Relative inhibitory activity of bile acids against 12‐O‐tetradecanoylphorbol‐13‐acetate‐induced inflammation,and chenodeoxycholic acid inhibition of tumour promotion in mouse skin two‐stage carcinogenesis

Objectives Bile acids are present in Bezoar Bovis and Fel Ursi, traditionally used as antipyretics and antispasmodics. However the anti‐inflammatory activity of individual bile acids and related compounds has not yet been investigated. In this paper, we report the structure–activity relationships influencing the anti‐inflammatory activity of a variety of structurally different bile acid derivatives and also the inhibitory activity of chenodeoxy‐cholic acid against tumour promotion. Methods Fifty derivatives of bile acids were examined for their inhibitory activity against the induction of oedema in mouse ear by application of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA). Also, the effect of chenodeoxycholic acid was studied in mouse skin in which tumours had been induced by topical application of 7,12‐dimethylbenz[a]anthracene (DMBA) and promoted by TPA. Key findings Many bile acid derivatives had an inhibitory effect against TPA‐induced ear oedema at a similar grade to that of indometacin. Chenodeoxycholic acid, methyl 3α,7α,15α‐trihydroxy‐5β‐cholan‐24‐oate and methyl 3α,7α,15β‐trihydroxy‐5β‐cholan‐24‐oate showed the most potent activity with an ID50 value of 71–110 nmol/ear, a level corresponding to that of hydrocortisone (69 nmol/ear). Furthermore, chenodeoxycholic acid markedly suppressed tumour‐promoting activity by TPA following initiation by DMBA in mouse skin. Conclusions This is the first report on the anti‐inflammatory activity of bile acids on TPA‐induced inflammatory ear oedema in mice. Chenodeoxycholic acid, methyl 3α,7α,15α‐trihydroxy‐5β‐cholan‐24‐oate and methyl 3α,7α,15β‐trihydroxy‐5β‐cholan‐24‐oate showed the most potent activity, at a level corresponding to that of hydrocortisone. Furthermore, chenodeoxycholic acid markedly inhibited tumour promotion in a two‐stage carcinogenesis model in mouse skin.     

Synthesis and in‐vitro Antimycobacterial Evaluation of 1‐(Cyclopropyl/2,4‐difluorophenyl/tert‐butyl)‐1,4‐dihydro‐ 8‐methyl‐6‐nitro‐4‐oxo‐7‐(substituted secondary amino)quinoline‐3‐carboxylic acids

Fifty one newer 1‐(cyclopropyl/2,4‐difluorophenyl/tert‐butyl)‐1,4‐dihydro‐8‐methyl‐6‐nitro‐4‐oxo‐7‐(substituted secondary amino)quinoline‐3‐carboxylic acids were synthesized from 1,3‐dichloro‐2‐methylbenzene and evaluated for in‐vitro antimycobacterial activities against Mycobacterium tuberculosis H37Rv (MTB), multi‐drug resistant Mycobacterium tuberculosis (MDR‐TB), and Mycobacterium smegmatis (MC²). Among the synthesized compounds, 1‐cyclopropyl‐1,4‐dihydro‐7‐(3,4‐dihydro‐6,7‐dimethoxyisoquinolin‐2(1H)‐yl)‐8‐methyl‐6‐nitro‐4‐oxoquinoline‐3‐carboxylic acid 9p was found to be the most active compound in vitro with a MIC value of 0.39 μM against MTB. Against MDR‐TB, compound 7‐(2‐carboxy‐5,6‐dihydroimidazo[1,2‐a]pyrazin‐7(8H)‐yl)‐1‐cyclopropyl‐1,4‐dihydro‐8‐methyl‐6‐nitro‐4‐oxoquinoline‐3‐carboxylic acid 9n was found to be the most active with a MIC value of 0.09 μM.     

