Synthesis of some new 2-(6-methoxy-2-naphthyl)- 5-aryl-1,3,4-oxadiazoles as possible non-steroidal anti-inflammatory and analgesic agents

The synthesis of some new 2-(6-methoxy-2-naphthyl)-5-aryl-1,3,4-oxadiazoles (4a-k) has been described. Ethyl-6-methoxy-2-naphthoate (1) yielded on treatment with hydrazine hydrate to 6-methoxy-2-naphthoic acid hydrazide (2). Compound 2 reacted with substituted aromatic carboxylic acids (3a-k) in phosphorus oxychloride yielded 2-(6-methoxy-2-naphthyl)-5-aryl-1,3,4-oxadiazoles (4a-k). Newly synthesized compounds were characterized by IR, (1)H-NMR and mass spectral data. All the compounds were screened for their anti-inflammatory and analgesic activity. Compound 4j exhibited promising anti-inflammatory and analgesic activities.     

Synthesis of some new 2-(substituted-phenyl)-5-(N,N-diphenylaminomethyl)-1,3,4-oxadiazoles: a safer anti-inflammatory and analgesic agents

A series of 2-(substituted-phenyl)-5-(N,N-diphenylaminomethyl)-1,3,4-oxadiazoles (3-15) were synthesized. The compounds were evaluated for their anti-inflammatory, analgesic, ulcerogenic and lipid peroxidation actions. The percentage inhibition in edema at different time intervals indicated that compounds 8, 11, 12, 14 and 15 exhibited good anti-inflammatory potential. The results illustrate that 2-(2-acetoxyphenyl)-5-(N,N-diphenylaminomethyl)-1,3,4-oxadiazole (15) and 2-(3,4-dimethoxyphenyl)-5-(N,N-diphenylaminomethyl)-1,3,4-oxadiazole (12) showed best anti-inflammatory activity among the series tested. Furthermore, activity is higher in case of chloro substitution as compared to methyl substitution. The compounds synthesized were also evaluated for their ulcerogenic and lipid peroxidation action and showed superior GI safety profile along with reduction in lipid peroxidation as compared to that of ibuprofen.     

Synthesis of some new 2-(2-fluoro-4-biphenylyl)propionic acid derivatives as potential anti-inflammatory agents

The synthesis of a group of 1,3,4-oxadiazoles, 1,2,4-triazoles, 1,3,4-thiadiazoles and 1,2,4-triazine derived from 2-(2-fluoro-4-biphenylyl) propionic acid is described. The structures of new compounds are supported by IR, 1H NMR and MS data. These compounds were tested in vivo for their anti-inflammatory activity. The compounds which showed activity comparable to the standard drug flurbiprofen, were screened for their analgesic, ulcerogenic and lipid peroxidation activities. Five out of seventeen new compounds, showed very good anti-inflammatory activity in the carrageenan induced rat paw edema test with negligible ulcerogenic action. The compounds, which showed less ulcerogenic action, also showed reduced malondialdehyde production (MDA), which is one of the byproducts of lipid peroxidation. The study showed that the compounds inhibit the induction of gastric mucosal lesions and it can be suggested from our results that their protective effects may be related to an inhibition of lipid peroxidation in the gastric mucosa.     

Synthesis and pharmacological evaluation of N-(6-chlorobenzo[d]thiazol-2-yl)hydrazine carboxamide derivatives of benzothiazole

A series of 6-substituted-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole (6a–g) and 1,3,4-oxadiazole (7a–g, 8) derivatives of benzothiazole were synthesized in satisfactory yield and pharmacologically evaluated for their anti-inflammatory, analgesic, ulcerogenic, and lipid peroxidation activities by known experimental models. All the synthesized compounds were in good agreement with elemental and spectral data. Some of the synthesized compounds have significant anti-inflammatory and analgesic activities. Ulcerogenic and irritative action on the gastrointestinal mucosa, in comparison with standard are low.     

