Synthesis, anti-inflammatory and analgesic activity of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives

R.D. Hunashal; P.M. Ronad; V.S. Maddi; D. Satyanarayana; M.A. Kamadod

doi:10.1016/j.arabjc.2011.01.003

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Original article

7 (

); 1070-1078

doi:

10.1016/j.arabjc.2011.01.003

Synthesis, anti-inflammatory and analgesic activity of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives

R.D. Hunashal^a,*, P.M. Ronad^b, V.S. Maddi^b, D. Satyanarayana^c, M.A. Kamadod^a

a Department of Pharmacology, Karnataka Institute of Medical Sciences, Hubli 580 021, Karnataka, India

b Department of Pharmaceutical Chemistry, K.L.E.S’s College of Pharmacy, Hubli 580 031, Karnataka, India

c Department of Pharmaceutical Chemistry, NGSM Institute of Pharmaceutical Sciences, Paneer, Deralakatte, Mangalore 574 160, Karnataka, India

*Corresponding author. Tel.: +91 836 2278097; fax: +91 0836 2373724 rajeshrd3@rediffmail.com (R.D. Hunashal)

Received: 2010-11-26, Accepted: 2011-1-4, Published: 2011-12-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Available online 8 January 2011

Peer review under responsibility of King Saud University.

Abstract

The title compounds 3a–l have been synthesized by the reaction of thiocarbohydrazide with substituted phenoxy acetic acid to obtained substituted 1,2,4-triazoles (1). Compound 1 was treated with various substituted aromatic aldehydes which results in 4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-2H-1,2,4-triazol-3(4H)-thiones (2a–g), further 2a–g is converted to 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3a–l) derivatives by the reaction with chloroacetic acid. All the newly synthesized compounds were evaluated for in vivo anti-inflammatory and analgesic activities. Among the series 2-[4-(2,4-dichlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3d), 2-[4-(4-dichlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3e), 2-[4-(2,4-dichlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-4H-1,2,4-triazol-3-yl thio] acetic acid (3j) and 2-[5-[(2,4-dichlorophenoxy)methyl)]-4-(4-chlorobenzylideneamino)-4H-1,2,4-triazol-3-yl thio] acetic acid (3k) showed significant anti-inflammatory activity with P < 0.001 (63.4%, 62.0%, 64.1% and 62.5% edema inhibition, respectively), as compared to the standard drug diclofenac (67.0%) after third hour respectively and also compounds 3j, 3k exhibited significant analgesic activity with P < 0.001 (55.9% and 54.9% protection, respectively) and less ulcerogenic activity as compared with standard drug aspirin (57.8%).

Keywords

1,2,4-Triazole

Schiff Base

1,2,4-Triazolyl thioacetic acid

Anti-inflammatory activity

Analgesic activity

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1 Introduction

Inflammation is a defensive but exaggerated local tissue reaction in response to exogenous or endogenous insult. Cyclooxygenase (COX) and 5-lipoxygenase (5-LO) are enzymes which catalyze the rate-limiting steps in the biosynthesis of prostaglandins and leukotrienes from arachidonic acid. A large number of non-steroidal anti-inflammatory drugs (NSAIDs) are available clinically to treat inflammatory disorders. The most important mechanism of anti-inflammatory action of NSAIDs is considered to be primarily by inhibition of prostaglandin synthesis. The principal side effects associated with chronic use of non selective NSAIDs are gastrointestinal irritation, bleeding and formation of life threatening gastrointestinal ulcer. In addition, there is evidence to suggest that leukotriene promotes gastric ulceration, which limits the therapeutic utilization of these drugs (Lombardino, 1985; Mullican et al., 1993; Osiri and Moreland, 1999 ). Therefore, there is a need to develop new compounds. Literature survey revealed that Schiff bases of 1,2,4-triazoles bearing aryl groups or heterocyclic residues (Olcay et al., 2006) which possess excellent biological activities, viz. antibacterial (Francis et al., 2008), antifungal (Desai et al., 1984), antitubercular (Iraj et al., 2008; Kucukguzel et al., 2008), anticancer (Mahendra et al., 2007; Upadhaya et al., 2004), anti-inflammatory (Fahmy and Soliman, 2001; Latifeh et al., 2006; Yasemin et al., 2007 ) and anticonvulsant activities (Almarirad, 2004).

In view of these facts and in continuation of our research program on synthesis and pharmacological importance of various heterocyclic Schiff bases (Ronad et al., 2008a, 2008b; Maddi et al., 1992; Hunashal et al., 2010 ), now we are reporting the synthesis, anti-inflammatory and analgesic activity of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives. Compounds which showed significant activity in acute anti-inflammatory model were further screened for analgesic and ulcerogenic activity.

2 Experimental

2.1

2.1 General considerations

All research chemicals were purchased from Acros organics (NY, USA), Sigma–Aldrich (St. Loius, Missouri, USA), Lancaster Co. (Ward Hill, MA, USA) and used as such for the reactions. Solvents except laboratory reagent grade were dried and purified according to the literature whenever necessary. Purification of title compounds were carried out by flash chromatography from Biotage Isolera ST-1 (Darmstadt, Germany). Reactions were monitored by thin layer chromatography (TLC) on pre-coated silica gel plates from E. Merck and Co. (Darmstadt, Germany).

Melting points of synthesized compounds were determined in Thermonik melting point apparatus (Chennai, India) and are uncorrected. The IR spectra were recorded on Thermo Nicolet FTIR-200 Spectrometer (Madison, WI, USA), using KBr pellets. The ¹H NMR and ¹³C NMR were recorded on Bruker AVANCE II 400 (Bruker, Rheinstetten/Karlsruhe, Germany) in CDCl₃/DMSO-d₆ as solvent. Chemical shifts are reported in δ ppm units with respect to TMS. The mass spectra were recorded using GCMS-QP 2010 (Shimaduzu, Japan). The anti-inflammatory activity was carried out using digital plethysmometer (Ugo-Basile, Italy). All the animal experiments were approved by Institutional Animal Ethical Committee (IAEC).

2.2

2.2 Synthesis

2.2.1

2.2.1 General method for synthesis of 3-(substituted phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1)

An intimate mixture of thiocarbohydrazide (1.06 g, 0.01 mol) and substituted phenoxy acetic acid (0.01 mol) was heated in an oil bath at 175–180 °C for 2 h. The fused mass was triturated with hot water, filtered and washed with sodium bicarbonate. The crude product was recrystallized from methanol.

2.2.1.1

2.2.1.1 3-(Phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1a)

C₉H₁₀N₄OS, mp 186–187 °C, Yield is 69.0%.

IR (KBr, cm⁻¹): 3215.4 (NH₂), 3209.4 (NH), 2363.2 (SH), 1628.3, 1589.2 (C⚌N).

¹H NMR (DMSO-d₆, δ ppm): 13.6 (br, 1H, SH), 7.6–6.9 (m, 5H, Ar-H), 5.1 (s, 2H, OCH₂) and 3.3 (s, 2H, NH₂).