Synthesis and Antitubercular Screening of [(2‐Chloroquinolin‐3‐yl)methyl] Thiocarbamide Derivatives

A series of 1‐(substituted‐phenyl)‐1‐[(2‐chloroquinolin‐3‐yl)methyl]thiocarbamide and 1‐(substituted‐phenyl)‐1‐[(2‐chloroquinolin‐3‐yl)methyl]methylthiocarbamide derivatives was synthesized as antitubercular agent. The structure of quinolinyl amines and their thiocarbamide derivatives were established on the basis of IR, ¹H and ¹³C‐NMR and mass spectral data. All the compounds were tested in vitro for antimycobacterial activity against Mycobacterium tuberculosis (ATCC‐25177) in Lowenstein‐Jensen medium by well diffusion method and MIC by twofold serial dilution method. Results of the antitubercular screening revealed that compounds showed moderate to good antitubercular activity. Compound having two halogens in the phenyl rings viz. 3g , 3h , 4g, and 4h exhibited MIC of 50 μg/mL. The computational parameters relevant to absorption and permeation of target compounds were also calculated and found to be well correlated with antitubercular activity.     

2‐Aryl‐3‐(1H‐Azol‐1‐yl)‐1H‐Indole Derivatives: A New Class of Antimycobacterial Compounds – Conventional Heating in Comparison with MW‐Assisted Synthesis

2‐Aryl‐3‐(1H‐imidazol‐1‐yl and 1H‐1,2,4‐triazol‐1‐yl)‐1H‐indole derivatives were synthesized and tested for their in‐vitro antifungal and antimycobacterial activities. These indole derivatives were devoid of antifungal activity against the tested strains of Candida spp. Yet, they exhibited an interesting antitubercular activity against Mycobacterium tuberculosis reference strain H₃₇Rv.     

Antibacterial activity of 15‐residue lactoferricin derivatives

Abstract: Lactoferricins are a class of antibacterial peptides isolated after gastric‐pepsin digest of the mammalian iron‐chelating‐protein lactoferrin. For investigation of antibacterial activity, we prepared short synthetic derivatives of bovine, human, caprine, murine and porcine lactoferricins with 15‐amino‐acid residues of high sequence homology. The peptides corresponded to amino‐acid residues 17–31 of the mature bovine lactoferrin. Only the bovine and caprine derivatives displayed measurable antibacterial activity, with the bovine one having a minimal inhibitory concentration of 24 µm and being 10 times more active than the caprine one against Escherichia coli. An alanine‐scan of the bovine lactoferricin derivative was performed to identify specific amino acids that were important for the antibacterial activity. We found that neither of the two tryptophan residues (Trp 6 and Trp 8) present in the bovine lactoferricin derivative could be replaced by alanine without a major loss of antibacterial activity. The other lactoferricin derivatives tested contained only one tryptophan residue (Trp 6). Modified human, caprine and porcine lactoferricin derivatives containing two tryptophan residues (Trp 6 and Trp 8) displayed minimal inhibitory concentrations of 74, 174 and 219 µm , respectively, which represented up to a six‐fold increase in antibacterial activity. The alanine‐scan also revealed that the antibacterial activity was increased when acetamidomethyl‐protected cysteine and unprotected glutamine (Cys 3 and Gln 7) were replaced with alanine. Only the bovine lactoferricin derivative and a few of its alanine‐modified derivatives displayed measurable activity against Staphylococcus aureus.     

Synthesis and mycobacterial evaluation of 5‐substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido‐[2,3‐d]pyrimidin‐4(3H)‐one derivatives