Studies on fused heterocyclic 3,6-disubstituted-1,2,4-triazolo-1,3,4-thiadiazoles: synthesis and biological evaluation

In this study, a series of 3,6-disubstituted-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazoles (5a–t) were synthesized by condensing 4-amino-3-mercapto-(4H)-1,2,4-triazoles (4a–c) with different aromatic or aroyl acids through one-pot reaction. The compounds were evaluated for their anti-inflammatory, analgesic, ulcerogenic, and lipid peroxidation actions. Some of the newly synthesized compounds showed very good anti-inflammatory activity with low GI toxicity and reduced lipid peroxidation. These compounds also showed interesting profile of analgesic activity in acetic acid-induced writhing test. The findings of the study indicate that the synthesized compounds have superior GI safety profile along with reduction in lipid peroxidation as compared to that of the standard.     

Synthesis and Biological Evaluation of ��-Aroylpropionic acid based 1,3,4-Oxadiazoles

In the present investigation, two new series, 1-(4-benzylphenyl)-3-(5-substituted-1,3,4-oxadiazol-2-yl)-1-propanone and 1-(4-ethylphenyl)-3-(5-substituted-1,3,4-oxadiazol-2-yl)-1-propanone from β-(4-benzylbenzoyl)propionic acid and β-(4-ethylbenzoyl)propionic acid, respectively, were synthesized and tested for antiinflammatory, analgesic, lipid peroxidation, ulcerogenic and antibacterial actions. A fair number of compounds were found to have good antiinflammatory activity in carrageenan-induced rat paw edema test, while a few compounds showed significant antibacterial activity. The newly synthesized compounds showed very low ulcerogenic action.     

2-Amino-5-sulfanyl-1,3,4-thiadiazoles: a novel series of anti-inflammatory and analgesic agents

2-Amino-5-sulfanyl-1,3,4-thiadiazole derivatives were synthesized via the interaction of 2-amino-5-sulfanyl-1,3,4-thiadiazole, Ar-Cl, and benzene sulfonamide/benzene sulfonyl chloride. Twelve compounds were synthesized, out of which six compounds show significant anti-inflammatory and analgesic activity and were devoid of gastrointestinal side effects (ulcerogenic effect), which zre the most frequent adverse reactions associated with orally ingested anti-inflammatory or antiarthritic agents.     

Synthesis,analgesic and anti-inflammatory activities of new methyl-imidazolyl-1,3,4-oxadiazoles and 1,2,4-triazoles

Background

Long-term clinical employment of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with significant side effects including gastrointestinal (GI) lesions and kidney toxicity. In this paper we designed and synthesized new imidazolyl-1,3,4-oxadiazoles and 1,2,4-triazoles by molecular hybridization of previously described anti-inflammatory compounds in the hope of obtaining new safer analgesic and anti-inflammatory agents.

Methods

The target structures were synthesized by preparation of 5-methyl-1H-imidazole-4-carboxylic acid ethyl ester 5. The reaction of hydrazine hydrate with this ester afforded the 5-methyl-1H-imidazole-4-carboxylic acid hydrazide 6 which was converted to target compounds 7-15 according to the known procedures. In silico toxicity risk assessment and drug likeness predictions were done, in order to consider the privileges of the synthesized structures as drug candidates.

Results and discussion

The analgesic and anti-inflammatory profile of the synthesized compounds were evaluated by writhing and carrageenan induced rat paw edema tests respectively. Compounds 8, 9 and 11-13 and 15 were active analgesic agents and compounds 8, 9 and 11-13 showed significant anti-inflammatory response in comparison with control. Compounds 11 and 13 were screened for their ulcerogenic activities and none of them showed significant ulcerogenic activity. The active Compounds 11 and 12 showed the highest drug likeness and drug score.

Conclusions

The analgesic and anti-inflammatory activities of title compounds were comparable to that of standard drug indomethacin with a safer profile of activity. The results revealed that both of oxadiazole and triazole scaffolds can be determined as pharmacophores. The in silico predictions and pharmacological evaluations showed that compounds 11 and 12 can be chosen as lead for further investigations.     