MS (ESI) (M⁺): m/z 222.0; calcd. 222.2.

2.2.1.2

2.2.1.2 3-(2,4-Dichloro phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1b)

The compound was further purified by flash chromatography using dimethyl formamide (DMF) and methanol as mobile phase.

C₉H₈Cl₂N₄OS, mp 130–132 °C, Yield is 62.6%.

IR (KBr, cm⁻¹): 3457.4 (NH₂), 3241.1 (NH), 1620.6 (C⚌N), 1282.1 (C⚌S), 781.5 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆ δppm): 7.8–6.8 (m, 3H, Ar-H and NH), 4.5 (s, 2H, OCH₂), 2.1 (s, 2H, NH₂).

2.2.2

2.2.2 General method for synthesis of 4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-2H-1,2,4-triazole-3(4H)-thione (2a–g)

A mixture of N′-4-amino-5-(substituted phenoxymethyl)-2H-1,2,4-triazole-3(4H)-thione (1) (0.01 mol) and the corresponding various aromatic aldehydes (0.01 mol) in ethanol (25 ml) was treated with concentrated HCl (0.5 ml) and refluxed for 2 h. The reaction mixture was cooled to room temperature and the separated crystalline compound is filtered and recrystallized from ethanol to give 2a–g.

2.2.2.1

2.2.2.1 4-(4-Methylbenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazolo-3-thiol (2a)

IR (KBr, cm⁻¹): 3054.3 (Ar-H), 2916.8 (OCH₂), 2755.2 (SH), 1594.0 (HC⚌N), 1534.5 (C⚌N).

¹H NMR (400 MHz, CDCl₃, δ ppm): 10.5 (br, 1H, SH), 10.2 (s, 1H, HC⚌N), 7.2–6.9 (m, 9H, Ar-H), 5.2 (s, 2H, OCH₂), 2.4 (s, 3H, CH₃).

MS (ESI) (M+1): 325.3; calcd. 324.4.

¹³C NMR (400 MHz, CDCl₃, δ ppm): 163.4 (triazole-C₃), 146.7 (triazole-C₅), Ar C [158.9 (C₁), 129.3 (C₃ and C₅), 123.3 (C₆), 122.2 (C₄), 115.3 (C₂)], 155.9 (–CH⚌N), Ar C (benzylidene) [139.8 (C₄), 131.2 (C₃ and C₅), 130.2 (C₂ and C₆), 129.9 (C₁)], 68.9 (OCH₂), 61.2 (OCH₃), 24.5 (CH₃).

2.2.2.2

2.2.2.2 4-(4-Nitrobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2b)

IR (KBr, cm⁻¹): 3050.4 (Ar C–H), 2461.2 (SH), 1592.3 (HC⚌N), 1545.7 (NO₂), 1531.3 (C⚌N), 1285.7 (C⚌S), 825.3 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 12.8 (s, 1H, SH), 8.9 (s, 1H, HC⚌N), 7.4–6.8 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 152.8 (triazole-C₃), 176.9 (triazole-C₅), Ar C [152.1 (C₁), 130.3 (C₅), 128.3 (C₃ and C₄), 124.2 (C₆), 116.3 (C₂)], 142.3 (HC⚌N), Ar C (benzylidene) [139.6 (C₁), 138.6 (C₂ and C₄), 127.6 (C₆), 120.6 (C₃ and C₅)], 64.8 (OCH₂).

MS (ESI): m/z 424.2; calcd. 424.0.

2.2.2.3

2.2.2.3 4-(4-Methoxyoxybenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2c)

IR (KBr, cm⁻¹): 3061.1 (Ar C–H), 2924.3 (OCH₂), 2547.2 (SH), 1606.5 (HC⚌N), 1537.3 (C⚌N), 824.5 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.6 (s, 1H, SH), 8.1 (s, 1H, N⚌CH), 7.7–6.9 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 3.3 (s, 3H, OCH₃).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 154.8 (triazole-C₃), 182.8 (triazole-C₅), Ar C [153.1 (C₁), 131.8 (C₅), 128.7 (C₃ and C₄), 123.3 (C₆), 116.9 (C₂)], 142.9 (HC⚌N), Ar C (benzylidene) [161.7 (C₄), 130.5 (C₂ and C₆), 125.3 (C₁), 114.7 (C₃ and C₅)], 68.9 (OCH₂), 60.2 (OCH₃).

2.2.2.4

2.2.2.4 4-(2-Hydroxybenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2d)

IR (KBr, cm⁻¹): 3093.8 (OH), 3063.3 (Ar C–H), 2926.3 (OCH₂), 2547.8 (SH), 1596.3 (HC⚌N), 1532.5 (C⚌N), 826.2 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.6 (br, 1H, SH), 10.2 (s, 1H, HC⚌N), 8.3 (s,1H, OH), 7.3–6.9 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂).

MS (ESI) (M+1): 396.2; calcd. 395.2.

2.2.2.5

2.2.2.5 4-(2,4-Dichlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2e)

IR (KBr, cm⁻¹): 3055.5 (Ar C–H), 2925.4 (OCH₂), 2554.2 (SH), 1610.4 (HC⚌N), 1532.7 (C⚌N), 834.2 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.3 (s, 1H, SH), 8.4 (s, 1H, HC⚌N), 7.3–6.9 (m, 6H, Ar-H), 5.2 (s, 2H, OCH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 154.4 (triazole-C₃), 180.7 (triazole-C₅), Ar C [152.4 (C₁), 131.3 (C₅), 128.2 (C₃ and C₄), 124.7 (C₆), 116.8 (C₂)], 142.7 (HC⚌N), Ar C (benzylidene) [129.6 (C₁), 136.4 (C₂ and C₄), 133.0 (C₆), 128.6 (C₃ and C₅)], 68.9 (OCH₂).

MS (ESI): m/z 448.1; calcd. 448.0.

2.2.2.6

2.2.2.6 4-(4-Chlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2f)

IR (KBr, cm⁻¹): 3039.2 (Ar C–H), 2916.4 (OCH₂), 2543.6 (SH), 1608.7 (HC⚌N), 1533.8 (C⚌N), 826.7 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 10.9 (s, 1H, SH), 8.2 (s, 1H, HC⚌N), 7.3–6.9 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂).

MS (ESI) (M+1): m/z 413.7; calcd. 412.0.

2.2.2.7

2.2.2.7 4-(4-Methylbenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2g)

IR (KBr, cm⁻¹): 3039.8 (Ar-H), 2927.4 (OCH₂), 2564.6 (SH), 1604.5 (C⚌N), 825.3 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.3 (br, 1H, SH), 9.2 (s, 1H, HC⚌N), 7.3–6.8 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 2.5 (s, 3H, CH₃).

