Synthesis and Pharmacological Activity of Some 2-[6-(Phenyl) 2-Thio 1,3-Oxazin-3yl] Amino Benzothiazole Derivatives
2Professor, J. L. Chaturvedi College of Pharmacy, Nagpur – 440016, India.
*Corresponding Author E-mail: jsgunja@gmail.com, ajasnani7@gmail.com
ABSTRACT:
Some new hydrazino group substituted benzothiazole derivatives have been synthesized and their characterization were identified on the basis of melting point range, Rf values, IR and 1H NMR spectral analysis. The derivatives were screened for anti-inflammatory (Carrageenan-induced paw edema test in rats), analgesic (Hot plate method) and anticonvulsant (Electric shock method) activities inflammatory, analgesic and anticonvulsant activities. The derivatives exhibited significant to moderate anti-inflammatory analgesic and anticonvulsant activities.
KEYWORDS: Hydrazino, Benzothiazole, Anti-inflammatory activity, Analgesic activity, Anticonvulsant activity.
1. INTRODUCTION: [1-6]
Their characterization was done by spectroscopic methods. Research in this area is still unexplored, therefore the present study is directed towards the synthesis of novel derivatives of benothiazole with good yield and enhance anti-inflammatory, analgesic and anticonvulsant activities.
2. METHODS AND MATERIALS[7-14]:
Reagents grade chemicals were used without further purification. All the melting points were taken in open capillaries and are uncorrected. The purity of the synthesized derivatives was checked by Thin Layer Chromatography.
2.1 Synthesis of substituted 2-hydrazinyl 1, 3-benzothiazole:
Take equimolar amount of substituted aniline and conc. hydrochloric acid and triturate it thus solid of salt of Aniline hydrochloride obtained. Mix aniline hydrochloride salt and sulphur into 1:3 proportion respectively stir it continuously by addition of equivalent amount of carbon disulphide in KOH and add 15-20ml of ethanol, reflux it for 5hrs 2-mecaptobenzothiazole obtained, recrystallize with methanol. Take equimolar of 2-mecaptobenzothiazole and hydrazine hydrochloride and add 10-15ml of ethanol stir it and heat mixture at 150-155°C temperature for 2-3hrs, solid mass was obtained which recrystallize from ethanol, to get substituted 2-hydrazinyl 1,3-benzothiazole derivatives.
2.2 Synthesis of 2-[6-(phenyl) 2-thio 1,3-oxazin-3yl] amino benzothiazole derivatives:
Take equimolar amount of substituted 2-hydrazinyl 1,3-benzothiazole derivatives and substituted acetophenone in methanol, add 2-4ml of formaldehyde and add few drops of conc. hydrochloride acid with constant stirring and reflux for 2hrs cooled and recrystallize with methanol to get 3-[substituted benzothiazole] hydrazino-1-substituted phenyl propan-1-one. In this add equal amount of sodium borohydride in methanol and constantly stir for 3hrs, stand for overnight, thus solid of 3-[substituted benzothiazole] hydrazino-1-substituted phenyl propan-1-ol gets separated recrystallize with methanol. Take solution 3-[substituted benzothiazole] hydrazino-1-substituted phenyl propan-1-ol in dry chloroform and 2-3ml of carbon disulphide was added dropwise. The resulting mixture was refluxed for 7hrs and distilled-off the excessive solvent. Recrystallized the residue obtained with methanol to get2-[6-(phenyl) 2-thio 1,3-oxazin-3yl] amino benzothiazole derivatives.
Table 1: Physical data of synthesized compounds
|
Compounds Code |
R1 |
R2 |
Melting Point |
Rf Value |
% Yield |
|
sc-1 |
-H |
-OH |
192-194 |
0.57 |
60.4 |
|
sc-2 |
-2Cl |
-4NH2 |
201-203 |
0.69 |
65.5 |
|
sc-3 |
-2Cl |
-H |
232-234 |
0.75 |
58.0 |
|
sc-4 |
-4Br |
-4OH |
202-204 |
0.85 |
40.5 |
|
sc-5 |
-4Br |
-H |
175-177 |
0.45 |
58.5 |
|
sc-6 |
-4NO2 |
-4NH2 |
166-168 |
0.35 |
73.5 |
|
sc-7 |
-4NO2 |
-4OH |
233-235 |
0.84 |
72.5 |
2.3 Spectroscopic study:
The characterization of synthesized compounds was done by IR, NMR and MASS spectral data.IR spectra were scanned on Shimadzu FTIR-8400 Spectrophotometer in frequency range of 4000-400cm-1 by KBr-DRS method. 1H NMR spectral was recorded in DMF with tetramethylsilane (TMS) as the internal standard at 400 MHz on a BRUKER ACF-400 spectrophotometer. The chemical shifts are reported as parts per million (ppm). The mass spectra of synthesized compounds were recorded by GCMS-Shimadzu-QP2010.