Anti-inflammatory and gastro sparing activity of some new indomethacin derivatives

Indomethacin is a non-steroidal anti-inflammatory drug but its use is associated with high degree of gastric toxicity therefore it is prescribed only in severe conditions. In order to reduce the gastric toxicity of indomethacin, various oxadiazole, triazole, thiadiazole and triazine derivatives have been synthesized. Out of thirteen cyclized derivatives, eleven were screened for anti-inflammatory activity by Winter et al. method. Four compounds showed highly significant activity and were further tested for analgesic, ulcerogenic and lipid peroxidation activities. The tested compounds showed anti-inflammatory activities in the range from about 32% to 85% as compared to that of indomethacin of about 96%. The compounds showing high anti-inflammatory activity also exhibited reduction in severity index. These compounds also produced less malondialdehyde content in gastric mucosa than the standard drug indomethacin. The study showed that the compounds inhibited the induction of gastric mucosal lesions and it can be suggested from our results that their protective effects may be related to inhibition of lipid peroxidation in the gastric mucosa.     

Synthesis and analgesic and antiinflammatory activity of methyl 6-substituted-3(2h)-pyridazinone-2-ylacetate derivatives

A series of methyl 6-substituted-3(2H)-pyridazinone-2-ylacetates 9 were synthesized and their analgesic and anti-inflammatory effects were evaluated in the phenylbenzoquinone-induced writhing test (PBQ test) and carrageenan-induced paw edema method, respectively. Side effects of the compounds were examined on gastric mucosa. None of the compounds showed gastric ulcerogenic effect compared with reference nonsteroidal anti-inflammatory drugs. Methyl 6-(4-(4-fluorophenyl)piperazine)-3(2H)-pyridazinone-2-ylacetate 9e was found to be more active than acetylsalicylic acid (ASA). Methyl 6-(4-(2-ethoxyphenyl)piperazine)-3(2H)-pyridazinone-2-ylacetate 9c has shown an anti-inflammatory activity as compared to the standard compound indometacin at the carrageenan-induced paw edema method.A significant dependence of the anti-inflammatory effect on the substituents has been observed. The pharmacological study of these compounds confirms that modification of the chemical group at the position 6 of the 3(2H)-pyridazinone system influences analgesic and anti-inflammatory activities. The structures of these new pyridazinone derivatives were confirmed by their IR and (1)H-NMR spectra and elemental analysis.     

Synthesis of novel 3-butyl-2-substituted amino-3H-quinazolin-4-ones as analgesic and anti-inflammatory agents

A variety of novel 3-butyl-2-substituted amino-3H-quinazolin-4-ones were synthesized by reacting the amino group of 3-butyl-2-hydrazino-3H-quinazolin-4-one with various aldehydes and ketones. The title compounds were investigated for analgesic, anti-inflammatory and ulcerogenic index activities. The compound 3-butyl-2-(1-methylbutylidene-hydrazino)-3H-quinazolin-4-one (AS3) emerged as the most active analgesic agent. Compound 3-butyl-2-(1-ethylpropylidene-hydrazino)-3H-quinazolin-4-one (AS2) emerged as the most active anti-inflammatory agent and is moderately more potent when compared to the reference standard diclofenac sodium. Interestingly, the test compounds showed only mild ulcerogenic potential when compared to aspirin.     

Synthesis and pharmacological evaluation of some 3-(4-methylphenyl)-2-substituted amino-3H-quinazolin-4-ones as analgesic and anti-inflammatory agents

A variety of 3-(4-methyl phenyl)-2-substituted amino-3H-quinazolin-4-ones were synthesized by reacting the amino group of 2-hydrazino-3-(4-methyl phenyl)-3H-quinazolin-4-one with a variety of aldehydes and ketones. The starting material 2-hydrazino-3-(4-methyl phenyl)-3H-quinazolin-4-one was synthesized from 4-methyl aniline. The title compounds were investigated for analgesic, anti-inflammatory, and ulcerogenic index activities. While the test compounds exhibited significant activity, compounds Al, A2, and A3 showed more potent analgesic activity and the compound A3 showed more potent anti-inflammatory activity when compared to the reference standard diclofenac sodium. Interestingly, the test compounds showed only mild ulcerogenic potential when compared to aspirin.     

