INTRODUCTION:

The metabolic syndrome (MS) is diagnosed by a cluster of clinical parameters including central obesity, atherogenic dyslipidemia, raised blood pressure and hyperglycemia. Visceral obesity, hepatic steatosis and insulin resistance (IR) have been proposed as unifying mechanisms, yielding a pro-thrombotic and pro-inflammatory state¹. Type 2 diabetes mellitus (T2DM) is a long-term disease, characterized by a state of fasting hyperglycemia². Type 2 or adult onset diabetes is a chronic metabolic disorder defined by high levels of glucose in blood due to non-secretion of insulin. According to recent estimates, the world diabetic population could rise to 300 million by the year 2025 due to contemporary lifestyle and Obesity^3-4.

The conventional therapy of type 2 diabetes mellitus has not been satisfactory as it is not successful in treating associated risk factor, which is the major cause of morbidity. A current trend is, therefore, to make the therapy better by choosing appropriate combination of available drugs⁵. A parallel search for newer drugs is also being made. In recent years considerable activity in the pharmaceutical industry has led to the discovery of several chemical classes of antidiabetic agents. Many patent applications explain the intense interest in this field⁶.

Numerous examples of non-steroidal inhibitors have been disclosed; these include thiazole based compounds (I)⁷, sulfonamides (II)¹¹, adamantanyl triazoles and carboxamides among others (Fig. 1) ^6,9,10.

Compounds I and II belong to the arylsulfonamido (benzo)thiazoles class of 11β-HSD1 inhibitors^7,8. We choose these scaffolds as starting point to design the compounds prepared in this work.

MATERIAL AND METHOD:

Melting points of all compounds were determined in open capillaries and are uncorrected. TLC was performed on microscopic slides (2×7.5cms) coated with Silica-Gel-G and spots were visualized by exposure to iodine vapor. IR spectra of all compounds were recorded in KBr (Merck) on FT-IR 8400S Shimadzu spectrophotometer. Mass spectra were recorded on SHIMADZU LCMS 2010 EV Mass Spectrometer. 1H NMR spectra were obtained on BRUKER Advance-II 400 MHz instrument in DMSO as solvent and chemical shift were measured as parts per million downfield from tetramethylsilane (TMS) as internal standard.

METHOD OF SYNTHESIS

Synthesis of 2,4-thiazolidinedione (3) (Figure 2)

Solution containing Chloroacetic acid (1) (0.6 mol) in 60 mL of water and thiourea (2) (0.6 mol) dissolved in 60 mL of water were placed in 250 mL round-bottomed flask. The mixture was stirred for 15 min., followed by cooling to obtain white precipitates. To the content of the flask 60 mL of conc. HCl was added slowly from dropping funnel. The mixture was refluxed for 6 min. at 250 watt in microwave. On cooling the content of the flask solidified into a cluster of white needles. The product was filtered and washed with water to remove the trace of HCl and dried. The product was recrystallised from ethyl alcohol.

Synthesis of 5-benzylidene 2,4-thiazolidinedione (5) (Figure 2)

To a solution of benzaldehyde (4) (0.25 mol) and 2,4-thiazoidinedione (3) (0.25 mol) in hot glacial acetic acid (50 mL), fused sodium acetate (1.8 g) was added and then it was refluxed for 5 min. in microwave at 200 watt. Upon completion of the reaction, 300 mL of water was added and the precipitate obtained was filtered, washed with water and recrystallized from glacial acetic acid.

Synthesis of 4-((2,4-dioxothiazolidin-5-ylidene)methyl) benzene-1-sulphonyl chloride (7) (Figure 2)

Benzylidene 2,4-thiazolidinedione (5) (0.0388 mol) was placed in a 100 mL round bottom flask equipped with condenser and a dropping funnel. Chlorosulphonic acid (6) (0.155 mol) was added at room temperature using dropping funnel. The reaction was found to be exothermic. After addition of chlorosulphonic acid was over the reaction mixture was refluxed for 1 hr on a water bath. The reaction mixture was cooled and poured into a crused ice. The product was filtered and dried. The product was recrystallized from ethanol.

Procedure for Synthesis of 4-((2,4-dioxothiazolidin-5-ylidene)methyl)-substituted benzene sulphonamide (9) (Figure 2)

A mixture of 4-((2,4-dioxothiazolidin-5-ylidene)methyl)-benzene-1-sulfonyl chloride (7) (0.01 mol) and appropriate primary amine (8) (0.01 mol) were taken in a beaker and made a homogenous paste. The paste was exposed to microwave irradiation (200 watt) for 2-4 min., at interval of 30 seconds. After the completion of the reaction, ice-cold water was added to the reaction mixture and precipitated solid was separated by filtration, dried and recrystallized from ethanol.

