Mahesh B. Palkar

Synthesis and pharmacological evaluation of a novel series of 5-(substituted) aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines as novel anti-inflammatory and analgesic agents

A novel series of 5-(substituted)aryl-3-(3-coumarinyl)-1-phenyl-2-pyrazolines (3a-l) were synthesized by reacting various substituted 3-aryl-1-(3-coumarinyl)propan-1-ones (2a-l) with phenylhydrazine in the presence of hot pyridine. Structures of all new synthesized compounds were characterized on the basis of elemental analysis and spectral data (IR, (1)H NMR and (13)C NMR). The title compounds were screened for in vivo anti-inflammatory and analgesic activities at a dose of 200 mg/kg b.w. Among the 12 prepared compounds, Compounds 3d, e, i and j exhibited significant anti-inflammatory activity in model of acute inflammation such as carrageenan-induced rat edema paw while compounds 3d and e showed considerable activity in model of chronic inflammation such as adjuvant-induced arthritis and were compared with diclofenac (13.5 mg/kg b.w.) as a standard drug. These compounds were also found to have significant analgesic activity in the acetic acid induced writhing model and antipyretic activity in yeast-induced pyrexia model along with minimum ulcerogenic index.

Synthesis and antibacterial activity of a novel series of 2,3-diaryl-substituted-imidazo(2,1-b)-benzothiazole derivatives.

Benzothiazole and imidazole compounds are extensively studied heterocyclics due to their wide spectrum of bioactivities. Among them, the imidazo(2,1‐b)‐benzothiazole derivatives are pharmacologically important because of their immunostimulant, anti‐inflammatory, antifungal, antimicrobial, antitumor, and other activities. In the present research work, a novel series of 2,3‐diaryl‐substituted imidazo(2,1‐b)‐benzothiazoles 13a–o have been synthesized by reaction of substituted 2‐aminobenzothiazoles 1–8 and an appropriately substituted α‐bromo‐1‐(4′′‐substituted)‐phenyl‐2‐(4′‐substituted)‐phenyl‐1‐ethanones 9–12 in the presence of anhydrous acetonitrile. They were characterized by physicochemical, elemental, and spectral (IR, 1H‐NMR, and Mass) data. All the synthesized compounds were screened for their in‐vitro antibacterial activity against Gram‐positive, Gram‐negative bacteria. The investigation of antibacterial screening data revealed that most of the compounds tested have demonstrated congruent activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa as compared with the standard ampicillin. Among the series, compounds 13d, 13h, and 13m exhibited excellent an antibacterial activity profile as compared with the standard. In summary, preliminary results indicate that some of the newly synthesized title compounds exhibited promising antibacterial activities and they warrant more consideration as prospective antimicrobials.

Synthesis and Antimycobacterial Activity of a Novel Series of Isonicotinylhydrazide Derivatives

A novel series of 14 new isonicotinyl hydrazide derivatives 2a–g, 3a–g containing a 4‐thiazolidinone / 2‐azetidinone nucleus were synthesized by reacting N′‐substituted arylidene / heteroarylidene isonicotinyl hydrazide 1a–g with thioglycollic acid in the presence of dry benzene and with chloroacetyl chloride in the presence of triethylamine, respectively. Structures of all newly synthesized compounds were characterized on the basis of elemental analyses and spectral data (IR and 1H‐NMR). All the title compounds were tested for their in‐vitro antimycobacterial activity against Mycobacterium tuberculosis H37Rv using Alamar‐Blue susceptibility test, and the activity is expressed as the minimum inhibitory concentration (MIC) in μg/mL. Among the series, compounds 2b, 2g, 3b, and 3g displayed an encouraging antimycobacterial activity profile as compared to that of the reference drugs isoniazid / rifampicin.