A study of anti-inflammatory activity of some novel alpha-amino naphthalene and beta-amino naphthalene derivatives

In the present study, some naphthalene derivatives have been synthesized by incorporating azetidinyl and thiazolidinyl moieties at its alpha- or beta-positions such as alpha-(3-chloro-2-oxo-4-substituted)aryl-1-azetidinyl)naphthalenes 6-10, alpha-((substituted)aryl-4-oxo-1,3-thiazolidin-3-yl)naphthalenes 11-15, beta-(3-chloro-2-oxo-4-substituted aryl-1-azetidinyl)naphthalenes 21-25, and beta-(substituted aryl-4-oxo-1,3-thiazolidin-3-yl)naphthalenes 26-30. These compounds have also been screened for acute toxicity and anti-inflammatory and analgesic activities. Compounds which showed better anti-inflammatory and analgesic activities were also examined for their ulcerogenic liability and underwent a cyclooxygenase assay. Two compounds, 12 and 28, were found to exhibit potent anti-inflammatory activity as compared to the standard drugs phenylbutazone and naproxen.     

Synthesis and Evaluation of Antiinflammatory, Analgesic and Ulcerogenic Potential of NSAIDs Bearing 1,3,4-Oxadiazole Scaffold

Synthesis of 1,3,4-oxadiazole derivatives of diclofenac and mefenamic acid are described. The target compounds 5-[2-(2,6-dichloroanilino)benzyl]-2-aryl-1,3,4-oxadiazole (3a-3e) and 5-[2-(2,3-dimethylanilino)phenyl]-2-(aryl)-1,3,4-oxadiazole (6a-6e) were obtained by treating 2 and 5 with various aromatic acids using POCl₃ as dehydrating agent. They were purified and characterized by IR, ¹H-NMR and elemental analysis. These compounds were further subjected to antiinflammatory, analgesic and acute ulcerogenic activity. Compound 3c and 6d exhibited good antiinflammatory activity and compounds 3c, 3e, 6c, 6d, 6e were found to be non ulcerogenic.     

Novel 3,6‐Disubstituted 7H‐1,2,4‐Triazolo[3,4‐b][1,3,4]thiadiazines: Synthesis,Characterization, and Evaluation of Analgesic / Anti‐inflammatory,Antioxidant Activities

In this study, the synthesis of a new series of 3,6‐disubstituted‐7H‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazine 1a – 4c compounds derived from 4‐amino‐3‐substituted‐1,2,4‐triazole‐5‐thiones 1 – 4 is described. All of the synthesized compounds were screened for their possible analgesic / anti‐inflammatory, antioxidant activities and gastric toxicity. The compound 2c was found to have both significant analgesic and consistent anti‐inflammatory activity without inducing any gastric lesions along with minimal lipid peroxidation. A deep insight into the structures of the active compounds revealed that the compounds carrying an electron withdrawing group (a chloride or fluoride) on the phenyl ring at 6‐position of the condensed heterocyclic derivatives exhibited noticeable higher activity.     

Synthesis and evaluation of anti-inflammatory and analgesic activity of 3-[(5-substituted-1,3,4-oxadiazol-2-yl-thio)acetyl]-2H-chromen-2-ones

A novel series of 3-[(5-substituted-1,3,4-oxadiazol-2-yl-thio)acetyl]-2H-chromen-2-one (7a–i) were synthesized by the condensation between the appropriately substituted 5-substituted-1,3,4-oxadiazolyl-2-thione (4a–i) derived from various existing NSAIDs and 3-(2-bromoacetyl)-2H-chromen-2-one (6) under reflux in the presence of sodium ethoxide. Structure of the synthesized compounds was established on the basis of physicochemical, elemental analysis, and spectral data. The title compounds were screened for in vivo acute anti-inflammatory and analgesic activities at a dose of 200 mg/kg bw. Among the series, four compounds 7c, 7e, 7f, and 7h were found to possess a significant anti-inflammatory and analgesic activity profile. In addition, these compounds were also found to possess a less degree of ulcerogenic potential as compared to standard NSAIDs.     

