBr): 3020 1720, 1612, 696 cm-1. 1H-NMR: δ (ppm): 1.23 (3H, t), 4.13 (2H, q), 4.46 (2H, s), 6.79-7.87 (4H, m).
2-(benzo[d]thiazol-2-ylthio)acetohydrazide (2)
% Yield: 84, IR (KBr): 3020, 1720, 1612, 694 cm-1. 1H-NMR: δ (ppm): 4.42 (2H, s), 4.80 (2H, s), 6.70-7.80 (4H, m), 7.89 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-methoxy-2-oxoindolin-3-ylidene)acetohydrazide (3a)
% Yield: 76; IR (KBr): 3207, 1732, 1665, 1608, 698 cm-1. 1H-NMR: δ (ppm): 3.50 (3H, s), 4.83 (2H, s), 6.73-7.81 (7H, m), 8.13 (1H, s), 8.80 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-methyl-2-oxoindolin-3-ylidene)acetohydrazide (3b)
% Yield: 70; IR (KBr): 3220, 1730, 1666, 1605, 690 cm-1. 1H-NMR: δ (ppm): 1.10 (s, 3H, CH3), 4.79 (2H, s), 6.78-7.88 (7H, m), 8.16 (1H, s), 8.83 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(7-methyl-2-oxoindolin-3-ylidene)acetohydrazide (3c)
% Yield: 73; IR (KBr): 3208, 1725, 1668, 1610, 695 cm-1. 1H-NMR: δ (ppm): 1.11 (3H, s), 4.75 (2H, s), 6.74-7.78 (7H, m), 8.18 (1H, s), 8.81 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-chloro-2-oxoindolin-3-ylidene)acetohydrazide (3d)
% Yield: 78; IR (KBr): 3207, 1720, 1667, 1607, 1006, 699 cm-1. 1H-NMR: δ (ppm): 4.78 (2H, s), 6.79-7.98 (7H, m), 8.18 (1H, s), 8.83 (1H, s)
2-(benzo[d]thiazol-2-ylthio)-N-(7-chloro-2-oxoindolin-3-ylidene)acetohydrazide (3e)
% Yield: 74; IR (KBr): 3212, 1721, 1664, 1609, 1004, 696 cm-1. 1H-NMR: δ (ppm): 4.80 (2H, s), 6.87-7.94 (7H, m), 8.20 (1H, s), 8.90 (1H, s). ).
2-(benzo[d]thiazol-2-ylthio)-N-(5-bromo-2-oxoindolin-3-ylidene)acetohydrazide (3f)
% Yield: 73; IR (KBr): 3215, 1732, 1668, 1608, 694, 611 cm-1. 1H-NMR: δ (ppm): 4.75 (2H, s), 6.98-7.98 (7H, m), 8.25 (1H, s), 8.84 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(7-bromo-2-oxoindolin-3-ylidene)acetohydrazide (3g)
% Yield: 70; IR (KBr): 3217, 1731, 1666, 1606, 695, 614 cm-1. 1H-NMR: δ (ppm): 4.77 (2H, s), 6.86-7.99 (7H, m), 8.15 (1H, s), 8.84 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-methoxy-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4a)
% Yield: 74; IR (KBr): 3320, 1730, 1692,), 1600, 694 cm-1. 1H-NMR: δ (ppm): 3.56 (3H, s), 3.82 (2H, s), 4.81 ( 2H, s), 6.83-7.91 (7H, m), 8.14 (1H, s), 8.70 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-methyl-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4b)
% Yield: 69; IR (KBr): 3323, 1730, 1692, 1602, 690 cm-1. 1H-NMR: δ (ppm): 1.12 (3H, s), 3.86 (2H, s), 4.74 (2H, s), 6.79-7.98 (7H, m), 8.17 (1H, s), 8.83 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(7-methyl-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4c)
% Yield: 71; IR (KBr): 3330, 1736, 1695, 1600, 691 cm-1.1H-NMR: δ (ppm): 1.14 (3H, s), 3.80 (2H, s), 4.72 (2H, s), 6.76-7.75 (7H, m), 8.18 (1H, s), 8.81 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-chloro-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4d)
% Yield: 77; IR (KBr): 3333, 1737, 1695, 1604, 1004, 693 cm-1. 1H-NMR: δ (ppm): 3.81 (2H, s), 4.73 (2H, s), 6.97-7.89 (7H, m), 8.33 (1H, s), 8.86 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(7-chloro-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4e)
% Yield: 71; IR (KBr): 3326, 1740, 1691, 1605, 1007, 691 cm-1. 1H-NMR: δ (ppm): 3.82 (2H, s), 4.84 (2H, s), 6.78-7.94 (7H, m), 8.20 (1H, s), 8.91 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(5-bromo-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4f)
% Yield: 73; IR (KBr): 3315, 1743, 1682, 1603, 689, 612 cm-1. 1H-NMR: δ (ppm): 3.89 (2H, s), 4.79 (2H, s), 6.89-7.89 (7H, m), 8.28 (1H, s), 8.89 (1H, s).