Synthesis and Antibacterial Activity of a New Series of 3-[3-(Substituted Phenyl)-1-Isonicotinoyl-1H-Pyrazol-5-yl]-2H-Chromen-2-one Derivatives

A novel series of 3‐[3‐(substituted phenyl)‐1‐isonicotinoyl‐1H‐pyrazol‐5‐yl]‐2H‐chromen‐2‐one derivatives 4a–k have been synthesized by the reaction of 3‐[2,3‐dibromo‐3‐(substituted phenyl) propanoyl]‐2H‐chromen‐2‐one 3a–k and isonicotinic acid hydrazide in the presence of triethylamine in absolute ethanol, characterized by spectral data and screened for their in‐vitro antibacterial activity against Gram‐positive and Gram‐negative bacteria. Among the series, compounds 4e, 4i, and 4k displayed an encouraging antibacterial activity profile as compared to the reference drug ampicillin against tested bacterial strains.

Design and synthesis of novel carbazolo–thiazoles as potential anti-mycobacterial agents using a molecular hybridization approach

Various substituted carbazolo–thiazoles (compounds 6a–6o) were synthesized in good yields using a molecular hybridization approach. The synthesized compounds were evaluated for their in vitro anti-tubercular activity against Mycobacterium tuberculosis H37Rv strain at the National Institute of Allergy and Infectious Diseases (Bethesda, MD, USA). Among the tested series, compound 6c (minimum inhibitory concentration 21 μM) showed the most promising anti-mycobacterial activity. Brief structure–activity relationship studies showed that the electron-donating groups (OCH3 and OH), particularly on the phenyl ring of the thiazole motif, had a positive correlation with the anti-mycobacterial activity. In addition, they displayed low cytotoxicity against a mammalian Vero cell line using the MTT assay, thereby having a high therapeutic index. This study shows the importance of molecular hybridization and the scope for the development of carbazole–thiazole compounds as potential anti-mycobacterial agents.

Synthesis of novel 4-nitropyrrole-based semicarbazide and thiosemicarbazide hybrids with antimicrobial and anti-tubercular activity.

We report the synthesis and screening of forty novel 4-nitropyrrole-semicarbazide conjugates inspired from the reported bio-potential of bromopyrrole alkaloids and semicarbazide derivatives for antimicrobial activity. Herein, hybrids 5k-5o, 5r, 5s and 5t displayed four-fold increased activity (MIC=0.39 μg/mL) against Escherichia coli compared to standard ciprofloxacin. Eight hybrids, 5k-5o and 5r-5t displayed equal antibacterial activity (MIC=1.56 μg/mL) against Klebsiella pneumonia compared to standard ciprofloxacin. Hybrid, 5k-5o (MIC=0.195 μg/mL) displayed highly potent antibacterial activity against MSSA as compared to standard ciprofloxacin. Eight-fold superior activity was observed for four hybrids 5k-5m and 5o (MIC=0.39 μg/mL) against MRSA. Further, nine hybrids displayed four-fold superior antifungal activity (MIC=0.78 μg/mL) compared to standard Amphotericin B. Encouraging MICs of these hybrids recognize them as promising leads for development of potential antimicrobial drugs.

Dehydrozingerone Inspired Styryl Hydrazine Thiazole Hybrids as Promising Class of Antimycobacterial Agents

Series of styryl hydrazine thiazole hybrids inspired from dehydrozingerone (DZG) scaffold were designed and synthesized by molecular hybridization approach. In vitro antimycobacterial activity of synthesized compounds was evaluated against Mycobacterium tuberculosis H37Rv strain. Among the series, compound 6o exhibited significant activity (MIC = 1.5 μM; IC50 = 0.48 μM) along with bactericidal (MBC = 12 μM) and intracellular antimycobacterial activities (IC50 = <0.098 μM). Furthermore, 6o displayed prominent antimycobacterial activity under hypoxic (MIC = 46 μM) and normal oxygen (MIC = 0.28 μM) conditions along with antimycobacterial efficiency against isoniazid (MIC = 3.2 μM for INH-R1; 1.5 μM for INH-R2) and rifampicin (MIC = 2.2 μM for RIF-R1; 6.3 μM for RIF-R2) resistant strains of Mtb. Presence of electron donating groups on the phenyl ring of thiazole moiety had positive correlation for biological activity, suggesting the importance of molecular hybridization approach for the development of newer DZG clubbed hydrazine thiazole hybrids as potential antimycobacterial agents.