2.2.3

2.2.3 General method for synthesis of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3a–l)

Equimolar proportions of 2a–g and chloroacetic acid were dissolved in ethanol containing 3–4 drops of pyridine and refluxed for 2–3 h, on pouring the reaction mixture into cold water a solid 3a–l was separated which was filtered, washed with water and recrystallized from ethanol to give 3a–l.

2.2.3.1

2.2.3.1 2-[4-(4-Nitrobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3a)

IR (KBr, cm⁻¹): 3200.0 (OH), 3068.9 (Ar C–H), 2928.4 (OCH₂), 2374.2 (CH₂), 1715.6 (C⚌O), 1590.1 (C⚌N), 1580.4 (NO₂).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 13.8 (s, 1H, OH), 10.8 (s, 1H, HC⚌N), 8.2–6.9 (m, 9H, Ar-H), 5.1 (s, 2H, OCH₂), 1.1 (s, 2H, CH₂).

¹³C NMR (400 MHz, CDCl₃, δ ppm): 178.0 (C⚌O), 162.8 (triazole-C₃), 157.9 (triazole-C₅), Ar C [156.1 (C₁), 129.3 (C₃ and C₅), 124.0 (C₄ and C₆), 115.1 (C₂)], 162.8 (HC⚌N), Ar C (benzylidene) [149.6 (C₁), 138.6 (C₄), 129.6 (C₃ and C₅), 127.6 (C₂ and C₆)], 59.8 (OCH₂), 29.5 (S–CH₂).

MS (ESI): m/z 413.3; calcd. 413.4.

2.2.3.2

2.2.3.2 2-[4-(4-Methoxybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3b)

IR (KBr, cm⁻¹): 3117.6 (OH), 3056.3 (Ar C–H), 2952.6 (OCH₂), 2755.3 (CH₂), 1733.4 (C⚌O), 1598.5 (C⚌N).

¹H NMR (400 MHz, CDCl₃, δ ppm): 13.7 (s, 1H, OH), 10.0 (s, 1H, N⚌CH), 7.7–6.8 (m, 9H, Ar-H), 5.2 (s, 2H, OCH₂), 3.7 (s, 3H, OCH₃), 1.1 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 169.3 (C⚌O), 162.0 (triazole-C₃), 146.6 (triazole-C₅), Ar C [157.3 (C₁), 129.1 (C₃ and C₅), 114.6 (C₄), 113.9 (C₂ and C₆)], 162.6 (–CH⚌N), Ar C (benzylidene) [130.6 (C₄), 130.1 (C₁), 124.4 (C₂ and C₆), 121.3 (C₃ and C₅)], 59.3 (OCH₂), 55.0 (OCH₃), 38.9 (S–CH₂).

2.2.3.3

2.2.3.3 2-[4-(4-Methylybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3c)

IR (KBr, cm⁻¹): 3200.2 (OH), 3055.2 (Ar-H), 2916.5 (OCH₂), 2755.2 (CH₂), 1734.0 (C⚌O), 1594.7 (C⚌N).

¹H NMR (400 MHz, CDCl₃, δ ppm): 13.5 (br, 2H, 2-OH), 10.2 (br, 1H, HC⚌N), 7.5–6.8 (m, 9H, Ar-H), 5.1 (s, 2H, OCH₂), 1.2 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 169.3 (C⚌O), 157.3 (triazole-C₃), 136.9 (triazole-C₅), Ar C [134.4 (C₁), 129.6 (C₃ and C₅), 115.9 (C₂ and C₆), 117.3 (C₄)], 157.3 (HC⚌N), Ar C (benzylidene) [159.4 (C₂), 132.1 (C₅), 122.0 (C₁ and C₃), 119.9 (C₄ and C₆)], 59.9 (OCH₂), 39.4 (S–CH₂).

MS (ESI) (M−2): m/z 382.4; calcd. 384.4.

2.2.3.4

2.2.3.4 2-[4-(2,4-Dichlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3d)

IR (KBr, cm⁻¹): 3200.0 (OH), 3051.3 (Ar C–H), 2920.4 (OCH₂), 2373.5 (CH₂), 1735.1 (C⚌O), 1589.5 (C⚌N).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 13.9 (s, 1H, OH), 11.0 (s, 1H, HC⚌N), 7.9–6.9 (m, 9H, Ar-H), 5.2 (s, 2H, OCH₂), 1.2 (s, 2H, CH₂).

2.2.3.5

2.2.3.5 2-[4-(4-Chlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3e)

IR (KBr, cm⁻¹): 3200.2 (OH), 3050.5 (Ar C–H), 2914.8 (OCH₂), 2373.8 (CH₂), 1716.4 (C⚌O), 1591.0 (C⚌N).

¹H NMR (400 MHz, CDCl₃, δ ppm): 13.8 (s, 1H, OH), 10.5 (s, 1H, HC⚌N), 7.7–6.9 (m, 9H, Ar-H), 5.2 (s, 2H, OCH₂), 2.5 (br, 2H, CH₂).

2.2.3.6

2.2.3.6 2-[4-(2-Hydroxybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3f)

IR (KBr, cm⁻¹): 3098.8 (OH), 3051.2 (Ar C–H), 2915.9 (OCH₂), 2751.6 (CH₂), 1734.9 (C⚌O), 1595.4 (C⚌N).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 13.7 (s, 1H, OH), 10.1 (s, 1H, HC⚌N), 7.6–6.8 (m, 9H, Ar-H), 5.1 (s, 2H, OCH₂), 2.3 (s, 3H, CH₃), 1.1 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 162.5 (C⚌O), 162.5 (triazole-C₃), 143.1 (triazole-C₅), Ar C [157.9 (C₁), 129.6 (C₃ and C₅), 121.8 (C₄), 115.1 (C₂ and C₆)], 147.2 (–CH⚌N), Ar C (benzylidene) [129.7 (C₄), 129.5 (C₂ and C₆), 129.1 (C₁), 128.7 (C₃ and C₅)], 59.8 (OCH₂), 39.4 (S–CH₂), 21.7 (CH₃).

MS (ESI) (M−1): m/z 381.4; calcd. 382.4.

2.2.3.7

2.2.3.7 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-nitrobenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3g)

IR (KBr, cm⁻¹): 3210.2 (OH), 3060.4 (Ar C–H), 2920.7 (OCH₂), 2360.3 (CH₂), 1710.6 (C⚌O), 1600.3 (C⚌N), 1545.8 (NO₂), 768.7 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 12.1 (br, 1H, OH), 10.2 (s, 1H, HC⚌N), 8.2–6.5 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 2.1 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 173.6 (C⚌O), 162.8 (triazole-C₃), 146.5 (triazole-C₅), Ar C [152.3 (C₁), 131.8 (C₂), 130.6 (C₃), 128.3 (C₄ and C₅), 117.4 (C₆)], 157.8 (HC⚌N), Ar C (benzylidene) [149.8 (C₄), 139.6 (C₁), 129.4 (C₂ and C₆), 127.6 (C₃ and C₅)], 62.3 (OCH₂), 33.7 (S–CH₂).