2-[6-(4-Hydroxyphenyl) 2-thio1,3-oxazin-3yl] aminobenzothiazole (GS-1):
IR (KBr) (cm-1); 1612.13(ArC=C), 1665.7 and 3402.54 (N-H), 3064.98 and 1456.23(ArCH), 1254.46(C=S), 1779.0(C=O), 3650(CH-OH).
1H NMR (400 MHz) (δppm); 3.69-3.71 (t,4H-CH2), 2.59-2.61 (t, 4H-CH2), 3.33 (s, 2H-CH2), 9.15 (s, 1H-NH), 7.66-7.69 (q, 1H, Ar-H), 7.61-7.64 (dd, 1H, Ar-H), 7.13-7-18 (m, 1H, Ar-H), 1.8 (H-CH2-OH).
Mass, m/z; 295 (M+).
2-[6-(4-Aminophenyl) 2-thio1,3-oxazin-3yl] amino 4-chloro benzothiazole (GS-2):
IR (KBr) (cm-1); 3253.09 and1600.97 (N-H), 3078.97and 1452.48 (Ar-CH), 1256.81 (C-N), 1358.0 (C=S), 1632.38 (C=O),1535.39 (ArC=C), 668.31 (H-CH2-Cl).
1H NMR (400 MHz) (δ ppm); 3.68-3.61 (t,4H-CH2), 3.01-3.05 (t, 4H-CH2), 3.12 (s, 2H-CH2), 8.96 (s, 1H-NH), 7.68-7.79 (q, 1H, Ar-H), 6.91-6.94 (dd, 1H, Ar-H), 7.63-7-08 (m, 1H, Ar-H), 2.1 (H-NH), 3.0-3.02 (H-CH2-Cl).
Mass, m/z; 370 (M+).
2-[6-(Phenyl) 2-thio 1,3-oxazin-3yl] amino 6-bromo benzothiazole (GS-3):
IR (KBr) (cm-1); 3321.08 and1613.23 (N-H), 3099.97and 1398.48 (Ar-CH), 1358.81 (C-N), 1396.10 (C=S), 1701.38 (C=O),1536.39 (ArC=C), 779.01 (H-CH2-Br).
1H NMR (400 MHz) (δ ppm); 3.73-3.76 (t,4H-CH2), 2.98-3.01 (t, 4H-CH2), 2.91 (s, 2H-CH2), 9.12 (s, 1H-NH), 6.98-7.04 (q, 1H, Ar-H), 6.87-6.92 (dd, 1H, Ar-H), 7.83-7-11 (m, 1H, Ar-H), 3.3-3.51 (H-CH2-Cl).
Mass, m/z; 293 (M+).
2-[6-(4-Bromophenyl) 2-thio1,3-oxazin-3yl] amino 6-bromo benzothiazole (GS-4):
IR (KBr) (cm-1); 3252.09 and 1600.87 (N-H), 3068.98and 1454.54 (Ar-CH), 1300.10 (C-N), 1a296.10 (C=S), 1631.38 (C=O),1525.38 (ArC=C), 778.01 (H-CH2-Br), 3401.23(CH-OH).
1H NMR (400 MHz) (δ ppm); 3.34-3.36 (t,4H-CH2), 2.77-2.83 (t, 4H-CH2), 3.51 (s, 2H-CH2), 11.26(s, 1H-NH), 6.98-7.04 (q, 1H, Ar-H), 7.50-7.62 (dd, 1H, Ar-H), 6.83-6-11 (m, 1H, Ar-H), 3.5-3.81 (H-CH2-Br), 1.8 (H-CH2-OH). Mass, m/z; 428 (M+).
2-[6-(Phenyl) 2-thio1,3-oxazin-3yl] amino 6-chloro benzothiazole (GS-5):
IR (KBr) (cm-1); 3357.09 and 1608.87 (N-H), 3068.98and 1454.54 (Ar-CH), 1305.85 (C-N), 1319.19 (C=S), 1681.38 (C=O),1562.39 (ArC=C), 698.01 (H-CH2-Br), 3410.23(CH-OH).