In-Vivo Antidiabetic Activity

Oral glucose tolerance test

In-vivo study of synthesized compounds by OGTT

The oral glucose tolerance test (OGTT) measures the body's ability to use a type of sugar, called glucose that is the body's main source of energy. OGTT, a test of immense value and sentiment, in favour of using fasting plasma glucose concentration alone was seen as a practical attempt to simplify and facilitate the diagnosis of diabetes. Hyperglycemia is an important factor in the development and progression of the complications of diabetes mellitus.

Anti-diabetic activity

The anti-diabetic activity of newly synthesized 4-((2,4-Dioxothiazolidin-5-ylidene)methyl)Substituted Benzene Sulphonamide derivatives was carried out using Oral glucose tolerance test method.

Method: Oral glucose tolerance test

Animals used: Albino Wistar rat

No. of animals used: 6 (in each group)

Dose of std. drug: 30mg/kg (pioglitazone)

Route of administration: Oral

Group I: normal control group.

Group II: pioglitazone control group (30mg/kg)

Group-III-XII: were treated with synthesized compounds. The synthesized compounds were dissolved in suspension of 1% CMC.

Requirements:

Instruments: Glucometer.

Chemicals: 1% CMC

Standard drug: Pioglitazone (30 mg/kg) aq. solution was prepared using 1% CMC.

Test compounds: Solution of compounds was prepared and administered orally similar to that of standard drug.

Apparatus: feeding needles (for oral dosing), syringes (1ml, 2ml)

Experimental design and procedure

Albino Wistar rats weighing about 200-250 gm were taken for study. Group I served as a normal control group while Group II for pioglitazone control group. Group III-XII was treated with synthesized compounds. Special diets are fed for 30 to 90 days prior to the OGTT. We carry out the OGTT by fasting animals for 18 hours, taking a blood sample from the tail under local anesthesia and then gavaging with glucose solution (3gm/kg) of body weight. Blood samples are taken 30, 60, 90 and 120 minutes after the glucose meal and analyzed for blood glucose with a clinical glucometer. The reference drug and the synthesized compounds were administered orally with oral feeding tube to the rats. OGTT for non-diabetic rats were performed according to the standard method.

Group I stands for normal control group. Group II is treated with pioglitazone (30mg/kg body weight). The synthesized compounds were dissolved 1% CMC in according to 30mg/kg of body weight. Then the solution was administered orally to the glucose fed rats and blood was collected from the rat by cutting the tail. Blood sample was taken in a strip and then measured the glucose concentration level by glucometer and plasma glucose level in mg/dl was being monitored at 0, 30, 60 90, 120 minutes for six rats/group. Data were expressed as Mean ± Standard Error of Mean (SEM). Statistical comparisons were performed by one-way ANOVA followed by Dunnett's Multiple Comparison Test and the values were considered statistically significant when P <0.05.¹¹

RESULTS AND DISCUSSION:

Spectra for Synthesis of 4-((2,4-dioxothiazolidin-5-ylidene)methyl)-substituted benzene sulphonamide

4-(4-((2, 4-dioxothiazolidin-5-ylidene)methyl) phenylsulphonamido) benzoic acid (K11):

Mass m/z 405.3 [M+H]⁺; IR (cm^-1) 1750 and 1680 (C=O), 3000-3200 (Ar-CH), 1327, 1124 (-SO₂), 900 (SO₂NH), 3637 (OH); 1H NMR (ppm) d 1.8965(s, 1H, Ar-CH-); d 7.3108(s, 1H, -C=O-NH-C=O); d 7.3320(s, 1H, SO₂-NH-Ar); d 7.5155-8.0942(m, 8H, Ar-H); d12.5598 (s, 1H, -COOH)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-p-tolylbenzene sulphonamide (K12):

Mass m/z 374.9 [M]⁺; IR (cm^-1) 1736 and 1660 (C=O), 3000-3200 (Ar-CH), 1321, 1159 (-SO₂), 960 (SO₂NH), 2930 (CH Aliphatic); 1H NMR (ppm) d 1.8536(s,1H, Ar-CH-); d 2.5852(s, 3H, Ar-CH₃); d 6.9899(s, 1H, -C=O-NH-C=O); d 7.1922(s, 1H, SO₂-NH-Ar); d 7.2403-8.0945(m, 8H, Ar-H)

4-((2, 4-dioxothiazolidin-5-ylidene)methyl)- N-(4-chlorophenyl)-benzenesulphonamide (K13):

