Design, Synthesis, Characterization and Antioxidant activity of Novel Benzothiazole and Coumarin based 6-(3, 5-dimethylpyrazol-1-yl) pyridazin-3-one Derivatives

 

Ranjit V. Gadhave^1,2*, Bhanudas S. Kuchekar^1,2

¹Department of Pharmaceutical Chemistry, MAEER’s Maharashtra Institute of Pharmacy, Kothrud,

Pune - 411038, Maharashtra, India.

²School of Pharmacy, MIT World Peace University, Kothrud, Pune - 411 038, Maharashtra, India.

 

ABSTRACT:

The present work describes biological evaluation of target molecules designed by molecular docking with 4h1j protein using Autodock Vina docker. Designed novel benzothiazole and coumarin based 6-(3, 5-dimethylpyrazol-1-yl) pyridazin-3-one derivatives were synthesized by condensation of substituted 6-(3,5-dimethylpyrazol-1-yl)pyridazin-3(2H)-one with substituted 2-amino benzothiazoles, substituted 2-oxo-2H-chromene-3-carbonyl chloride or 4-(bromomethyl)-2H-chromen-2-one. Synthesized compounds were characterized by spectral analysis and screened for antioxidant activity using 1, 1-diphenyl-2-picrylhyrazyl radical scavenging, Hydrogen peroxide scavenging and ferric reducing antioxidant power method. The compounds 5c and 9b showed more antioxidant potential and other compounds showed moderate to less activity as compared to standard Ascorbic acid and Butylated hydroxyl toluene.

 

 

 

INTRODUCTION:

Among various heterocycles pyridazine, pyrazole, benzothiazole and coumarin are component of several drug molecules with variety of biological activities. Pyridazine derivatives possess many biological activities like analgesic¹, cardioprotective¹,anti-inflammatory^1,2, antinociceptive², smooth muscle relaxant², anticancer³, AChE inhibitor⁴, antiviral⁵,anticonvulsant⁶, antioxidant⁷ and antimicrobial⁷. Pyrazole derivatives possess biological activities like anti-inflammatory^8,9, antioxidant^8,10, antimicrobial^8,11, anticovulsant¹¹, antiviral¹², antileishmanial¹³, anticancer¹⁴ andantifungal¹⁵. Benzothiazole derivatives possess biological activities like antimicrobial¹⁶, analgesic^16,20, antiviral¹⁷, anticancer^17,18, antifungal¹⁹ and antioxidant²¹.Coumarin derivatives possess biological activities like anticancer²², antimalarial²², MAO Inhibitor²³, anti-inflammatory²⁴ and antioxidant²⁵.

 

The diversified biological activities of pyridazine, pyrazole, benzothiazole and coumarin derivatives attracted further derivatization and their biological evaluation. The condensations products of these heterocycles possess various types of biological activities like antibacterial^26,27, antioxidant²⁷, antiviral²⁸and anticancer²⁹.

 

Imbalance of the prooxidant-antioxidant homeostatic phenomenon in the body leads to many diseases³⁰. Excessive free radicals generation occurs due to oxidative stress or poor scavenging due to depletion of the dietary antioxidants. It is very much essential to design antioxidants to prevent development of related chronic diseases³¹.

 

The present work is extension of efforts for design and development newly synthesized benzothiazole and coumarin based pyridazinone derivatives as a potential lead for antioxidant activity.

 

MATERIAL AND METHODS:

All reported organic compounds were synthesized using laboratory grade chemicals. All reactions were monitored by TLC and melting point. TLC (Type 60 GF254, Merck) were used to check purity of compounds and visualization was done by iodine vapours and UV-Lamp. Melting points determined by VEEGO (Model: VMP-D) temperatures are expressed in °C. Compound purified by flash chromatography (Combiflash Companion) and recrystallization. IR spectral study by Jasco FT/IR-4600 using KBr disc prepared by pressed pellet technique. Mass spectra recorded on Impact HD QTOF Mass Spectrophotometer (Bruker-GmbH) with resolution 40,000 (m/z 1522). ¹H-NMR spectral study by Bruker Advance III HD 500 MHz NMR Spectrometer (DMSO-d6, TMS). Elemental analysis on Bruker Electron Microscope Analyzer and values obtained were within ± 0.04% of the calculated values. Absorbance was measured using UV-VIS Spectrophotometer (Varian Carry100).