Synthesis, pharmacological screening and in silico studies of new class of Diclofenac analogues as a promising anti-inflammatory agents.

A novel series of 5-[2-(2,6-dichlorophenylamino)benzyl]-3-(substituted)-1,3,4-oxadiazol-2(3H)-thione (4a-k) derivatives have been synthesized by the Mannich reaction of 5-[2-(2,6-dichlorophenylamino)benzyl]-1,3,4-oxadiazol-2(3H)-thione (3) with an appropriately substituted primary/secondary amines, in the presence of formaldehyde and absolute ethanol. Structures of these novel compounds were characterized on the basis of physicochemical, spectral and elemental analysis. The title compounds (4a-k) were screened for in vivo acute anti-inflammatory and analgesic activities at a dose of 10mg/kg b.w. Compound 4k exhibited the most promising and significant anti-inflammatory profile while compounds 4a, 4d, 4e, 4i, and 4j showed moderate to good inhibitory activity at 2nd and 4thh, respectively. These compounds were also found to have considerable analgesic activity (acetic acid induced writhing model) and antipyretic activity (yeast induced pyrexia model). In addition, the tested compounds were also found to possess less degree of ulcerogenic potential as compared to the standard NSAIDs. Compounds that displayed promising anti-inflammatory profile were further evaluated for their inhibitory activity against cyclooxygenase enzyme (COX-1/COX-2), by colorimetric COX (ovine) inhibitor screening assay method. The results revealed that the compounds 4a, 4e, 4g and 4k exhibited effective inhibition against COX-2. In an attempt to understand the ligand-protein interactions in terms of the binding affinity, docking studies were performed using Molegro Virtual Docker (MVD-2013, 6.0) for those compounds, which showed good anti-inflammatory activity. It was observed that the binding affinities calculated were in agreement with the IC50 values.

An appraisal on recent medicinal perspective of curcumin degradant: Dehydrozingerone (DZG).

Natural products serve as a key source for the design, discovery and development of potentially novel drug like candidates for life threatening diseases. Curcumin is one such medicinally important molecule reported for an array of biological activities. However, it has major drawbacks of very poor bioavailability and solubility. Alternatively, structural analogs and degradants of curcumin have been investigated, which have emerged as promising scaffolds with diverse biological activities. Dehydrozingerone (DZG) also known as feruloylmethane, is one such recognized degradant which is a half structural analog of curcumin. It exists as a natural phenolic compound obtained from rhizomes of Zingiber officinale, which has attracted much attention of medicinal chemists. DZG is known to have a broad range of biological activities like antioxidant, anticancer, anti-inflammatory, anti-depressant, anti-malarial, antifungal, anti-platelet and many others. DZG has also been studied in resolving issues pertaining to curcumin since it shares many structural similarities with curcumin. Considering this, in the present review we have put forward an effort to revise and systematically discuss the research involving DZG with its biological diversity. From literature, it is quite clear that DZG and its structural analogs have exhibited significant potential in facilitating design and development of novel medicinally active lead compounds with improved metabolic and pharmacokinetic profiles.

Synthesis and Evaluation of Anti-inflammatory and Analgesic Activities of a Novel Series of Coumarin Mannich Bases

A novel series of coumarinyl Mannich bases (3a-1) have been synthesized by reacting 3-acetyl coumarin (1) with various substituted secondary amines (2a-1) in presence of paraformaldehyde. The structures of the newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR and HRMS (high resolution mass spectral) data. Title compounds were screened for in vivo acute anti-inflammatory activity using the carrageenan-induced rat paw edema assay model. Among the compounds tested, 3-[3-(diethylamino)propanoyl]-2H-chromen-2-one (3a)and 3-[3-(piperidine-1-yl) propanoyl]-2H-chromen-2-one (3c) showed 63.1 and 66.7% inhibition, respectively, as compared to the standard drug diclofenac (CAS 15307-86-5, 68.8%). These potent compounds showed encouraging analgesic andantipyretic activities.