1H NMR (400 MHz) (δ ppm); 3.20-3.36 (t,4H-CH2), 2.87-2.98 (t, 4H-CH2), 3.37 (s, 2H-CH2), 11.56(s, 1H-NH), 7.98-8.04 (q, 1H, Ar-H), 7.60-7.72 (dd, 1H, Ar-H), 7.83-6711 (m, 1H, Ar-H), 3.5-3.71 (H-CH2-Cl), 2.0 (H-CH2-OH).Mass, m/z; 298 (M+).
2-[6-(4-Aminophenyl) 2-thio1,3-oxazin-3yl]amino 6-nitro benzothiazole (GS-6):
IR (KBr) (cm-1); 3254.19 and1600.87 (N-H), 3108.97and 1452.48 (Ar-CH), 1256.81 (C-N), 1368.0 (C=S), 1632.38 (C=O),1536.49 (ArC=C).
1H NMR (400 MHz) (δ ppm); 3.01-3.06 (t,4H-CH2), 4.01-4.05 (t, 4H-CH2), 3.16 (s, 2H-CH2), 8.96 (s, 1H-NH), 7.58-7.69 (q, 1H, Ar-H), 7.01-7.04 (dd, 1H, Ar-H), 7.96-7-18 (m, 1H, Ar-H), 2.1 (H-NH), 5.2-5.4 (H-CH2-NO2).
Mass, m/z; 287 (M+).
2-[6-(4Hydroxyphenyl) 2-thio1,3-oxazin-3yl] amino 6-nitro benzothiazole (GS-7):
IR (KBr) (cm-1); 1612.13 (ArC=C), 1665.7 and 3368.54 (N-H), 3164.98 and 1456.23 (ArCH), 1301.01 (C-N), 1254.46 (C=S), 1669.0 (C=O), 3450 (CH-OH).
1H NMR (400 MHz) (δ ppm); 3.59-3.68 (t,4H-CH2), 2.79-2.84 (t, 4H-CH2), 3.53 (s, 2H-CH2), 10.15 (s, 1H-NH), 7.76-7.80 (q, 1H, Ar-H), 7.61-7.64 (dd, 1H, Ar-H), 7.13-7-18 (m, 1H, Ar-H), 1.8 (H-CH2-OH).
Mass, m/z; 295 (M+).
3. PHARMACOLOGICAL ACTIVITY:
All the synthesized compounds have been screened for in-vitro anti-inflammatory, analgesic and anticonvulsant activities against rats and mice by Carrageen paw edema method, Hot plate method and Electric shock method using different standard drug for respective activity.
3.1: Anti-inflammatory activity[15-17]:
The experiment was carried out using Carrageenan induced paw edema method with minor modification. The experiment was carried on Wistar albino rats of either sex weighing between 100-200g. The standard drug and synthesized compounds were dissolved in minimum quantity of 2% solution of tween 80. The final concentration of tween 80 in all solution was less than 2.5%. Test Solution containing different concentrations of the drug was prepared with tween 80. To induce paw edema in sub planter region, 1% solution of carrageanan solution was prepared. Percentage of Inhibition of inflammation was calculated from the control where no drug was added. The diclofenac sodium was used as a standard drug. The percentage inhibition of inflammation was calculated by using following a formula. (Table 2)
% of Inhibition =1-[a-x/b-y} * 100
Where, a = paw thickness of test group after 5h carrageenan injected
x = paw thickness of test group initially
b = paw thickness of control group after 5h carrageenan injected
y = paw thickness of control group initially
3.2: Analgesic activity[15,16,18]:
Pain awareness was measured by nerve ending receptors in peripheral tissues and transmitted to the central nervous system by primary afferent fibres to the brain. Transmission can be reduced by drug acting on several different neurotransmitter or completely prevented by blocking the sodium channels required for conduction in the afferent neuron axon outside or inside spinal column. The experiment was carried on Wistar albino mice. The standard drug and synthesized compounds were dissolved in minimum quantity of 2% solution of tween 80. The final concentration of tween 80 in all solution was less than 2.5%. Test Solution containing different concentrations of the drug was prepared with tween 80. The jumping and liking was noted in 0min, 90min (Table 3). The tramadazol was used as a standard drug. The percentage inhibition in analgesic activity was evaluated using the following a formula.
% Inhibition =
[1-(before treatment/ after treatment)] x 100
3.3: Anticonvulsant activity[15,16,19,20]:
The electroshock assay in rat was used primarily as an indication for compounds which were effective in grand mal epilepsy. Tonic hind limb extension was evoked by electric stimuli which were suppressed by antiepileptics but also by other centrally acting drugs. After 1hrs. all animals received shock and the convulsions were induced. The duration of extensor tonus was noted. The complete abolition of hind leg tonic extension or reduction time was noted. The onset action and duration of action were recorded (Table 4). The phynetoin sodium was used as a standard drug. The percentage inhibition of convulsion was calculated by following formula.