 

Molecular Docking Study:

Molecular docking study of library of logically designed molecules was carried out with protein data base co-crystallized complexed (Code: 4h1j) using Autodock Vina docker in order to determine probable binding capability of ligand for active site. The active sites were identified as amino residuesAsp567A, Glu474A, Leu556A, Met478A, Lys457A, Tyr505A, His547A and Phe568A to be interacting with ligand molecule and to define docking site for ligand. Designed molecules were then docked with selected cavity of the crystallized target protein structure to check the affinity and ranked according to their docking score based on negative lowest binding energy (Table-I). The first lowest binding energy poses are selected for analysis of docking results and analyzed for various intermolecular interactions. Designed molecules were selected for synthesis considering the binding interactions and binding energies.

 

Chemistry:

In designing of synthetic protocol for target molecules, it was envisaged that substituted pyrazolopyridazinone (3) represents interesting intermediates for synthesis. The synthetic strategy adopted is depicted in figure 1. Intermediate 3 was synthesized from corresponding 3-chloro derivative (2), synthesized from acetyl acetone and 2(6-chloropyridazin-3-yl) hydrazine (1), which in turn was obtained from 3, 6-dichloropyridazine. Titled target derivatives were synthesized from 3 and substituted 2-amino benzothiazoles (5a-c and 9a-c), Substituted coumarin-3-formyl chloride (10a-c) or 4-(bromomethyl)-chromen-2-one (11a-c).

 

 

Fig.1: General Scheme for Synthesis of Compounds

 

Reaction conditions:

A. NH₂NH_2, Stirred, 40°C, 6h; b. Acetyl acetone, Stirred, 60°C, 5h; c.  Sodium acetate, GAA, 90°C, 5h; d. K₂CO₃ in DMF, chloroacetylchloride, Stirred, 35°C, 2h;e. K₂CO₃ in DMF, Substituted benzothiazole, Stirred, 100°C, 4-6h; f. K₂CO₃ in DMF, ethylbromoacetate, Stirred, 30°C, 2h; g. 10% NaOH, heat, 3h; h. Thionyl Chloride, reflux, 1h; i. K₂CO₃ in DMF, Substituted benzothiazole, Stirred, 80°C, 2-5h; j. Substituted coumarin-3-formyl chloride, K₂CO₃ in DMF, 100°C, 2-4h; k. Substituted 4-(bromomethyl)coumarin, K₂CO₃ in DMF, 100°C, 3-5h.

Synthesis of 1:

3, 6-dichloropyridazine (0.02mol) was placed in 25mL ethanol. Add hydrazine hydrate (0.06mol) dropwise at RT and stirred for 6h at 40°C. Cooled to get precipitate of title compound. Yield: 78%, m.p.: 104-108°C and Rf: 0.45 (Toluene: Ethyl Acetate (EA)) (3:1)

 

Synthesis of 2:

Placed1(0.01mol) in 30 mL methanol and acetylacetone (0.01mol) added slowly, heated at 60°C for 5h. Kept overnight at RT and precipitate obtained was filtered to obtain title compound. Yield:72%, m.p.:113-116°C and Rf: 0.79 (Toluene: EA) (3:1)

 

Synthesis of 3:

Placed 2 (0.015mol) and sodium acetate (0.022mol) in GAA, stirred at 90°C for 5h. Cooled, dumped on ice (60 mL), and obtained precipitate as title compound. Yield: 76%, m.p.: 253-256 °C and Rf: 0.4 (Toluene: Methanol) (3:1)