Synthesis and evaluation of the analgesic and anti-inflammatory activity of new 3(2H)-pyridazinone derivatives

A series of 6-substituted-3(2H)-pyridazinone derivatives were synthesized and evaluated for analgesic and anti-inflammatory activities. The structures of these new pyridazinone derivatives were confirmed by their IR, 1H-NMR spectra and elementary analysis. Analgesic and anti-inflammatory activities of the title compounds have been evaluated. Four of the ten tested compounds possessed significant analgesic effects in the phenylbenzoquinone-induced writhing test (PBQ test). The most active derivatives 8a, 8b, 8d, 8e were void of gastric ulcerogenic effect or acute toxicity at the maximal dose (200 mg/kg p.o.). In the carrageenan-induced paw edema model, compound 8d (6- [4- (2-fluorophenyl) piperazin-1-yl]-3(2H)-pyridazinone) showed anti-inflammatory activity similar to that of the standard drug indometacin (CAS 53-86-1). A significant dependence of the anti-inflammatory effect on the substituents was observed; The pharmacological study of these compounds confirms that modification of the chemical group at position 6 of the 3(2H)-pyridazinone ring influences analgesic and anti-inflammatory activities.     

Synthesis and pharmacological evaluation of novel quinoxalines as potential nonulcerogenic anti-inflammatory and analgesic agents

Some new substituted quinoxaline and furo[2,3-b]quinoxaline derivatives have been synthesized and tested for their anti-inflammatory and analgesic activities and for their ulcerogenic potential. The pharmacological evaluation of selected synthesized compounds revealed that 5a was equipotent and compounds 3, 4b, 4e and 5b possessed strong anti-inflammatory activity in chronic inflammatory models compared with indometacin (CAS 53-86-1) as reference drug. In addition, compound 4a was the safest one and the others showed little ulcerogenic activity. All the tested compounds showed moderate analgesic activity compared to the reference drug.     

Design and one-pot and microwave-assisted synthesis of 2-amino/5-aryl-1,3,4-oxadiazoles bearing a benzimidazole moiety as antioxidants

In this study, two new series of 2-amino-1,3,4-oxadiazoles and 5-aryl-1,3,4-oxadiazoles carrying a benzimidazole moiety were synthesized. The antioxidant properties of these compounds were investigated in vitro by the determination of the microsomal NADPH-dependent inhibition of lipid peroxidation levels (LP), the microsomal ethoxyresorufin O-deethylase activity (EROD), and DPPH radical scavenger effects. Among the tested compounds, 2-[(2-(4-chlorophenyl)-1H-benzo[d]imidazole-1-yl)methyl]-5-(4-fluorophenyl)-1,3,4-oxadiazole (9) was found to be the most active compound in all three in vitro systems.     

Design and synthesis of some thiazolotriazolyl esters as anti-inflammatory and analgesic agents

In order to develop potent analgesic/anti-inflammatory compounds with reduced ulcerogenic risk, a series of thiazolotriazolyl-carboxylic and acetic acid esters were synthesized and characterized by spectral and elementary analysis. All synthesized compounds were screened for in vivo anti-inflammatory activities in mice by carregeenan-induced paw edema model. The compounds showing 20% reduction in paw edema were also evaluated for their analgesic activities by acetic acid-induced writhing test and the gastric ulceration risk by determining the lipid peroxidation level in stomachs. Among the compounds tested, compounds 1, 4, 6, 7, 8, 1a, 2a, 3a, 4a, 7a, 2b, and 8b showed moderate-to-good anti-inflammatory activity at various doses in any of the measurement intervals. Compounds 7a, 2b, and 8b were the most actives of the series in analgesic activity test. Moreover, compounds 1, 4, and 8 were found to be safe in stomach in respect of free radical production.