5‐Substituted‐6‐acetyl‐2‐amino‐7‐methyl‐5,8‐dihydropyrido[2,3‐d]pyrimidin‐4(3H)‐one derivatives were synthesized and evaluated against Mycobacterium tuberculosis H37Rv, Mycobacterium aurum, Escherichia coli, and Staphylococcus aureus as well as a human monocyte‐derived macrophage (THP‐1), and murine macrophage (RAW 264.7) cell lines to assess their antibacterial and cytotoxic potential, respectively. The compounds showed activity in the range of 1.95–125 µg/ml against M. tuberculosis but showed no activity against M. aurum, E. coli, and S. aureus, indicating selectivity towards slow‐growing mycobacterial pathogens. The compounds exhibited very low to no cytotoxicity up to 500 µg/ml concentration against eukaryotic cell lines. The most potent molecule, 2l , showed a minimum inhibitory concentration of 1.95 µg/ml against M. tuberculosis H37Rv and a selectivity index of >250 against both the eukaryotic cell lines. Furthermore, 2l showed moderate inhibition of whole‐cell mycobacterial drug‐efflux pumps when compared to verapamil, a known potent inhibitor of efflux pumps. Thus, derivative 2l was identified as an antituberculosis hit molecule, which could be used to yield more potent lead molecules.     

Immunomodulatory and Anticancer Activities of Some Novel 2‐Substituted‐6‐bromo‐3‐methylthiazolo[3,2‐a]benzimidazole Derivatives

Ethyl 6‐bromo‐3‐methyl‐1,3‐thiazolo[3,2‐a]benzimidazole‐2‐carboxylate 2 was prepared by the ambient temperature bromination of ethyl 3‐methyl‐1,3‐thiazolo[3,2‐a]benzimidazole‐2‐carboxylate 1 . The acid hydrazide 4 was obtained by the reaction of ester 2 with hydrazine hydrate. Treatment of compound 4 with benzaldehyde or 2‐thiophenaldehyde yielded the corresponding hydrazones 6a and 6b , respectively, while the reaction of acid hydrazide 4 with ethoxymethylene malononitrile ( 7a ) or with ethyl ethoxymethylene cyanoacetate ( 7b ) in refluxing ethanol afforded pyrazole derivatives 9a and 9b , respectively. Taken together, from the biological investigations compounds 9a and 9b were the most significant inhibitors of LPS‐stimulated NO generation from Raw murine macrophage 264.7, and, as another result, compounds 2 and 4 had a weak radical scavenging activity against DPPH radicals. Moreover, 2 , 4 , and 9a had a concomitant strong cytotoxicity against both colon carcinoma cells (HCT‐116) and hepatocellular carcinoma cells (Hep‐G2) while 9b showed specific cytotoxicity only against colon carcinoma cells.     

Amino Acid Derivatives,Part 4: Synthesis and Anti‐HIV Activity of New Naphthalene Derivatives

A new series of 2‐(naphthalen‐2‐yloxy)‐N‐[(aryl‐5‐thioxo‐4,5‐dihydro‐1H‐1,2,4‐triazol‐3‐yl)methyl] acetamides 5a–f was synthesized from naphthalene‐derived glycine derivative 2 via the hydrazinoacetamide analogs 4a–f . Alternatively, treatment of 4a with H₂SO₄ afforded 2‐(naphthalen‐2‐yloxy)‐N‐((5‐(phenylamino)‐1,3,4‐thiadiazol‐2‐yl)methyl) acetamide 6a . Alkylation or sulphonylation of 5a afforded the S‐alkylated derivatives 7 and 8 , respectively. Interestingly, treatment of 3 with methoxide ion gave the triazine derivative 9 . The synthesized compounds have been screened for their inhibitory activity against HIV‐1 and HIV‐2 in MT‐4 cells. However, 7 was found to be the potent inhibitor in vitro for the replication of HIV‐1 (EC₅₀ = 0.20 μg/mL), suggesting a new lead in the development of an antiviral agent.     

From β‐N‐tert‐butyloxycarbonyl N‐carboxyanhydrides to β‐aminoacid derivatives

Abstract: β‐N‐tert‐butyloxycarbonyl‐N‐carboxyanhydrides are very reactive β‐amino acid derivatives. They react cleanly and smoothly with different nucleophiles like aminoesters, enolates, N‐methyl‐d ‐glucamine, amidoximes to afford in good to excellent yields peptides, β‐amino ketocompounds, β‐aminosugars and functionalized disubstituted 1,2,4‐oxadiazoles.     