 

Synthesis of 4:

Place3 (0.01mol) and K₂CO₃ (0.03mol) in DMF, added chloroacetyl chloride (0.015) slowly at 5°C and stirred further for 2h at 35°C. Cooled, excess DMF was removed by vacuum distillation, poured on ice (40mL), extracted with ethyl acetate to get title compound. Yield: 71%, m.p.: 118°C and Rf: 0.45 (Toluene: EA) (3:1)

 

Synthesis of 5a-c:

Placed 4(0.01 mol), substituted 2-aminobenzothiazole (0.11 mol) and K₂CO₃(0.03 mol) in DMF, stirred at 100°C for 4-6h. Cooled and poured on ice (50mL) and the precipitates obtained as title compounds.

5a: Yield:77%, m.p.:124°C and Rf:0.60 (Toluene: EA) (3:1); 5b: 69%, 162°C, 0.54; 5c: 81%, 152°C and 0.58.

 

Synthesis of 6:

Placed 3(0.012mol) and K₂CO₃(0.06 mol) in DMF, ethylbromoacetate (0.015) was added dropwise and stirred at 30° for 2h. Cooled and dump on crushed ice (75mL) and obtained precipitate as title compound. Yield: 74%, m.p.: 82-85°Cand Rf: 0.45 (Toluene: Methanol) (3:1)

 

Synthesis of 7:

Placed 6 (0.01mol) in 10% NaOH (0.02mol) and heated for 3h. Cooled, acidified to precipitate out title compound. Yield: 94°C, m.p.: 184°C and Rf: 0.72 (Toluene: Methanol) (3:0.7)

 

Synthesis of 8:

Solution of 7(0.01mol) in thionyl chloride (0.04mol) was refluxed for 1h. Excess thionyl chloride was distilled out by vacuum distillation and residues were collected as title compound. Yield: 59%, m.p.: 109°C and Rf: 0.70 (Toluene: EA) (3:1)

Synthesis of 9a-c:

Placed 8(0.01mol), substituted 2-aminobenzothiazole (0.11 mol) and K₂CO₃(0.03 mol) in 40 mL DMF, stirred at 80°C for 2-5h. Cooled, poured on ice (50mL) and obtained precipitate as title compounds.

9a: Yield:72%, m.p.:146°C and Rf:0.60 (Toluene: EA) (3:1); 9b: 81%, 173°C, 0.68: 9c: 66%, 154°C, 0.56.

 

Synthesis of 10a-c:

Placed 3(0.01 mol)), Substituted coumarin-3-formyl chloride (0.11 mol) and K₂CO₃(0.03 mol) in 40 mLDMF was stirred at 100°C for 2-4h. Cooled, poured on ice (80 mL) and obtained precipitate as title compounds.

10a: Yield:81%, m.p.:212°C and Rf:0.42 (Toluene: EA) (3:1); 10b: 71%, 164°C, Rf:0.50; 10c: 74%, 188°C, 0.44.

 

Synthesis of 11a-c:

Placed 3(0.01 mol)), Substituted 4-(bromomethyl) coumarin (0.11 mol) and K₂CO₃(0.03 mol) in 40 mLDMF was stirred at 100°C for 3-5h. Cooled, poured on ice (50 mL) and obtained precipitate as title compounds.

11a: Yield:72%, m.p.:148°C and Rf:0.57 (Toluene: EA) (3:2); 11b: 56%, 224°C, 0.66; 11c: 60%, 126°C, Rf:0.64.

 

Synthesized compounds were purified using flash chromatography (Silica, Dichloromethane-Methanol), column chromatography (Silica gel, Toluene: Ethyl acetate: Methanol) and recrystallized using suitable solvents. Benzene dried compounds were used for spectral analysis.

 

Antioxidant Activity:

Antioxidant activity performed using following in-vitro methods and results are summarized in table II.