MS (ESI): m/z 482.2; calcd. 482.4.

2.2.3.8

2.2.3.8 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-methoxybenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3h)

IR (KBr, cm⁻¹): 3200.2 (OH), 3060.2 (Ar C–H), 2915.6 (OCH₂), 2350.2 (CH₂), 1725.6 (C⚌O), 1610.3 (C⚌N), 872.4 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.2 (s, 1H, OH), 10.1 (s, 1H, HC⚌N), 7.5–6.6 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 3.7 (s, 3H, OCH₃), 2.5 (s, 2H, CH₂).

MS (ESI): m/z 467.2 calcd. 467.3

2.2.3.9

2.2.3.9 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(2-hydroxybenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3i)

IR (KBr, cm⁻¹): 3208.6 (OH), 3057.0 (Ar C–H), 2903.4 (OCH₂), 2350.7 (CH₂), 1720.3 (C⚌O), 1610.3 (C⚌N), 872.4 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.9 (s, 2H, OH), 10.4 (s, 1H, N⚌CH), 7.2–6.6 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 2.8 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 173.8 (C⚌O), 162.7 (triazole-C₃), 147.3 (triazole-C₅), Ar C [152.7 (C₁), 131.3 (C₂), 130.5 (C₃), 128.1 (C₄ and C₅), 116.9 (C₆)], 156.9 (HC⚌N), Ar C (benzylidene) [159.8 (C₂), 132.8 (C₄), 130.2 (C₆), 118.6 (C₁), 117.3 (C₃ and C₅)], 62.9 (OCH₂), 34.6 (S–CH₂).

MS (ESI) (M−1): m/z 452.3; calcd. 453.3.

2.2.3.10

2.2.3.10 2-{4-(2,4-Dichlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-4H-1,2,4-triazol-3-yl thio} acetic acid (3j)

IR (KBr, cm⁻¹): 3110.4 (OH), 3065.6 (Ar C–H), 2930.3 (OCH₂), 2363.6 (CH₂), 1720.3 (C⚌O), 1610.5 (C⚌N), 795.3 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 13.1 (s, 1H, OH), 10.3 (s, 1H, N⚌CH), 7.2–6.5 (m, 6H, Ar-H), 5.2 (s, 2H, OCH₂), 2.7 (s, 2H, CH₂).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 173.0 (C⚌O), 162.5 (triazole-C₃), 146.6 (triazole-C₅), Ar C [151.9 (C₁), 131.4 (C₂), 131.7 (C₃), 127.9 (C₄ and C₅), 117.9 (C₆)], 158.2 (HC⚌N), Ar C (benzylidene) [139.3 (C₄), 136.42(C₂), 132.2 (C₆), 131.3 (C₁), 129.4 (C₃ and C₅)], 60.4 (OCH₂), 34.3 (S–CH₂).

MS (ESI): m/z 506.4; calcd. 506.3.

2.2.3.11

2.2.3.11 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-chlorobenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3k)

IR (KBr, cm⁻¹): 3210.2 (OH), 3060.4 (Ar C–H), 2920.7 (OCH₂), 2360.3 (CH₂), 1712.3 (C⚌O), 1600.3 (C⚌N), 856 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 13.2 (br, 1H, OH), 10.2 (s, 1H, HC⚌N), 7.6–6.5 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 2.8 (s, 2H, CH₂).

MS (ESI) (M+1): m/z 472.8; calcd. 471.7.

2.2.3.12

2.2.3.12 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-methylbenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3l)

IR (KBr, cm⁻¹): 3200.8 (OH), 3063.0 (Ar C–H), 2914.4 (OCH₂), 2351.3 (CH₂), 1720.3 (C⚌O), 1613.5 (C⚌N), 872.4 (C–Cl).

¹H NMR (400 MHz, DMSO-d₆, δ ppm): 11.7 (s, 1H, OH), 10.4 (s, 1H, N⚌CH), 7.5–6.6 (m, 7H, Ar-H), 5.2 (s, 2H, OCH₂), 2.9 (s, 2H, CH₂), 2.3 (s, 3H, CH₃).

¹³C NMR (400 MHz, DMSO-d₆, δ ppm): 172.8 (C⚌O), 162.7 (triazole-C₃), 147.3 (triazole-C₅), Ar C [152.2 (C₁), 123.8 (C₂), 131.0 (C₃), 129.0 (C₄ and C₅), 117.2 (C₆)], 157.5 (HC⚌N), Ar C (benzylidene) [139.9 (C₄), 130.2 (C₂ and C₆), 129.5 (C₁), 117.3 (C₃ and C₅)], 62.3 (OCH₂), 34.8 (S–CH₂), 24.4 (CH₃).

MS (ESI) (M+1): m/z 452.3; calcd. 451.3.

3 Pharmacological screening

3.1

3.1 Animals

Albino mice of either sex weighing between 20 and 25 g were used for acute toxicity and analgesic activity studies. Healthy male albino adult rats weighing between 150 and 230 g were used for anti-inflammatory and ulcerogenic activities. Animal ethical clearance was obtained from Ethics Committee of K.S. Hegde Medical Academy, Deralakatte, Mangalore, India (115/1999/CPCSEA). Animals were procured from K.S. Hegde Medical Academy, Deralakatte, Mangalore, India, and housed individually in polypropylene cages, maintained under standard conditions of alternating 12-h light-and-dark cycles at a constant temperature (25 ± 2 °C and 35–60% relative humidity). Animals were fed with standard rat pellet diet, (Hindustan Lever Ltd., Mumbai, India) and water ad libitum.

3.2

3.2 Acute toxicity

The acute toxicity test was carried out according to OECD guidelines (OECD, 2000) to establish the effective dose of the test compounds after obtaining ethical clearance from Ethics Committee of K.S. Hegde Medical Academy, Deralakatte, Mangalore, India. Albino mice of either sex weighing between 20 and 25 g were divided into six groups of 6 animals each. Animals were starved for 24 h with water ad libitum prior to test. On the day of the experiment, animals were administered with different compounds to different groups in an increasing dose of 10, 20, 100, 200, 1000 and 2000 mg/kg body weight orally. The animals were then observed continuously for 3 h for general behavioral, neurological, autonomic profiles and then every 30 min for next 3 h and finally for next 24 h or till death.

From preliminary toxicity studies, it was observed that animals were found to be safe up to a maximum dose of 2000 mg/kg body weight. But there were few changes in the behavioral response like alertness, touch response, and restlessness. Therefore, 1/10th of the maximum tolerated dose, i.e. 200 mg/kg body weight (b.w.) was chosen for the studies.