Drug Resistance Reversal Potential of Ursolic Acid Derivatives against Nalidixic Acid‐ and Multidrug‐resistant Escherichia coli

As a part of our drug discovery program, ursolic acid was chemically transformed into six semi‐synthetic derivatives, which were evaluated for their antibacterial and drug resistance reversal potential in combination with conventional antibiotic nalidixic acid against the nalidixic acid‐sensitive and nalidixic acid‐resistant strains of Escherichia coli. Although ursolic acid and its all semi‐synthetic derivatives did not show antibacterial activity of their own, but in combination, they significantly reduced the minimum inhibitory concentration of nalidixic acid up to eightfold. The 3‐O‐acetyl‐urs‐12‐en‐28‐isopropyl ester (UA‐4) and 3‐O‐acetyl‐urs‐12‐en‐28‐n‐butyl ester (UA‐5) derivatives of ursolic acid reduced the minimum inhibitory concentration of nalidixic acid by eightfold against nalidixic acid‐resistant and four and eightfold against nalidixic acid‐sensitive, respectively. The UA‐4 and UA‐5 were further evaluated for their synergy potential with another antibiotic tetracycline against the multidrug‐resistant clinical isolate of Escherichia coli‐KG4. The results showed that both these derivatives in combination with tetracycline reduced the cell viability in concentration‐dependent manner by significantly inhibiting efflux pump. This was further supported by the in silico binding affinity of UA‐4 and UA‐5 with efflux pump proteins. These ursolic acid derivatives may find their potential use as synergistic agents in the treatment of multidrug‐resistant Gram‐negative infections.     

Synthesis and Antimicrobial Evaluation of 6‐Alkylamino‐N‐phenylpyrazine‐2‐carboxamides

This work presents synthesis and antimicrobial evaluation of nineteen 6‐alkylamino‐N–phenylpyrazine‐2‐carboxamides. Antimycobacterial activity was determined against Mycobacterium tuberculosis H37Rv, M. kansasii and two strains of M. avium. Generally, the antimycobacterial activity increased with prolongation of simple alkyl chain and culminated in compounds with heptylamino substitution ( 3e , 4e ) with MIC = 5–10 μm against M. tuberculosis H37Rv. On the contrary, derivatives with modified alkyl chain (containing e.g. terminal methoxy or hydroxy group) as well as phenylalkylamino derivatives were mainly inactive. The most active compounds (with hexyl to octylamino substitution) were evaluated for their in vitro activity against drug‐resistant strains of M. tuberculosis and possessed activity comparable to that of the reference drug isoniazid. None of the tested compounds were active against M. avium. Some derivatives exhibited activity against Gram‐positive bacteria including methicillin‐resistant Staphylococcus aureus (best MIC = 7.8 μm ), while Gram‐negative strains as well as tested fungal strains were completely unsusceptible. Active compounds were tested for in vitro toxicity on various cell lines and in most cases were non‐toxic up to 100 μm .     

Preparation and in‐vitro Evaluation of 4‐Benzylsulfanylpyridine‐2‐carbohydrazides as Potential Antituberculosis Agents

A set of 4‐benzylsulfanylpyridine‐2‐carbohydrazides was synthesized and evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, non‐tuberculous mycobacteria, and multidrug‐resistant M. tuberculosis. The activities expressed as the minimum inhibitory concentration (MIC) fall into a range of 2 to 125 μmol/L, most often 4 to 32 μmol/L. The results revealed that the substituents on the benzyl moiety do not influence the antimycobacterial efficacy. The substances exhibited similar activities against sensitive and resistant strains of M. tuberculosis. Furthermore, compounds show low antiproliferative effect and cytotoxicity.     