 

DPPH Scavenging Method^{32, 33, 34, 35, 36}:

The antioxidant potential of synthesized compounds was evaluated as per method described by Venkatachalam H. et al. and Stefania-Felicia Barbuceanu et al. with slight modifications. DPPH (2mL, 400µM) in methanol mixed with test compound solutions 50, 100, 150, 200, 250 and 500µM in methanol. The samples incubated for 20 minute and absorbance measured at 517nm. Ascorbic acid (AA) and Butylated Hydroxy Toluene (BHT) were used as standards for comparison.

                                                 Abs. Blank-Abs. Test

DPPH Scavenging effect (%) = ––––––––––––––– × 100

                                                         Abs. Blank

 

IC₅₀ reported was calculated from a plot between sample concentration and% scavenging.

 

H₂O₂ Scavenging Method³⁷:

H₂O₂ scavenging activity evaluated as per method described by Ruch et al. with slight modifications.H₂O₂ solution (40µM) and 3.4mL solution (50, 100, 150, 200, 250 and 500µM) of test compounds in phosphate buffer (pH 7.4) mixed with 40µM H₂O₂ solution (0.6mL). Absorbance measured after 10 minute at 230nm. AA and BHT were used as standards for comparison.

                                                

 

                                           Abs. Blank-Abs. Test

H₂O₂ Scavenging effect (%) = ––––––––––––––– × 100

                                                      Abs. Blank

 

FRAP Method^{38, 39}

The antioxidant power was determined using Oyaizu et al. method with slight modifications. Method determines capacity of test compound to reduce the ferric to ferrous- ferricyanide complex. Different dilutions of samples are prepared (50, 100, 150, 200, 250 and 500µM) in 1mL methanol and diluted with phosphate buffer (pH 6.6, 2.5 mL) and potassium ferricyanide (2.5mL1%). Incubated for 20 min at 45-50°C. Aliquots of trichloroacetic acid (2.5mL, 10% w/v) were added, mixed upper layer (2.5 mL) with 2.5mL DW and ferric chloride (0.5mL, 0.1%). Reducing power was determined from absorbance at 700 nm and AA and BHT were used as standards for comparison.

 

RESULTS:

Molecular Docking Study^{39, 40}:

Table I: Binding energy of ligands with protein crystal structure (PDB Code: 4h1j)

 

 

Fig. 2 Pose view image and PDB–ligand 3D co-crystal structure (Code: 4h1j) showing interactions of ligand 5c

 

 

Fig. 3 Pose view image and PDB–ligand 3D co-crystal structure (Code: 4h1j) showing interactions of ligand 9b

 

Fig. 4 Pose view image and PDB–ligand 3D co-crystal structure (Code: 4h1j) showing interactions of reference ligand

 

Compound 5a: IR: 3041,3335, 2867,1675,1630, 1588,1453; MS (m/z): [M]⁺380.11, [M+1]⁺381.11; Fragments: 231.09, 149.02, 189.08, 191.03, 285.04;
¹H NMR: 7.48-8.03 (4H, m, benzothiazole), 3.78 (1H, t, N-H), 3.11 (2H, d, -CH₂-), 5.51-6.17 (2H, m, pyridazine), 2.28 (6H, s, methyl), 6.24(1H, s, Pyrazole); Elem. Anal. for C₁₈H₁₆N₆O₂S: C, 56.79; H, 4.22; N, 22.10; S, 8.44.

 

Compound 5b: IR: 3324, 3015, 2874, 1677, 1632, 1577, 1468, 1115; MS: [M]⁺410.12, [M+1]⁺ 411.12; Fragments:231.09, 179.03, 315.06, 136.03, 189.08, 221.04;¹H NMR: 7.11-8.01 (3H, m, benzothiazole), 3.26 (1H, s, -Methoxy), 3.41 (1H, t, N-H), 3.76 (2H, d, -CH₂-), 5.61-6.24 (2H, m, pyridazine), 2.19 (6H, s, methyl), 6.04(1H, s, Pyrazole); Elem. Anal. for C₁₉H₁₈N₆O₃S: C, 55.62; H, 4.42; N, 20.44; S, 7.80.