3.3

3.3 In vivo anti-inflammatory activity

In vivo anti-inflammatory activity was evaluated by carrageenan-induced rat paw edema assay model (Winter et al., 1962) for the compounds listed in Table 1. Male albino rats (170–220 g) of either sex were used. The animals were divided randomly into fourteen groups of six each. They were starved overnight with water ad libitum prior to the day of experiment. Control group received 1 ml of 0.5% sodium carboxymethyl cellulose (sodium CMC), standard group received 13.5 mg/kg diclofenac and test groups received 200 mg/kg of synthesized compounds 3a–l orally. One hour later; a sub plantar injection of 0.05 ml of 1% solution of carrageenan (Sigma) in sterile distilled water was administered to the left hind footpad of each animal. The paw edema volume was measured with a digital plethysmometer at 0, 1, 2, 3, 4, 5 and 6 h after carrageenan injection. Paw edema volume was compared with vehicle control group and percent reduction was calculated as $% edema inhibition = 1 - Vt / Vc \times 100$ where, Vt and Vc were edema volume in treated and control groups, respectively.

3.4

3.4 Analgesic activity (Koster et al., 1959)

Twenty-four hours prior to actual testing a large number of albino mice of either sex weighing between 20 and 25 g received intraperitoneally 10 mg/kg 0.6% glacial acetic acid. Animals were observed for writhing movements. Only those showing one or other type of writhing movements (positive responders) were chosen for the test on the next day. On the test day the responders received compounds half an hour prior to glacial acetic acid challenge. Compounds 3d, 3e, 3j and 3k were orally administered at a dose of 200 mg/kg as a suspension in 0.5% sodium CMC. Standard drug used was aspirin at a dose of 30 mg/kg as a suspension in 0.5% sodium CMC. Each mouse was then observed for the total number of stretching episodes or writhings for 15 min following glacial acetic acid injection. The mean value for each group was calculated.

3.5

3.5 Gastric ulceration (Alich et al., 1983)

Rats of either sex were fasted for 24 h. Test compounds and positive control Aspirin were administered at a dose of 250 mg/kg p.o. in a group of six rats. Similarly the negative controls were treated with 10 ml/kg 0.5% sodium CMC. Four hours after treatment, the rats were sacrificed; the stomach was removed, opened along the lesser curvature and observed for gastric lesions on the mucosa. The lesion index for each group was determined according to a previously reported method, by counting the number of lesions (x) in each of five size classes (y). The classes were defined as y = 1 (pinpoint lesion), y = 2 (lesions < 1 mm diameter), y = 3 (lesions 1–2 mm diameter), y = 4 (lesions 2–4 mm diameter) and y = 5 (lesions > 4 mm diameter). The lesions index was calculated using the formula $\sum_{i = 1}^{5} x_{i} y_{i}$ .

3.6

3.6 Statistical analysis

Data were presented as arithmetic mean ± SEM. Statistical analysis was performed by one way variance (ANOVA) followed by Dunnett’s test. “p” value of less than 0.05 was considered as statistically significant using PARAMETRIC STASTICS, IBM PC version 1.01 by Londan soft ware INC-1985.

4 Results and discussion

A novel series of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives (3a–l) were synthesized as shown in Scheme 1 by the reaction between thiocarbohydrazide and substituted phenoxy acetic acid, which on fusion will yield 3-(substituted phenoxymethyl)-4-amino-5-mercapto-1,2,4-triazoles (1). Compound 1 was treated with various substituted aromatic aldehydes in ethanol medium in presence concentrated hydrochloric acid at 90 °C for 2 h. It resulted in 2a–g, which converted to compounds 3a–l by the reaction with chloroacetic acid in absolute ethanol medium in presence of drop of pyridine as catalyst and refluxed for 2–3 h. The purity of the compounds was confirmed by TLC using silica gel G as stationary phase and suitable solvent system as mobile phase and by melting point. Structure of all the newly synthesized compounds is well supported by the spectral data such as IR, ¹H NMR, ¹³C NMR, mass and elemental analysis. The physical data of compounds is tabulated in Table 1.

Synthesis of 2-[4-(substituted bezylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives (3a–l). Reagents and conditions: (a) Heat 175–180 °C, oil bath, 2–3 h. (b) Aromatic aldehydes, absolute ethanol, reflux, 2 h. (c) Chloroacetic acid, ethanol, reflux, 2–3 h.

The IR spectrum of compound 1 showed characteristic absorption bands at 3457.4 cm⁻¹ due to NH₂ and the other at 1282.1/2580 cm⁻¹ was attributed to C⚌S/SH. The ¹H NMR characteristic signal showed at δ 13.2/7.8 as a singlet due to SH/NH proton derived from tautomeric equilibrium of compound 1 and δ 2.1 due to NH₂ protons.

The IR spectrum of compound 2a–g showed a characteristic absorption bands at range of 1588.5–1610.4 cm⁻¹ and 1531.3–1535.7 cm⁻¹ due to the presence of HC⚌N of Schiff base and C⚌N of triazole ring, respectively. The ¹H NMR spectrum of these compounds displayed a singlet at δ 8.1 to δ 10.4 which accounted HC⚌N. The ¹³C NMR data which displayed characteristic signal at δ 142.3 to δ 155.9 due to HC⚌N. It suggests the formation of Schiff base. The structure of compounds was further conformed by evidence for the formation of Schiff base, which was obtained by mass spectral data.

The IR spectrum of compound 3a–l showed characteristic absorption bands at range of 3098.8–3210.2 cm⁻¹ was attributed to OH and 1710.6–1735.1 cm⁻¹ accounting for C⚌O of carboxyl group. The ¹H NMR spectrum of these compounds displayed a broad singlet at δ 13.5 to δ 13.9 due to OH of carboxyl group and singlet at δ 1.1 to δ 2.9 due to S–CH₂ protons indicates the formation of S–CH₂–COOH at 5th position of triazole. The ¹³C NMR data observed characteristic singlet at δ 29.5 to δ 39.4 due to S–CH₂. It reveals the formation of thioacetic acid by the reaction of SH with chloroacetic acid. The structure of compounds was further supported by mass spectral data.

All compounds 3a–l were subjected for preliminary toxicity studies, according to Organization for Economic Co-operation and Development (OECD) guidelines in mice. Compounds were found to be safe up to 2000 mg/kg body weight (b.w.). Therefore 1/10th of the maximum tolerated dose, i.e., 200 mg/kg b.w. was used as therapeutic dose.

Acute anti-inflammatory activity by carrageenan induced rat paw edema model by Winter et al. Diclofenac was used as reference standard. The anti-inflammatory activity results revealed that the compounds 3d, 3e, 3j and 3k exhibited significant anti-inflammatory activity (up to 63.4%, 62.0%, 64.1% and 62.5% edema inhibition, respectively), as compared to the standard drug diclofenac (67.0%) after third hour. Where as compounds 3g–i, 3l showed good anti-inflammatory activity and among compounds 3a–c, 3f showed lesser degree anti-inflammatory activity compared to that of standard drug Diclofenac. The anti-inflammatory activity of these compounds may be attributed to the inhibition of cyclooxygenase enzyme, which plays vital role in the inflammation process. The results indicating the percentage inhibition of inflammation have been shown in Table 2.