2-(benzo[d]thiazol-2-ylthio)-N-(7-bromo-2,4’-dioxospiro[indolin-3,2’-thiazolidin)-3’- yl)acetamide (4g)
% Yield: 75; IR (KBr): 3317, 1732, 1687, 1607, 690, 613 cm-1. 1H-NMR: δ (ppm): 3.84 (2H, s), 4.76 (2H, s), 6.68-7.91 (7H, m), 8.26 (1H, s), 8.87 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)5-methoxyspiro[indolin-3,5'-thiazolo[4,3-b][1,3,4]oxa diazol]-2-one (5a)
% Yield: 75; IR (KBr): 3330, 1690, 1610, 700 cm-1. 1H-NMR: δ (ppm): 3.58 (3H, s), 4.80 (2H, s), 6.85-7.94 (7H, m), 8.14 (1H, s), 8.76 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-5-methylspiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5b)
% Yield: 68; IR (KBr): 3343, 1720, 1691, 1612, 698 cm-1. 1H-NMR: δ (ppm): 1.15 (3H, s), 4.78 (2H, s), 6.77-7.96 (7H, m), 8.17 (1H, s), 8.84 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-7-methylspiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5c)
% Yield: 71; IR (KBr): 3340, 1726, 1694, 697 cm-1. 1H-NMR: δ (ppm): 1.16 (3H, s), 4.79 (2H, s), 6.75-7.76 (7H, m), 8.15 (1H, s), 8.85 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-5-chlorospiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5d)
% Yield: 70; IR (KBr): 3344, 1730, 1692, 1614, 1007, 702 cm-1. 1H-NMR: δ (ppm): 4.78 (2H, s), 6.95-7.86 (7H, s), 8.38 (1H, s), 8.84 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-7-chlorospiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5e)
% Yield: 75; IR (KBr): 3336, 1728, 1691, 1608, 1004, 705, cm-1. 1H-NMR: δ (ppm): 4.84 (2H, s), 6.76-7.94 (7H, m), 8.24 (1H, s), 8.96 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-5-bromospiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5f)
% Yield: 70; IR (KBr): 3335, 1735, 1689, 1613, 699, 615 cm-1. 1H-NMR: δ (ppm): 4.77 (2H, s), 6.89-7.87 (7H, m), 8.20 (1H, s), 8.89 (1H, s).
2'-((benzo[d]thiazol-2-ylthio)methyl)-7-bromospiro[indolin-3,5'-thiazolo[4,3- b][1,3,4]oxadiazol]-2-one (5g)
% Yield: 69; IR (KBr): 3337, 1730, 1697, 1610, 696, 613 cm-1. 1H-NMR: δ (ppm): 4.78 (2H, s), 6.67-7.97 (7H, m), 8.24 (1H, s), 8.86 (1H, s).
Pharmacology
All the newly synthesized compounds were studied for anti-inflammatory, analgesic and antibacterial activities and compared with reference drugs.
Anti-inflammatory activity
This study was done by following the procedure of Winter et al [16]. The rats were divided into three groups (control, test compounds and standard drug) of six animals each. A freshly prepared suspension of carrageenan (1% in 0.9% saline), 0.05 mL was injected under the planter aponeurosis of the right hind paw of each rat. The compound and standard drug were administered orally to the animals of drug treated groups and the standard drug group, respectively, 1h before the carrrageenan treatment with the help of a plethysmometer. The percent anti-inflammatory activity was calculated according to the formula given below.
Percentage of inhibition of oedema = 1-Vt/Vc) X 100
Where Vt and Vc are the volume of edema in drug, treated and control group, respectively.
Analgesic activity
The analgesic activity was performed by following the method of Berkowitz et al [17].
This method is based on the property of the test compound to antagonize the phenyl quinine- induced pain syndrome in mice. Groups of five mice injected interaperitoneally with 0.25 ml of a 0.02% solution of phenyquinone in ethanol (5%) 1 h after oral administration of the test compounds. The test number of writhes induced in each mouse was counted for 5 min (between 5 and 10 min) after injection of an irritant. The analgesic effect was expressed as percent protection in comparison to control.
% protection = (1-mean no. of writhes in mice of test group/mean number of writhes in mice of control group) x 100
Antibacterial activity
Antibacterial activity was determined by agar cup plate method [18] at a concentration of 100mg/ml using DMF as a solvent against the following organism- Escherichia coli, Staph.