Synthesis and Antimycobacterial Activity of Azetidine‐, Quinazoline‐, and Triazolo‐thiadiazole‐containing Pyrazines

The re‐emergence of tuberculosis (TB) as a global health problem over the past few decades, accompanied by the rise of drug‐resistant strains of Mycobacterium tuberculosis, emphasizes the need for the discovery of new therapeutic drugs against this disease. The emerging serious problem both in terms of TB control and clinical management prompted us to synthesize a novel series of N‐[2‐(substituted aryl)‐3‐chloro‐4‐oxoazetidin‐1‐yl]‐2‐(pyrazin‐2‐yloxy)acetamide, 6‐(substituted aryl)‐3‐[(pyrazin‐2‐yloxy)methyl][1,2,4]triazolo[3,4‐b][1,3,4]thiadiazole, and N‐[6‐({2‐[(pyrazin‐2‐yloxy)acetyl] hydrazino}sulfonyl)‐2‐methyl‐4‐oxo‐1,4‐dihydroquinazolin‐3(2H)yl]‐substituted aryl sulfonamides. The compounds were synthesized using the appropriate synthetic route. All synthesized compounds were assayed in vitro for antimycobacterial activity against the H37 Rv strain of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC) was determined for the test compounds as well as for the reference standards. The compound which exhibited good antimycobacterial activity contains the substituents fluorine and methoxy. These electron‐withdrawing or ‐donating substituents amend the lipophilicity of the test compounds which, in turn, alter the permeability across the bacterial cell membrane. Compounds 28 , 37 , and 43 showed good antimycobacterial activity while compound 51 showed a promising antimycobacterial activity.     

Synthesis and 3D‐QSAR Analysis of 2‐Chloroquinoline Derivatives as H37RV MTB Inhibitors

Frequency of tuberculosis is progressively increasing worldwide. New emerging strains of bacilli that are emerging are resistant to the currently available drugs which make this issue more alarming. In this regard, a series of substituted quinolinyl chalcones, quinolinyl pyrimidines, and pyridines were synthesized and evaluated for their antitubercular activity in vitro against Mycobacterium tuberculosis H₃₇RV. To establish the role of the 2‐chloroquinoline nucleus as a pharmacophoric group and study its influence on the antimycobacterial activity, a 3D‐QSAR study based on CoMFA and CoMSIA was undertaken on this set of 2‐chloroquinoline derivatives. Statistically significant models that are able to well correlate the antimycobacterial activity with the chemical structures of the 2‐chloroquinolines have been developed. The contour maps resulting from the best CoMFA and CoMSIA models were used to identify the structural features relevant to the biological activity in this series of analogs. Further analysis of these interaction‐field contour maps also showed a high level of internal consistency. The information obtained from the field 3‐D contour maps may be fruitfully utilized in the design of more potent 2‐chloroquinoline‐based analogs as potential antitubercular candidates.     

Synthesis and Antitubercular Activity of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium Chlorides

A series of 2‐(substituted phenyl/benzyl‐amino)‐6‐(4‐chlorophenyl)‐5‐(methoxycarbonyl)‐4‐methyl‐3,6‐dihydropyrimidin‐1‐ium chlorides 7–13 and 15 was synthesized in their hydrochloride salt form. The title compounds were characterized by FT‐IR, NMR (¹H and ¹³C) and elemental analysis. They were evaluated for their in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv, multidrug resistance tuberculosis and extensively drug resistance tuberculosis by agar diffusion method and tested for the cytotoxic action on peripheral blood mononuclear cells by MTT assay. Among all the tested compounds in the series, compounds 7 and 11 emerged as promising antitubercular agents at 16 μg/mL against multidrug resistance tuberculosis and over 64 μg/mL against extensively drug resistance tuberculosis. The conformational features and supramolecular assembly of the promising compounds 7 and 11 were determined by single crystal X‐ray study.     