Table 2 Anti-inflammatory activity of 2-[4-(substituted bezylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives (3a–l).

Compound	Paw mean volume (±SEM)	Edema inhibition at 3 h (%)
Control	0.443 ± 0.008	–
3a	0.339 ± 0.021	23.5
3b	0.330 ± 0.028	25.5
3c	0.328 ± 0.022	25.9
3d	0.162 ± 0.011^⁎⁎	63.4^⁎⁎
3e	0.168 ± 0.014^⁎⁎	62.0^⁎⁎
3f	0.345 ± 0.023	22.1
3g	0.322 ± 0.020^*	27.3^*
3h	0.322 ± 0.021^*	27.3^*
3i	0.316 ± 0.018^*	28.6^*
3j	0.159 ± 0.013^⁎⁎	64.1^⁎⁎
3k	0.166 ± 0.018^⁎⁎	62.5^⁎⁎
3l	0.320 ± 0.006^*	27.8^*
Diclofenac	0.146 ± 0.017^⁎⁎	67.0^⁎⁎

Dose of 200 mg/kg b.w., p.o.

* p ⩽ 0.05.

⁎⁎ p ⩽ 0.001.

Abdominal construction responses induced by acetic acid is a sensitive procedure to establish efficacy of peripherally-acting analgesics, it may causes increase in the level of PGE₂ and PGF_2α by intraperitoneally administration of acetic acid. The analgesic activity was expressed as percentage of protection. Among the series compounds 3j, 3k showed significant analgesic activity (up to 55.9%, 54.9% protection, respectively), where as among compounds 3d, 3e showed good analgesic activity (up to 53.9%, 53.6% protection, respectively), as compared to the standard drug aspirin (57.8%) as illustrated in Table 3.

Table 3 Analgesic activity of 2-[4-(substituted bezylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives (3a–l).

Compound	No. of wriths in 15 min (mean ± SEM)	(%) Protection
Control	68.6 ± 7.0	–
3d	31.3 ± 3.4	53.9^*
3e	31.8 ± 7.6	53.6^*
3j	30.2 ± 8.3	55.9^⁎⁎
3k	30.9 ± 3.6	54.9^⁎⁎
Aspirin	29.0 ± 5.6	57.8^⁎⁎

Dose of 200 mg/kg b.w., p.o.

* p ⩽ 0.05.

⁎⁎ p ⩽ 0.001.

Among the compounds 3d, 3e, 3j and 3k, the compound 3j showed highest anti-inflammatory and analgesic activities because of two chlorine groups at ortho and para position on both phenoxymethyl ring and imine phenyl ring. Hence, it reveals that the compounds having more than one electron withdrawing group (halogen) on phenoxymethyl ring and imine phenyl ring showed increasing anti-inflammatory and analgesic activities.

The major drawback of non steroidal anti-inflammatory drugs is their gastric side effects. In order to determine the extent of these effects, the compounds 3d, 3e, 3j and 3k were further tested for ulcerogenicity (Rainsford, 1975) in rats at 200 mg/kg. All four compounds showed comparable ulcerogenic activity when compared to standard drug aspirin. Among these 3j, 3k showed less ulcerogenic activity, respectively. Results are shown in Table 4.

Table 4 Ulcerogenic activity of 2-[4-(substituted bezylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives (3a–l).

Compound	Ulcer index ± SEM
Control	1.4 ± 0.45
3d	4.7 ± 1.33^*
3e	4.5 ± 1.26^*
3j	3.9 ± 1.22^*
3k	3.6 ± 1.30^*
Aspirin	5.3 ± 1.55^*

Dose 200 mg/kg p.o.

* p ⩽ 0.05.

5 Conclusion

The present study revealed that the synthesis of the title compounds had satisfactory yields. It was observed that the test compounds 3j and 3k containing electron withdrawing moiety (halogen) on phenyl group of Schiff base as well as on phenoxymethyl were found to have significant anti-inflammatory and analgesic activity compared to the standard. Results of these compounds showed less ulcerogenic activity to aspirin. These can be regarded as strong candidates for future investigations.

Conflict of interest statements

The authors have declared no conflict of interest.

Acknowledgements

The authors are thankful to Dr. B.S. Madakatti, Director, Karnataka Institute of Medical Sciences, Hubli, India and Dr. C.S. Shastri, Principal, NGSM Institute of Pharmaceutical Sciences, Deralakatte, Mangalore, India for providing necessary facilities to carry out this research work. We are grateful to director, SAIF, Punjab University, Chandigarh, India for providing the spectral data. We also wish to thank Dr. Y.S. Agasimundin, Dr. R.H. Udupi, Professor B.C. Revanasiddappa and Smt. Rajani Bagewadi for their support and encouragements.

References

Alich A.A., Welsh V.J., Wittmess L.E., . J. Pharm. Sci.. 1983;72:1457-1461.
Almarirad A., . Bioorg. Med. Chem. Lett.. 2004;14:6057-6059.
Desai N.C., Shukla H.K., Thaker K.A., . J. Indian Chem. Soc.. 1984;61:239-241.
Fahmy H.H., Soliman G.A., . Arch. Pharmacol. Res.. 2001;24(3):180-189.
Francis G., Cedric L., Fabrice P., Damien C., Patrice L., Marc Le B., . Bioorg. Med. Chem. Lett.. 2008;18:1820-1824.
Hunashal R.D., Ronad P.M., Satyanarayana D., Maddi V.S., Kamadod M.A., . Int. J. Drug Des. Drug Disc.. 2010;1:107-114.
Iraj R., Charalabou C., Panagiotis Z., Athina G., Marina S., Jasmina G., . Bioorg. Med. Chem.. 2008;16:1160-1161.
Koster R., Anderson M., Debeer E., . Fed. Proc. Fed. Am. Soc. Exp. Biol.. 1959;18:412-413.
Kucukguzel I., Esra T., Guniz Kucukguzel S., Rollas S., De Clercq E., . Eur. J. Med. Chem.. 2008;43:381-392.
Latifeh N., Hamed S., Khosrou A., Mohsen A., Mohammad H., Ghahremani R., . Bioorg. Med. Chem.. 2006;14:2507-2517.
Lombardino G., . Nonsteroidal Antiinflammatory Drugs. New York: Wiley Interscience, John Wiley and Sons; 1985. pp. 3–15
Maddi V., Raghu K.S., Rao M.N.A., . J. Pharm. Sci.. 1992;81:964-966.
Mahendra R.S., Kiran K.M., Hanimi R.G., Tatikonda S., Chakravarthy A.K., Dolly P., . Bioorg. Med. Chem.. 2007;15:3997-4008.
Mullican M.D., Wilson M.W., Connor D.T., Kostlan C.R., Schrier D.J., Dyer D., . J. Med. Chem.. 1993;36:1902-1909.
OCED/OCDC, OECD, October 2000. Guidelines for testing of chemicals. Revised draft guidelines 423, acute oral toxicity class method, Revised document.
Olcay B., Bahittin K., Murat K., . Turk. J. Chem.. 2006;30:29-40.
Osiri M., Moreland L.W., . Arthitis Care Res.. 1999;12:351-362.
Rainsford K.D., . Gut. 1975;16:514-527.
Ronad P.M., Hunashal R.D., Satyanarayana D., Maddi V.S., . Arzneim. Forsch. (Drug Res.). 2008;58:641-646.
Ronad P.M., Satyanarayana D., Hunashal R.D., Maddi V.S., . Arch. Pharm. Chem. Life Sci.. 2008;341:696-700.
Upadhaya R.S., Sinha N., Jain S., Kishore N., Chandra R., Arora S., . Bioorg. Med. Chem.. 2004;12:2225-2228.
Winter C.A., Risley E.A., Nuss G.W., . Proc. Soc. Exp. Biol. Med.. 1962;111:544-547.
Yasemin D., Bilge C., Esra K., Fethi S., Ningur N., . Turk. J. Chem.. 2007;31:1-13.