Mass m/z 394.4 [M]⁺; IR (cm^-1) 1754 and 1652 (C=O), 3000-3200 (Ar-CH), 1327, 1170 (-SO₂), 970 (SO₂NH), 893 (Ar-Cl); 1H NMR (ppm) d 1.8965(s, 1H, Ar-CH-); d 7.3108(s, 1H, -C=O-NH-C=O); d 7.3320(s, 1H, SO₂-NH-Ar); d 7.5155-8.0942(m, 8H, Ar-H)

4-((2, 4-dioxothiazolidin-5-ylidene)methyl)-N-(3-nitrophenyl)benzene sulphonamide (K14):

Mass m/z 406.7 [M+H]⁺; IR (cm^-1) 1760 and 1674 (C=O), 3000-3200 (Ar-CH), 1322, 1164 (-SO₂), 954 (SO₂NH), 1520 (NO₂); 1H NMR (ppm) d 1.9657(s, 1H, Ar-CH-); d 7.2474(s, 1H, -C=O-NH-C=O); d 7.3304(s, 1H, SO₂-NH-Ar); d 7.4870-8.1112(m, 8H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-(4-methoxyphenyl)benzenesulphonamide (K15): Mass m/z 390.6 [M]⁺; IR (cm^-1) 1754 and 1690 (C=O), 3000-3200 (Ar-CH), 1321, 1163 (-SO₂), 962 (SO₂NH); 1H NMR (ppm) d 1.9645(s, 1H, Ar-CH-); d 3.7839(s, 3H, -O-CH₃); d 6.9809(s, 1H, -C=O-NH-C=O); d 7.0401(s, 1H, SO₂-NH-Ar); d 7.2500-8.0795(m, 8H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-phenylbenzenesulphonamide (K16): Mass m/z 360.1 [M]⁺; IR (cm^-1) 1736 and 1660 (C=O), 3000-3200 (Ar-CH), 1321, 1159 (-SO₂), 960 (SO₂NH); 1H NMR (ppm) d 1.9657(s, 1H, Ar-CH-); d 7.2474(s, 1H, -C=O-NH-C=O); d 7.3128(s, 1H, SO₂-NH-Ar); d 7.4870-8.1148(m, 9H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-(4-hydroxyphenyl)benzenesulphonamide (K17): Mass m/z 376.8 [M]⁺; IR (cm^-1) 1770 and 1640 (C=O), 3000-3200 (Ar-CH), 1323, 1126 (-SO₂), 935 (SO₂NH), 3631 (OH); 1H NMR (ppm) d 1.9499(s, 1H, Ar-CH-); d 5.1922(s, 1H, Ar-OH); d 6.9809(s, 1H, -C=O-NH-C=O); d 7.0401(s, 1H, SO₂-NH-Ar); d 7.2500-8.0795(m, 8H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-o-tolylbenzenesulphonamide (K18): Mass m/z 375.5 [M+H]⁺; IR (cm^-1) 1736 and 1660 (C=O), 3000-3200 (Ar-CH), 1321, 1159 (-SO₂), 960 (SO₂NH), 2930 (CH Aliphatic); 1H NMR (ppm) d 1.8673(s, 1H, Ar-CH-); d 2.5861(s, 3H, Ar-CH₃); d 6.9880(s, 1H, -C=O-NH-C=O); d 7.0731(s, 1H, SO₂-NH-Ar); d 7.1922-8.4152(m, 8H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-(4-nitrophenyl)benzenesulphonamide (K19): Mass m/z 406.8 [M+H]⁺; IR (cm^-1) 1760 and 1674 (C=O), 3000-3200 (Ar-CH), 1322, 1164 (-SO₂), 954 (SO₂NH), 1520 (NO₂); 1H NMR (ppm) d 1.9543(s, 1H, Ar-CH-); d 7.2448(s, 1H, -C=O-NH-C=O); d 7.3217(s, 1H, SO₂-NH-Ar); d 7.4870-8.1121(m, 8H, Ar-H)

4-((2,4-dioxothiazolidin-5-ylidene)methyl)-N-(4-fluorophenyl)benzenesulphonamide (K20): Mass m/z 379.1 [M]⁺; IR (cm^-1) 1754 and 1652 (C=O), 3000-3200 (Ar-CH), 1327, 1170 (-SO₂), 970 (SO₂NH); 1H NMR (ppm) d 1.8977(s, 1H, Ar-CH-); d 7.3188(s, 1H, -C=O-NH-C=O); d 7.3240(s, 1H, SO₂-NH-Ar); d 7.5155-8.0958(m, 8H, Ar-H)

The series of 4-((2,4-dioxothiazolidin-5-ylidene)methyl)-substituted benzene sulphonamides contains 2,4-thiazolidinedione linker ring for binding with receptor site, central sulphonyl benzene ring as a linker and substitutes primary aromaric amines as a effectors region for maintaining lipophilicity of molecule. All the synthesized compounds were characterized by IR, Mass and 1H-NMR spectroscopy and report of them supports the structures of compounds.

