Rahul V. Patel

Synthesis of benzimidazolyl-1,3,4-oxadiazol-2ylthio-N-phenyl (benzothiazolyl) acetamides as antibacterial, antifungal and antituberculosis agents

To affiliate multiple bioactivities in a compact heteronuclei, two series of benzimidazole based 1,3,4-oxadiazoles were synthesized and assessed in vitro for their efficacy as antimicrobial agents against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Shigella flexneri), four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus clavatus, Candida albicans) and Mycobacterium tuberculosis H37Rv and best results were observed amongst the N-benzothiazolyl aetamide series. The lipophilicity (LogP) influence on the biological profile (MICs) of the prepared products was also discussed. Upon biological screening, it was observed that the majority of the compounds were found to possess a significant broad spectrum antimicrobial (3.12-25 μg/mL of MIC) and antitubercular (6.25-25 μg/mL of MIC) potential. The structural assignments of the new products were done on the basis of IR, (1)H NMR, (13)C NMR spectroscopy and elemental analysis.

Synthesis and studies of novel 2-(4-cyano-3-trifluoromethylphenyl amino)-4-(quinoline-4-yloxy)-6-(piperazinyl/piperidinyl)-s-triazines as potential antimicrobial, antimycobacterial and anticancer agents

A series of novel s-triazine analogs were synthesized and characterized by IR, (1)H NMR, (13)C NMR, (19)F NMR spectroscopy and elemental analysis. Preliminary screening of target compounds against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Shigella flexneria), four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus clavatus, Candida albicans) and Mycobacterium tuberculosis H37Rv indicated that 5d, 5h, 5n, 5p, 5q, 5r, 5s, 5t and 5u were the most active compounds among twenty one studied. Thus, they were further subjected to in vitro biological evaluation against human prostate cancer cell line (DU-145) and the results indicate that two compounds 5n and 5s were markedly active.

Antimicrobial, anti-TB, anticancer and anti-HIV evaluation of new s-triazine-based heterocycles.

BACKGROUND The acquirement of resistance by microorganisms to the antimicrobial arsenal is a threat to public health. A recent WHO report estimated that 1.3 million HIV-negative people and 0.38 million HIV-positive people died from TB in 2009. Various forms of cancer account for a high percentage of deaths in both women (breast cancer) and men (prostate cancer). RESULTS & DISCUSSION In vitro activity assessment of newly constructed s-triazines against a panel of microorganisms including bacteria, fungi and Mycobacteria demonstrated that the compounds are of immense attraction for impending drug discovery. They were further examined for in vitro activity against breast cancer and prostate cancer cell lines, as well as HIV-1 (III(B)) and HIV-2 (ROD) viral strains. Proposed structural confirmation studies by IR, (1)H NMR, (13)C NMR, (19)F NMR spectroscopy and elemental analysis were in accordance. CONCLUSION Activity profiles of the products may contribute considerably to future drug-discovery studies.

In vitro antimicrobial assessment of coumarin-based s -triazinyl piperazines

A series of 1,3,5-triazine derivatives that contain aniline, coumarins (4-hydroxy coumarin and 7-hydroxy-4-methyl coumarin) and different piperazine moieties as substituent on the carbon atoms of the triazine ring have been synthesized by a simple and efficient synthetic protocol. Comparative studies were performed on above series, which were synthesized with conventional and microwave heating methods. The microwave method was observed to be more beneficial as it provides an increase in yield and 90–95% reduction time. All the synthesized compounds were then examined for their efficacy against two Gram −ve bacteria (Escherichia coli and Pseudomonas aeruginosa), two Gram +ve bacteria (Staphylococcus aureus and Bacillus subtilis) and two fungal species (Candida albicans and Aspergillus niger) with an intent to overcome multiple drug resistance to the pathogenic strains. All the synthesized compounds were structurally elucidated by IR, 1H NMR, 13C NMR and elemental analysis.

A new class of 2-(4-cyanophenyl amino)-4-(6-bromo-4-quinolinyloxy)-6-piperazinyl (piperidinyl)-1,3,5-triazine analogues with antimicrobial/antimycobacterial activity.