Introduction

Experimental

General considerations
Synthesis

Pharmacological screening

Animals
Acute toxicity
In vivo anti-inflammatory activity
Analgesic activity (Koster et al., 1959)
Gastric ulceration (Alich et al., 1983)
Statistical analysis

Results and discussion

Conclusion

Conflict of interest statements

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[1] Alich A.A., Welsh V.J., Wittmess L.E., . J. Pharm. Sci.. 1983;72:1457-1461.

[2] Almarirad A., . Bioorg. Med. Chem. Lett.. 2004;14:6057-6059.

[3] Desai N.C., Shukla H.K., Thaker K.A., . J. Indian Chem. Soc.. 1984;61:239-241.

[4] Fahmy H.H., Soliman G.A., . Arch. Pharmacol. Res.. 2001;24(3):180-189.

[5] Francis G., Cedric L., Fabrice P., Damien C., Patrice L., Marc Le B., . Bioorg. Med. Chem. Lett.. 2008;18:1820-1824.

[6] Hunashal R.D., Ronad P.M., Satyanarayana D., Maddi V.S., Kamadod M.A., . Int. J. Drug Des. Drug Disc.. 2010;1:107-114.

[7] Iraj R., Charalabou C., Panagiotis Z., Athina G., Marina S., Jasmina G., . Bioorg. Med. Chem.. 2008;16:1160-1161.

[8] Koster R., Anderson M., Debeer E., . Fed. Proc. Fed. Am. Soc. Exp. Biol.. 1959;18:412-413.

[9] Kucukguzel I., Esra T., Guniz Kucukguzel S., Rollas S., De Clercq E., . Eur. J. Med. Chem.. 2008;43:381-392.

[10] Latifeh N., Hamed S., Khosrou A., Mohsen A., Mohammad H., Ghahremani R., . Bioorg. Med. Chem.. 2006;14:2507-2517.

[11] Lombardino G., . Nonsteroidal Antiinflammatory Drugs. New York: Wiley Interscience, John Wiley and Sons; 1985. pp. 3–15

[12] Maddi V., Raghu K.S., Rao M.N.A., . J. Pharm. Sci.. 1992;81:964-966.

[13] Mahendra R.S., Kiran K.M., Hanimi R.G., Tatikonda S., Chakravarthy A.K., Dolly P., . Bioorg. Med. Chem.. 2007;15:3997-4008.

[14] Mullican M.D., Wilson M.W., Connor D.T., Kostlan C.R., Schrier D.J., Dyer D., . J. Med. Chem.. 1993;36:1902-1909.

[15] OCED/OCDC, OECD, October 2000. Guidelines for testing of chemicals. Revised draft guidelines 423, acute oral toxicity class method, Revised document.

[16] Olcay B., Bahittin K., Murat K., . Turk. J. Chem.. 2006;30:29-40.

[17] Osiri M., Moreland L.W., . Arthitis Care Res.. 1999;12:351-362.

[18] Rainsford K.D., . Gut. 1975;16:514-527.

[19] Ronad P.M., Hunashal R.D., Satyanarayana D., Maddi V.S., . Arzneim. Forsch. (Drug Res.). 2008;58:641-646.

[20] Ronad P.M., Satyanarayana D., Hunashal R.D., Maddi V.S., . Arch. Pharm. Chem. Life Sci.. 2008;341:696-700.

[21] Upadhaya R.S., Sinha N., Jain S., Kishore N., Chandra R., Arora S., . Bioorg. Med. Chem.. 2004;12:2225-2228.

[22] Winter C.A., Risley E.A., Nuss G.W., . Proc. Soc. Exp. Biol. Med.. 1962;111:544-547.

[23] Yasemin D., Bilge C., Esra K., Fethi S., Ningur N., . Turk. J. Chem.. 2007;31:1-13.