 

Compound 5c: IR: 3042, 3329, 2876, 1678, 1632, 1547, 1485, 1118; MS: [M]⁺380.11, [M+1]⁺381.11; Fragments:231.09, 189.08, 235.05, 193.08, 178.08;¹H NMR: 7.07-7.69 (3H, m, benzothiazole), 3.66 (1H, q, -OCH₂), 1.26 (1H, t, -O-C-CH₃), 3.87 (1H, t, N-H), 3.49 (2H, d, -CH₂-), 6.51-6.77 (2H, m, pyridazine), 2.36 (6H, s, methyl), 6.09 (1H, s, Pyrazole); Elem. Anal. for C₂₀H₂₀N₆O₃S: C, 56.60; H, 4.74; N, 19.79; S, 7.54.

 

Compound 9a: IR:3045, 2873, 1678, 1670, 1587, 1472; MS:[M]⁺380.11, [M+1]⁺381.11; Fragments:231.09, 149.02, 189.08, 285.04, 246.10, 134.01; ¹H NMR: 7.71-8.16 (4H, m, benzothiazole), 6.19 (1H, s, N-H), 3.54 (2H, s, -CH₂-), 5.43-6.10 (2H, m, pyridazine), 2.58 (6H, s, methyl), 6.11 (1H, s, Pyrazole); Elem. Anal. for C₁₈H₁₆N₆O₂S: C, 56.85; H, 4.25; N, 22.08; S, 8.42.

 

Compound 9b: IR: 3037, 2894, 1682, 1679, 1577, 1437, 1116; MS: [M]⁺410.12, [M+1]⁺ 411.12; Fragments: 231.09, 246.10, 179.03, 315.06, 164.02, 189.08; ¹H NMR: 7.45-8.12 (3H, m, benzothiazole), 3.51 (1H, s, -OCH₃), 7.14 (1H, s, N-H), 3.28 (2H, s, -CH₂-), 5.79-6.31 (2H, m, pyridazine), 2.52 (6H, s, methyl), 6.39 (1H, s, Pyrazole); Elem. Anal. for C₁₉H₁₈N₆O₃S: C, 55.62; H, 4.42; N, 20.44; S, 7.80.

 

Compound 9c: IR: 3071, 2891, 1680, 1672, 1588, 1469, 1118; MS: [M]⁺380.11, [M+1]⁺381.11; Fragments: 231.09, 193.04, 136.03, 246.10, 178.03, 329.07;¹H NMR: 7.18-8.05 (3H, m, benzothiazole), 3.76 (1H, q, -OCH₂), 1.28 (1H, t, -O-C-CH₃), 7.59 (1H, s, N-H), 3.32 (2H, s, -CH₂-), 7.06-7.52 (2H, m, pyridazine), 2.71 (6H, s, methyl), 6.29 (1H, s, Pyrazole); Elem. Anal. for C₂₀H₂₀N₆O₃S:C, 56.60; H, 4.75; N, 19.79; S, 7.54.

 

Compound 10a: IR: 3067, 3018, 2869, 1689, 1675, 1632, 1574, 1476, 678; MS: [M]⁺440.01, [M+1]⁺442.01; Fragments: 250.93, 189.08, 222.94, 217.07, 361.09; ¹H NMR: 6.57-7.25 (4H, m, coumarin), 6.26-7.02 (2H, m, pyridazine), 2.64 (6H, s, methyl), 6.17 (1H, s, Pyrazole); Elem. Anal. for C₁₉H₁₃BrN₄O₄: C, 51.74; H, 2.97; Br, 18.10; N, 12.69.