An efficient and highly selective deprotection of N‐Fmoc‐α‐amino acid and lipophilic N‐Fmoc‐dipeptide methyl esters with aluminium trichloride and N,N‐dimethylaniline

Abstract: A novel procedure for the deprotection of the carboxyl group of amino acid methyl esters is presented. The process is carried out by the reagent system aluminium trichloride/N,N‐dimethylaniline that can successfully be applied to unblock the carboxyl moiety either of N‐Fmoc‐protected amino acid methyl esters and N‐Fmoc‐protected short dipeptide methyl esters. The chiralities of the optically pure amino acid or peptide precursors are maintained totally unchanged.     

N‐Benzylsalicylthioamides: Highly Active Potential Antituberculotics

A gseries of 29 new derivatives of N‐benzylsalicylthioamides was synthesized and the compounds were tested for in‐vitro antimycobacterial activity against Mycobacterium tuberculosis, Mycobacterium kansasii, and Mycobacterium avium. The activity was analyzed by quantitative structure‐activity relationship (QSAR). Activity increased with increasing lipophilicity and electron donating effect of the substituents in the acyl moiety and decreased with the electrophilic superdelocalizability of the molecules. The most active compounds are more active than isoniazid (INH) and are active against INH‐resistant potential pathogenic strains of mycobacterium.     

Synthesis and Biological Evaluation of Oxygen‐containing Heterocyclic Ring‐fused 23‐Hydroxybetulinic Acid Derivatives as Antitumor Agents

A collection of isoxazole and oxadiazole substituted 23‐hydroxybetulinic acid (HBA) derivatives were designed, synthesized and evaluated for their antitumor activity. Most of the newly synthesized compounds exhibited more potent antiproliferative activity than patent compound 23‐hydroxybetulinic acid, especially 13e and 14a were about four‐ to sevenfold more potent against all tested cancer cell lines than 23‐hydroxybetulinic acid. Furthermore, the in vivo antitumor activity of 13e and 14a was validated in H22 liver cancer and B16 melanoma xenograft mouse models. The structure–activity relationships of these 23‐hydroxybetulinic acid derivatives were also discussed based on the present investigation.     

6‐Hydrogen‐8‐Methylquinolones Active Against Replicating and Non‐replicating Mycobacterium tuberculosis

The screening of an in‐house quinolones library against Mycobacterium tuberculosis (Mtb) H₃₇Rv, followed by a first cycle of optimization, yielded 6‐hydrogen‐8‐methyl derivatives endowed with good potency. The antitubercular activity also encompassed the bacteria in a non‐replicating state (NRP‐TB) with minimum inhibitory concentration values lower than those of the reference agent, moxifloxacin. Among the best compounds, 11w and 11ai , characterized by a properly substituted piperidine at the C‐7 position, were active against single‐drug‐resistant (SDR‐TB) Mtb strains, maintaining overall good potency also against ciprofloxacin‐resistant Mtb. This study expands the body of SAR around antitubercular quinolones leading to reconsider the role played by the usual fluorine atom at the C‐6 position. Further elaboration of the 6‐hydrogen‐8‐methylquinolone scaffold, with a particular focus on the C‐7 position, is expected to give even more potent congeners holding promise for shortening the current anti‐TB regimen.     

Synthesis and Antimycobacterial Activity of Novel Thiadiazolylhydrazones of 1‐Substituted Indole‐3‐carboxaldehydes

A series of novel thiocarbohydrazones of substituted indoles and their corresponding thiadiazole derivatives were prepared, and their structures were confirmed by different analytical and spectroscopic methods. The derivatives were prepared by a sequential synthetic strategy including substitution at N‐1 position of indole ring by various aliphatic and benzylic substituents, followed by condensation with thiocarbohydrazide, and finally cyclization by triethyl orthoformate. The derivatives were tested for their antimycobacterial activity against Mycobacterium bovis BCG, and the results revealed that among the synthesized compounds, thiadiazole derivatives 4e , 4f , 4n , 4p , 4q , and 4t exhibited the highest activity with IC₅₀ value of 3.91 μg/mL. The results indicate that the thiadiazole moiety plays a vital role in exerting antimycobacterial activity.