%Inhibition = [c-t/c ]x 100
Where,
t = reading of the test group(drug treated)
c = reading of control group
4. RESULTS AND DISCUSSION:
The purpose of the present work was to synthesize a series of desired title compounds 2-[6-(phenyl) 2-thio 1,3-oxazin-3yl] amino benzothiazole (sc1-sc7) by reacting hydrazine hydrochloride and substituted 2-mercaptobenzothiazole. Furthermore, the procedure used commercially available reagents, giving the desired compounds in moderate yields (45-75%). The versatility of this methodology makes it suitable for library synthesis in drug discovery efforts. The synthesized derivatives was estimated by physicochemical properties. The melting point of all derivatives were sharp and Rf value was also determine by using methanol: acetonitrile (9:1) as solvent for their homogeneity shown in Table 1.
The synthesized compounds exhibit anti-inflammatory, analgesic, anticonvulsant activity. Synthetic compounds sc-2, sc-3, sc-4, sc-5 have shown significant anti-inflammatory activity, synthetic compounds sc-1, sc-3, sc-4, sc-5 have shown significant analgesic activity and also promising anticonvulsant activity shown by synthetic compounds sc-2, sc-3, sc-4, sc-6, sc-7 Compounds sc-3 and sc-4 was most significant. We were pleased to observe significant activity of compound compounds sc-1, sc-2, sc-6, sc4-7 activity when compared with standard drug. While the anti-inflammatory, analgesic, anticonvulsant activity studies have shown in table 2, 3, 4 respectively.
Table 2: Anti-inflammatory Activity of Synthetic Compound
|
Sr. No. |
Compound Code |
% Inhibition |
|
01 |
STD |
80.00 |
|
02 |
Sc-1 |
49.08 |
|
03 |
Sc-2 |
69.00 |
|
04 |
Sc-3 |
74.00 |
|
05 |
Sc-4 |
78.00 |
|
06 |
Sc-5 |
64.00 |
|
07 |
Sc-6 |
52.00 |
|
08 |
Sc-7 |
50.00 |
Fig 1: Anti-inflammatory Activity of synthetic compound against standard diclofenac
Table 3: Analgesic Activity of Synthetic Compounds
|
Sr. No. |
Compound Code |
% Inhibition |
|
01 |
STD |
65.91 |
|
02 |
Sc-1 |
52.08 |
|
03 |
Sc-2 |
43.06 |
|
04 |
Sc-3 |
62.76 |
|
05 |
Sc-4 |
61.54 |
|
06 |
Sc-5 |
57.02 |
|
07 |
Sc-6 |
41.31 |
|
08 |
Sc-7 |
53.03 |
Fig 2: Analgesic Activity of synthetic compound against standard Tramadazole
Table 4: Anticonvulsant Activity of Synthetic Compounds
|
Sr. No. |
Compd. Code |
% Inhibition |
|
01 |
STD |
88.99 |
|
02 |
Sc-1 |
47.08 |
|
03 |
Sc-2 |
79.16 |
|
04 |
Sc-3 |
82.65 |
|
05 |
Sc-4 |
84.54 |
|
06 |
Sc-5 |
54.02 |
|
07 |
Sc-6 |
83.93 |
|
08 |
Sc-7 |
80.03 |
Fig 3: Anticonvulsant Activity of Synthetic Compounds against standard Phenytoin sodium
6. CONCLUSION:
Various benzothiazole derivatives having hydrazinyl substituents and different substituents at position 4 and position 6 of electronegative atoms were synthesized with a view of enhancing the Pharmacological activity. The structure of newly synthesized compounds was confirmed by IR, 1NMR, Mass spectra. Further evaluation of pharmacological activity was carried out. The synthesis of various substituted 2-[6-(phenyl) 2-thio 1,3-oxazin-3yl] amino benzothiazole derivatives by the described method resulted in products with good yield. Pharmacological evaluation of the synthesized compounds showed good to moderate activity.
7. ACKNOWLEDGEMENT:
The authors are thankful to the authorities of J. L. Chaturvedi college of Pharmacy, Govt. Veterinary College, Sharad Pawar College of Pharmacy, Nagpur, Maharashtra, India, and SAIF University Punjab, Chandigarh, India for providing necessary facilities and carrying out IR, NMR, Mass spectra.
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Received on 16.02.2019 Modified on 18.03.2019
Accepted on 21.04.2019 © RJPT All right reserved
Research J. Pharm. and Tech. 2019; 12(6): 2857 -2861.
DOI: 10.5958/0974-360X.2019.00481.5