 

Compound10b: IR: 3059, 3042, 1691, 1674, 1633, 712; MS: [M]⁺519.92, [M+1]⁺ 521.92;Fragments: 189.08, 328.84, 439.01, 300.85, 249.23; ¹H NMR: 7.21-8.07 (3H, m, coumarin), 6.74-7.25 (2H, m, pyridazine), 2.73 (6H, s, methyl), 6.43 (1H, s, Pyrazole); Elem. Anal. for C₁₉H₁₂Br₂N₄O₄: C, 43.85; H, 2.33; Br, 30.71; N, 10.76.

 

Compound 10c: IR: 3068, 3039, 2886, 1690, 1674, 1627, 1569, 1455; MS: [M]⁺406.13, [M+1]⁺407.13; Fragments: 189.08, 217.05, 311.07, 361.09; ¹H NMR: 6.87-8.12 (4H, m, coumarin), 3.82 (1H, q, -OCH₂), 1.38 (1H, t, -O-C-CH₃), 6.51-7.06 (2H, m, pyridazine), 2.70 (6H, s, methyl), 6.34 (1H, s, Pyrazole); Elem. Anal. for C₂₁H₁₈N₄O₅: C, 62.08; H, 4.45; N, 13.79.

 

Compound 11a: IR: 3077, 3071, 2904, 1694, 1669, 1544, 1499; MS: [M]⁺362.14, [M+1]⁺ 363.14; Fragments: 189.08, 173.06, 267.08; ¹H NMR: 6.87-7.02 (3H, m, coumarin), 2.43 (3H, s, methyl), 2.95 (2H, s, -CH₂-), 5.84-6.24 (2H, m, pyridazine), 2.49 (6H, s, methyl), 6.61 (1H, s, Pyrazole); Elem. Anal. for C₂₀H₁₈N₄O₃: C, 66.32; H, 5.02; N, 15.45; O, 13.22.

 

Compound 11b: IR: 3064, 3044, 2902, 1689, 1676, 1566, 1479; MS: [M]⁺362.14, [M+1]⁺ 363.14; Fragments: 189.08, 173.06, 267.08; ¹H NMR: 6.96-7.17 (3H, m, coumarin), 2.22 (3H, s, methyl), 3.16 (2H, s, -CH₂-), 5.62-6.21 (2H, m, pyridazine), 2.69 (6H, s, methyl), 6.81 (1H, s, Pyrazole); Elem. Anal. for C₂₀H₁₈N₄O₃: C, 66.30; H, 5.01; N, 15.45; O, 13.24.

 

Compound 11c:IR: 3075, 3062, 2931, 1692, 1679, 1584, 1473; MS: [M]⁺393.11, [M+1]⁺ 394.11; Fragments: 189.08, 204.03, 298.05; ¹H NMR: 7.56-7.98 (3H, m, coumarin), 2.97 (2H, s, -CH₂-), 5.58-6.34 (2H, m, pyridazine), 2.61 (6H, s, methyl), 6.57 (1H, s, Pyrazole); Elem. Anal. for C₁₉H₁₅N₅O₅: C, 58.03; H, 3.85; N, 17.19; O, 20.33.

 

Table II: Antioxidant activity by DPPH, H₂O₂ Scavenging and FRAP method³⁵

Compound Code	IC50		FRAP Value (µM)
	DPPH Scavenging (µM)	H2O2 Scavenging (µM)
5a	208.14	165.43	0.981
5b	189.57	218.13	0.895
5c	98.43	158.16	0.983
9a	382.98	325.46	0.778
9b	127.84	164.71	1.246
9c	283.72	209.47	0.879
10a	288.12	402.42	0.725
10b	243.16	359.48	0.675
10c	152.86	234.26	1.143
11a	268.64	119.28	0.894
11b	315.48	262.83	0.684
11c	264.93	248.91	0.792
AA	68.47	89.75	2.000
BHT	124.67	176.18	1.102