Aureus, Klebsiella pneumoniae and B. sublitis. The zone of inhibition of each strain was recorded.
The activity has been compared with known standard drug ciprofloxacin at 10 μg/ml concentration. The biological results were analysed statistically by student‘t’ test. Propylene glycol treated group served as control.
Study of lipophilicity as a function of toxicity
The partition coefficient has been determined by measuring the concentration of the compound in two immiscible solutions according to the method of Hansch et al [19]. The partition coefficient is as follows:
P = C(octanol) / C(water)
The concentration of the compound in the two solutions was measured by photoelectric calorimeter. The hydrophobic constant (p) was evaluated by the method of Blaney et al. [20]
The substitutent constant for hydrophobic effect
π = log PX - log PH
Where PX = The partition coefficient of the substituted compounds PH = The partition coefficient of the unsubstituted compounds
The hydrophobic parameter (π) or Hansch ∑ π value was used and measure of hydrophobiicity is the sum of л for substitutent.
There is good correlation between the lipophilicity and toxicity of the drugs. The positive value of P (sum of π) suggests that compound is good from activity point of view. Moreover, it has been reported [21] that the compounds which are more lipid soluble possess more toxicity.
Acute toxicity
Acute lethal doses (ALD50) of all the compounds were investigated by the method of Smith Q.E. [22].
References
[1] D. J. Hadjipavlou-Litina, A. A. Geronikari, Drug design and discovery, 15(3), 199 (1998).
[2] B. H. M. Mruthyunjayaswami, B.K. Shanthaveerapa, Indian J Chem 39B, 433-439 (2000).
[3] I. Argyropoulou, A. Geronikaki, V. Paola, F. Zani, Arkivok VI: 89-102 (2009).
[4] F. Gualtiere, G. Brody, A. H. Fieldsteel, W. A. Skinner, J. Med. Chem. 14 (6), 546 (1971).
[5] P. Rani, V.K. Srivastava, A. Kumar, Eur J Med Chem, 39 449 (2004).
[6] A. Kumar, C.S. Rajput, S.K. Bhati , Bioorg Med Chem 15 (8): 3089 (2007).
[7] A. A. Mohamed, Radwash, E. Man, A. Regats, Normlen, M. Sabry and M. Sinam, E.L.
Shanwey Bioorg Med Chem 1 (11): 3832-3841 (2007).
[8] A. Kumar, S. Verma, B. Shetty, L.B. Nikam, R.P. Misra, S.K. Bhati, P. Kumar, C.S. Rajput, V. Singh, P. Rani, S. Rani, Yashowardhan, S. Singh, Oriental J Chem 22(2), 259 (2006).
[9] P. Jitendra, Suryavansi & N. R. Rai, Indian J. Chem. 45B (5): 1227-1230 (2006).
[10] M. K. Thaker, V.V. Kachadia, S.H. Joshi, (2003) Indian J Chem. 42B: 1544-1547.
[11] K. Bajaj, V.K. Srivastava, S. Lata, R. Chandra, A. Kumar, Kumar A Indian J Chem 42B, 1723-1728 (2003).
[12] N. J. Harib, J. F. Jurcak, D. E. Bregna, K. L. Burqher, H. B. Hartman, S. Kafka,
L. L. Kerman, S. K. ongsamut, J. E. Roehr, M. R. Szewczak, K. A. T. Woods, R.; Corbett;
Med. Chem. 39(20), 4044-4057 (1996).
[13] G. S. Gadaginamath, S. R. Pujar, R. R. Kavali, Indian J. Chem. 42B, 2023 (2003).
[14] Husain A, Ajmal M Acta Pharm. 59(2), 223 (2009).
[15] H. K. Misra, Archiv Der Pharmazie, 316, 487 (2006).
[16] C. A. Winter, E.A.Risley, G.W. Nuss, Proc. Soc. Exp. 111, 550-554 (1962).
[17] B. A. Berkowitz, S. A. D. Finck, S.H. Ngai, Pharmacol. Exp. Ther. 203, 539-547 (1977).
[18] D. Greenwood, R.C.B. Slack, J.F. Peutherer In; Medical Microbiology, 14th Edition. London, 1. (1992).
[19] C. Hansch, T. Fujita, J. Am. Chem. Soc. 86, 1616 (1964).
[20] J. M. Blaney, C. Hansch, C. Silipo, A. Vitoria. 84, 333, (1984).
[21] E. Hofsli, J. N. Meyer, Cancer Research, 50, 3997 (1990).
[22] Smith QE In: Pharmacological screening tests progress in medicinal chemistry, Butterworths, London 1, 1 (1960)