This study presents the synthesis and in vitro pharmacological evaluations of novel 2-(4-cyanophenyl amino)-4-(6-bromo-4-quinolinyloxy)-6-piperazinyl (piperidinyl)-1,3,5-triazines. The title compounds were assayed for their in vitro antimicrobial activity against eight bacteria (Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella typhi, Proteus vulgaris, Shigella flexneria) and four fungi (Aspergillus niger, Aspergillus fumigatus, Aspergillus clavatus, Candida albicans) using paper disc diffusion and agar streak dilution method as well as against Mycobacterium tuberculosis H37Rv strain using BACTEC MGIT and Lowenstein-Jensen MIC method. The bioassay results indicate that nine compounds namely 5d, 5h, 5n, 5p, 5q, 5r, 5s, 5t and 5u could be considered as possible potential agents with dual antimicrobial and antimycobacterial activities. The structures of the compounds were elucidated with the aid of IR, 1H NMR, 13C NMR, 19F NMR spectroscopy and CHN analysis.

Medicinal Chemistry Discoveries among 1,3,5-Triazines: Recent Advances (2000-2013) as Antimicrobial, Anti-TB, Anti-HIV and Antimalarials

The chemistry and an extensive spectrum of biological activities of s-triazines have been examined since several decades and this heterocyclic core has received emerging consensus. This article aims to summarize recent advances (2000-2013) made towards the discovery of antimicrobial, antituberculosis, anti-HIV and antimalarial agents holding 1,3,5-triazine ring as a nucleus with the substitution of several types of nucleophiles. Molecular patterns associated with particular potency have been identified targeting several Gram-positive and Gram-negative bacteria and some fungal species, mycobacterium tuberculosis H37Rv, HIV type I and HIV type II, particularly, HIV-1I IIB and HIV- 1ROD strains as well as a variety of P. falciparum malarial strains as chloroquine-resistant K1, chloroquine-susceptible NF54, chloroquine-sensitive 3D7, P. falciparum (D6 clone), P. falciparum (W2 clone), cycloguanil-resistant FCR-3, chloroquine sensitive RKL2. The report will be of considerable interest to gain useful information for the furtherance of drug discovery with extended 1,3,5-triazine designs.

Piperazine derivatives for therapeutic use: a patent review (2010-present)

ABSTRACT Introduction: Piperazine, a six membered nitrogen containing heterocycle, is of great significance to the rational design of drugs. This moiety can be found in a plethora of well-known drugs with various therapeutic uses, such as antipsychotic, antihistamine, antianginal, antidepressant, anticancer, antiviral, cardio protectors, anti-inflammatory, and imaging agents. Slight modification to the substitution pattern on the piperazine nucleus facilitates a recognizable difference in the medicinal potential of the resultant molecules. Areas covered: Scifinder was the main source used to search for patents containing piperazine compounds with therapeutic uses. The article describes a variety of molecular designs bearing piperazine entity furnishing CNS agents, anticancer, cardio-protective agents, antiviral, anti-tuberculosis, anti-inflammatory, antidiabetic, and antihistamine profiles, as well as agents relieving pain and useful in imaging applications. Expert opinion: The great interest gathered to explore piperazine based molecules in relatively few years reflects the broad potential of the entity. Earlier, this scaffold was considered to express CNS activity only. However, a significant increase in research covering studies of several different activities of piperazine ring suggest a successful emergence of the pharmacophore. Certain patents outlined in the present article recommend that piperazines can be a flexible building block to discover drug-like elements and modification of substituents present on the piperazine ring may have a significant impact on the pharmacokinetic and pharmacodynamics factors of the resulting molecules. This article aims to provide insights to piperazine based molecular fragments that would assist drug discoverers to rationally design molecules for various diseases. We anticipate, and highly recommend, further therapeutic investigations on this motif.

Chrysin-benzothiazole conjugates as antioxidant and anticancer agents.