AA: Ascorbic Acid, BHT: Butylated Hydroxy Toluene

 

DISCUSSION:

Molecular docking study of synthesized compounds with oxido-reductase enzyme (PDB Code 4h1j) using Autodock Vina docker in order to determine probable binding ligand for active site. The site for interaction with ligand molecule was identified to define docking cavity. Results of docking study showed there is hydrogen bonding of oxo group of connecting moiety between pyridazinone and benzothiazole with Asp567A (additional hydrogen bonding of oxo group of pyridazinone moiety with Lys457A and Glu474A results into more binding affinity of compound 5c as compared other synthesized compounds). Hydrophobic interactions of pyrazolopyridazinone (Leu556A and Phe568A), benzothiazole (Asp567A, Met478A and His547A) moiety and π- interaction of pyridazinone and pyrazole ring with phe568A residue. The molecules were ranked according to their docking score based on negative lowest binding energy. The first lowest binding energy poses are selected for analysis of docking results and analyzed for various intermolecular interactions. Compounds 5c (binding energy-9.442kCal/mole) and 9b (binding energy-9.144kCal/mole) showed better antioxidant potential as compared to other derivatives, as they are from same series. The predicted minimum binding energies in docking study and experimental results of antioxidant activity showed co-relation. This co-relation of docking study and activity results indicated suitability of selection of target PDB and antioxidant activity method.

 

The structural elucidation was by using FTIR, NMR and MS spectral data. The IR spectra showed peaks at 3335 cm^-1 for NH (2° amine) for confirmation of N-H linkage between benzothiazole and pyridazine. The synthesized compounds showed [M]⁺and[M+1]⁺ peaks in mass spectra along with characteristic base peak and other fragments. ¹H NMR spectra showed multiplet at 5.51-6.17 ppm assigned to aromatic 2H of pyridazine, triplet at 3.78 ppm and singlet at 7.59 ppm for N-H bridge between benzothiazole and pyridazinone and other characteristic peaks confirms structures of synthesized compounds.

 

The results of antioxidant values of the novel title compounds expressed as IC₅₀ in μM against DPPH free radical and H₂O₂ and FRAP value in FRAP method, are shown in table II. Results of antioxidant evaluation using DPPH Scavenging method, 5c and 9b showed IC₅₀ at 98.43μM and 127.84 respectively and compared with AA (68.47μM) and BHT (124.67μM). However, using H₂O₂ Scavenging method, 5c and 11a showed IC₅₀at 158.16μM and 119.28μM respectively and compared with AA (89.75μM) and BHT (176.18μM). Results of antioxidant activity by FRAP method, 9b and 10c showed FRAP value 1.246μM and 1.143μM respectively and compared with AA (2.000μM) and BHT (1.102μM). The results revealed that, binding interaction observed in docking study may be the reason for the better antioxidant potential of synthesized derivatives.

 

CONCLUSION:

The Benzothiazole and Coumarin based 6-(3, 5-dimethylpyrazol-1-yl) pyridazin-3-one Derivatives studied in this work displayed remarkable antioxidant activity. Compounds 5c and 9b have been determined as good antioxidants whereas other compounds in the series showed moderate to less antioxidant activity. The antioxidant profiles of tested compounds provide further scope for their screening for antimicrobial, anti-inflammatory, anticancer and antidepressant activity.

ACKNOWLEDGEMENTS:

Authors are thankful to Central Instrumentation Facility, Savitribai Phule Pune University for providing the spectral data of the synthesized compounds. The authors are also grateful to MAEER’s Maharashtra Institute of Pharmacy and School of Pharmacy, MIT World Peace University, Pune for providing necessary facilities to carry out research work.

 

CONFLICT OF INTEREST:

The authors do not have any conflict of interest regarding publication of their article.

 

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Received on 11.07.2019           Modified on 09.12.2019

Accepted on 17.03.2020         © RJPT All right reserved