Figure 3: Effect of Compounds K11-K20(at 30 mg/kg, Oral) on Glucose Excursion in OGTT of Albino Wistar Rats. Each Bar Represents Mean ± SEM (n=6)

Table 1: Physical properties of 4-((2,4-dioxothiazolidin-5-ylidene)methyl)-substituted benzene sulphonamide

Compound	Molecular formula	Mol. Wt.	% Yield	M.P.	Rf value
K11	C₁₇H₁₂N₂O₆S₂	404.42	65%	226-232^oC	0.44
K12	C₁₇H₁₄N₂O₄S₂	374.43	71%	198-201^oC	0.43
K13	C₁₆H₁₁N₂O₄S₂Cl	394.85	60%	222-224^oC	0.49
K14	C₁₆H₁₁N₃O₆S₂	405.41	66%	187-191^oC	0.51
K15	C₁₇H₁₄N₂O₅S₂	390.43	69%	170-175^oC	0.7
K16	C₁₆H₁₂N₂O₄S₂	360.41	77%	80-84^oC	0.40
K17	C₁₆H₁₂N₂O₅S₂	376.41	51%	264-270^oC	0.45
K18	C₁₇H₁₄N₂O₄S₂	374.43	74%	224-226^oC	0.56
K19	C₁₆H₁₁N₃O₆S₂	405.41	55%	200-206^oC	0.38
K20	C₁₆H₁₁N₂O₄S₂F	378.41	66%	108-116^oC	0.32

Mobile Phase= Hexane:Ethyl acetate (8:2)

Figure 4: Effect of Compounds K11-K20 (at 30 mg/kg, Oral) on AUC glucose (120 min*mg/dL) in OGTT of Albino Wistar rats. Each bar represents mean ± SEM (n=6)

Table 2: Effect of Compound K11-K20 (at 30 mg/kg, Oral) on AUC glucose (120 min*mg/dL) in OGTT of Albino Wistar rats.

Groups	AUC (0-120 min) glucose			Statistically Significance
Vehicle Control	14380	±	485.0773
Pioglitazone	12755	±	132.5707	*
Compound K11	14985	±	397.7122	Not significant
Compound K12	12840	±	1052.889	*
Compound K13	13905	±	257.3422	Not significant
Compound K14	14145	±	257.3422	Not significant
Compound K15	12805	±	272.8094	*
Compound K16	12900	±	2462.255	*
Compound K17	12290	±	801.2646	**
Compound K18	12160	±	1057.875	***
Compound K19	14105.000	±	229.5103	Not significant
Compound K20	13950.000	±	210.7131	Not significant

Each data set represents mean ± SEM (n=6) and data were analysed by One Way ANOVA followed by Dunnet’s multiple comparison t test where P<0.05 Vs vehicle control group.

All the synthesized compounds were screened for In Vivo anti diabetic activity by Oral Glucose Tolerance Test method against standard reference drug pioglitazone. Upon data shown in table 2 and figure 3 and 4, it can be said that, compounds K17 and K18 substituted with electron releasing 4-hydroxy and 2-methyl groups respectively, on aromatic lipophilic ring have shown most potent antidiabetic activity; while compounds K12, K15 and K16 containing 4-methyl, 4-methoxy and no substitution respectively, on aromatic ring have also shown good antidiabetic activity as compared to standard pioglitazone. It was noted that compounds possessing electron releasing substitution at 2^nd and/or 4^th position on aromatic ring of lipophilic region shows promising antidiabetic activity. 4-chloro and 4-fluoro substituted compounds K13 and K20 have also shown antidiabetic activity. The remaining compounds K11, K14 and K19 substituted with electron withdrawing 4-carboxyl, 3-nitro and 4-nitro respectively, on aromatic ring have shown less antidiabetic activity as compared to pioglitazone.

CONCLUSION:

Looking at the results, it revealed that compounds containing thiazolidinedione ring have better antidiabetic activity because of structural similarity towards PPARγ receptors. It was also noted that 2,4-thiazolidinediones having more lipophilic moieties have exhibited more potent antidiabetic activity, so it is concluded that 2, 4-thiazolidinedione compounds containing more lipophilic group increases antidiabetic activity.

ACKNOWLEDGEMENT:

We are grateful to the management of Shree S. K. Patel College of Pharmaceutical Education and Research for encouragement and providing laboratory facility. We are also thankful to sophisticated analytical instrumentation facility department, Punjab University for analytical support.

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Received on 16.02.2015 Accepted on 03.03.2015

Asian J. Res. Pharm. Sci. 5(1): Jan.-March 2015; Page 1-7

DOI: 10.5958/2231-5659.2015.00001.6