7-(4-Bromobutoxy)-5-hydroxy-2-phenyl-4H-chromen-4-one, obtained from chrysin with 1,4-dibromobutane, was combined with a wide range of 6-substituted 2-aminobenzthiazoles, which had been prepared from the corresponding anilines with potassium thiocyanate. Free radical scavenging efficacies of newer analogues were measured using DPPH and ABTS assays, in addition to the assessment of their anticancer activity against cervical cancer cell lines (HeLa and CaSki) and ovarian cancer cell line (SK-OV-3) implementing the SRB assay. Cytotoxicity of titled compounds was checked using Madin-Darby canine kidney (MDCK) non-cancer cell line. Overall, 6a-r indicated remarkable antioxidant power as DPPH and ABTS(+) scavengers; particularly the presence of halogen(s) (6g, 6h, 6j-6l) was favourable with IC50 values comparable to the control ascorbic acid. Unsubstituted benzothiazole ring favored the activity of resultant compounds (6a and 6r) against HeLa cell line, whereas presence of chlorine (6g) or a di-fluoro group (6k) was a key to exert strong action against CaSki. Moreover, a mono-fluoro (6j) and a ketonic functionality (6o) were beneficial to display anticipated anticancer effects against ovarian cancer cell line SK-OV-3. The structural assignments of the new products were done on the basis of IR, (1)H NMR, (13)C NMR spectroscopy and elemental analysis.

Synthesis of novel 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one condensed s-triazinyl piperazines and piperidines as antimicrobial agents

Synthesis and antimicrobial activity of a new series of 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-ones based on various substituted piperazines and piperidines incorporating a 1,3,5-triazine moiety are reported in this article. 3-{5-[(4,6-dichloro-1,3,5-triazin-2-yl)sulfanyl]-1,3,4-oxadiazol-2-yl}-2H-chromen-2-one 3 was obtained by the reaction of 2,4,6-trichloro-1,3,5-triazine 1 with 3-(5-sulfanyl-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one 2 which was obtained by following the method reported in the literature. Intermediate 3 was then condensed with 8-hydroxyquinoline 4 to form 3-(5-{[4-chloro-6-(quinolin-4-yloxy)-1,3,5-triazin-2-yl]sulfanyl}-1,3,4-oxadiazol-2-yl)-2H-chromen-2-one 5. This was further treated with various substituted piperazines and piperidines to obtain the title compounds 7a–u, which were then subjected to determine their in vitro biological efficacy against bacterial and fungal strains as two Gram-positive bacteria (S. aureus, B. cereus), six Gram-negative bacteria (E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, and S. flexneria) and two fungal species (A. niger, and C. albicans) with an intent to develop novel class of antimicrobial agents. The results indicate that some of the novel s-triazines have noteworthy activity in MIC (μg/ml) and zone of inhibition (mm) indicating potential leads for further drug discovery study. All the final compounds were structurally elucidated on the basis of IR, 1H NMR, 13C NMR, 19F NMR spectroscopy, and elemental analysis.

New Quinolinyl–1,3,4–Oxadiazoles: Synthesis, In Vitro Antibacterial, Antifungal and Antituberculosis Studies

In order to generate hybrid antimicrobial remedies with novel mode of action, two series of quinoline based 1,3,4-oxadiazole derivatives condensed with N-aryl/benzothiazolyl acetamides were synthesized and the MIC values of the compounds towards eight reference bacterial strains (S. aureus, B. cereus, E. coli, P. aeruginosa, K. pneumoniae, S. typhi, P. vulgaris, S. flexneri), four fungi (A. niger, A. fumigatus, A. clavatus, C. albicans) and Mycobacterium tuberculosis H37Rv were assayed in vitro. Quinoline-6-carboxlic acid was treated with thionyl chloride in refluxing methanol to obtain the corresponding ester derivative to be hydrazinolyzed by 99% hydrazine hydrate in ethanol to produce carbohydrazide intermediate. The carbohydrazide precursor underwent cyclization by carbon disulfide and ethanolic KOH to construct 5-quinolinyl-6-yl-1,3,4-oxadiazol-2-thiol. Substituted 2-chloro-N-phenyl(benzothiazolyl)aceta-mide derivatives were then condensed to 1,3,4-oxadiazole nucleus via sulphur linkage to yield the desired products. Target products bearing N-benzothiazolyl-2-chloroacetamides displayed good inhibitory potential. The biological screening identified that many final analogues exhibited a significant inhibition of the growth of microorganisms at 3.12-25 μg/mL of MIC, which were comparable to control drugs. The influence of the presence of various functional groups to the phenyl/benzothiazolyl ring on activity profiles was investigated. The proposed structures of the newly prepared products were confirmed with the aid of IR, 1H NMR, 13C NMR spectroscopy and elemental analysis. These results may provide new insights in the design of a novel pool of bioactive templates.