Compd. No.	R	R¹	Yield (%)	Melting Point^∗ (⁰C)	R_f Value^#	Mol. Formula	Analysis (%)
							Found (Calculated)
							C	H	N
2a	H	4-CH₃	67.0	202-204	0.36	C₁₇H₁₆N₄OS	62.92	4.95	17.29
2a	H	4-CH₃	67.0	202-204	0.36	C₁₇H₁₆N₄OS	(62.94)	(4.97)	(17.27)
2b	2,4-Cl	4-NO₂	68.2	186-188	0.42	C₁₆H₁₁Cl₂N₅O₃S	45.33	2.65	16.53
2b	2,4-Cl	4-NO₂	68.2	186-188	0.42	C₁₆H₁₁Cl₂N₅O₃S	(45.30)	(2.61)	(16.51)
2c	2,4-Cl	4-OCH₃	65.0	189-191	0.36	C₁₇H₁₄Cl₂N₄O₂S	49.88	3.44	13.67
2c	2,4-Cl	4-OCH₃	65.0	189-191	0.36	C₁₇H₁₄Cl₂N₄O₂S	(49.89)	(3.45)	(13.69)
2d	2,4-Cl	2-OH	65.0	202-204	0.28	C₁₆H₁₂Cl₂N₄O₂S	48.63	3.07	14.16
2d	2,4-Cl	2-OH	65.0	202-204	0.28	C₁₆H₁₂Cl₂N₄O₂S	(48.62)	(3.06)	(14.17)
2e	2,4-Cl	2,4-Cl	61.0	180-182	0.24	C₁₆H₁₀Cl₄N₄OS	42.85	2.23	12.52
2e	2,4-Cl	2,4-Cl	61.0	180-182	0.24	C₁₆H₁₀Cl₄N₄OS	(42.88)	(2.25)	(12.50)
2f	2,4-Cl	4-Cl	66.8	198-200	0.16	C₁₆H₁₁Cl₃N₄OS	46.44	2.65	13.53
2f	2,4-Cl	4-Cl	66.8	198-200	0.16	C₁₆H₁₁Cl₃N₄OS	(46.45)	(2.68)	(13.54)
2g	2,4-Cl	4-CH₃	63.0	170-172	0.22	C₁₇H₁₄Cl₂N₄OS	51.91	3.57	14.21
2g	2,4-Cl	4-CH₃	63.0	170-172	0.22	C₁₇H₁₄Cl₂N₄OS	(51.92)	(3.59)	(14.25)
3a	H	4-NO₂	63.0	148-150	0.29	C₁₈H₁₅N₅O₅S	52.31	3.65	16.92
3a	H	4-NO₂	63.0	148-150	0.29	C₁₈H₁₅N₅O₅S	(52.30)	(3.66)	(16.94)
3b	H	4-OCH₃	69.0	199-201	0.46	C₁₉H₁₈N₄O₄S	57.25	4.53	14.07
3b	H	4-OCH₃	69.0	199-201	0.46	C₁₉H₁₈N₄O₄S	(57.27)	(4.55)	(14.06)
3c	H	2- OH	71.1	210-212	0.36	C₁₈H₁₆N₄O₄S	56.26	4.23	14.56
3c	H	2- OH	71.1	210-212	0.36	C₁₈H₁₆N₄O₄S	(56.24)	(4.20)	(14.57)
3d	H	2,4-Cl	70.0	158-160	0.42	C₁₈H₁₄Cl₂N₄O₃S	49.46	3.21	12.83
3d	H	2,4-Cl	70.0	158-160	0.42	C₁₈H₁₄Cl₂N₄O₃S	(49.44)	(3.23)	(12.81)
3e	H	4-Cl	72.2	186-188	0.43	C₁₈H₁₅ClN₄O₃S	53.69	3.74	13.94
3e	H	4-Cl	72.2	186-188	0.43	C₁₈H₁₅ClN₄O₃S	(53.67)	(3.75)	(13.91)
3f	H	4-CH₃	68.4	175-177	0.33	C₁₉H₁₈N₄O₃S	59.68	4.73	14.64
3f	H	4-CH₃	68.4	175-177	0.33	C₁₉H₁₈N₄O₃S	(59.67)	(4.74)	(14.65)
3g	2,4-Cl	4-NO₂	67.0	160-162	0.41	C₁₈H₁₃Cl₂N₅O₅S	44.84	2.70	14.56
3g	2,4-Cl	4-NO₂	67.0	160-162	0.41	C₁₈H₁₃Cl₂N₅O₅S	(44.83)	(2.72)	(14.52)
3h	2,4-Cl	4-OCH₃	67.2	190-192	0.34	C₁₉H₁₆Cl₂N₄O₄S	48.85	3.42	11.98
3h	2,4-Cl	4-OCH₃	67.2	190-192	0.34	C₁₉H₁₆Cl₂N₄O₄S	(48.83)	(3.45)	(11.99)
3i	2,4-Cl	2- OH	65.2	182-184	0.45	C₁₈H₁₄Cl₂N₄O₄S	47.68	3.13	12.37
3i	2,4-Cl	2- OH	65.2	182-184	0.45	C₁₈H₁₄Cl₂N₄O₄S	(47.69)	(3.11)	(12.36)
3j	2,4-Cl	2,4-Cl	68.4	178-180	0.36	C₁₈H₁₂Cl₄N₄O₃S	42.72	2.42	11.05
3j	2,4-Cl	2,4-Cl	68.4	178-180	0.36	C₁₈H₁₂Cl₄N₄O₃S	(42.71)	(2.39)	(11.07)
3k	2,4-Cl	4-Cl	68.5	204-206	0.42	C₁₈H₁₃Cl₃NO₃S	45.84	2.80	11.85
3k	2,4-Cl	4-Cl	68.5	204-206	0.42	C₁₈H₁₃Cl₃NO₃S	(45.83)	(2.78)	(11.88)
3l	2,4-Cl	4-CH₃	70.3	174-176	0.36	C₁₉H₁₆Cl₂N₄O₃S	50.59	3.56	12.44
3l	2,4-Cl	4-CH₃	70.3	174-176	0.36	C₁₉H₁₆Cl₂N₄O₃S	(50.56)	(3.57)	(12.41)

Synthesis, anti-inflammatory and analgesic activity of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid derivatives

Abstract

Keywords

1,2,4-Triazole

Schiff Base

1,2,4-Triazolyl thioacetic acid

Anti-inflammatory activity

Analgesic activity

1 Introduction

2 Experimental

2.1 General considerations

2.2 Synthesis

2.2.1 General method for synthesis of 3-(substituted phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1)

2.2.1.1 3-(Phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1a)

2.2.1.2 3-(2,4-Dichloro phenoxymethyl)-4-amino-5-mercapto 1,2,4-triazole (1b)

2.2.2 General method for synthesis of 4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-2H-1,2,4-triazole-3(4H)-thione (2a–g)

2.2.2.1 4-(4-Methylbenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazolo-3-thiol (2a)

2.2.2.2 4-(4-Nitrobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2b)

2.2.2.3 4-(4-Methoxyoxybenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2c)

2.2.2.4 4-(2-Hydroxybenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2d)

2.2.2.5 4-(2,4-Dichlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2e)

2.2.2.6 4-(4-Chlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2f)

2.2.2.7 4-(4-Methylbenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-2H-1,2,4-triazolo-3(4H)-thione (2g)

2.2.3 General method for synthesis of 2-[4-(substituted benzylideneamino)-5-(substituted phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3a–l)

2.2.3.1 2-[4-(4-Nitrobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3a)

2.2.3.2 2-[4-(4-Methoxybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3b)

2.2.3.3 2-[4-(4-Methylybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3c)

2.2.3.4 2-[4-(2,4-Dichlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3d)

2.2.3.5 2-[4-(4-Chlorobenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3e)

2.2.3.6 2-[4-(2-Hydroxybenzylideneamino)-5-(phenoxymethyl)-4H-1,2,4-triazol-3-yl thio] acetic acid (3f)

2.2.3.7 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-nitrobenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3g)

2.2.3.8 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-methoxybenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3h)

2.2.3.9 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(2-hydroxybenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3i)

2.2.3.10 2-{4-(2,4-Dichlorobenzylideneamino)-5-[(2,4-dichlorophenoxy)methyl]-4H-1,2,4-triazol-3-yl thio} acetic acid (3j)

2.2.3.11 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-chlorobenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3k)

2.2.3.12 2-{5-[(2,4-Dichlorophenoxy)methyl]-4-(4-methylbenzylideneamino)-4H-1,2,4-triazol-3-yl thio} acetic acid (3l)

3 Pharmacological screening

3.1 Animals

3.2 Acute toxicity

3.3 In vivo anti-inflammatory activity

3.4 Analgesic activity (Koster et al., 1959)

3.5 Gastric ulceration (Alich et al., 1983)

3.6 Statistical analysis

4 Results and discussion

5 Conclusion

Conflict of interest statements

Acknowledgements

References

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