Girish A. Hampannavar

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.

A Recent Perspective on Discovery and Development of Diverse Therapeutic Agents Inspired from Isatin Alkaloids

Isatin as an alkaloidal framework have consistently attracted attention of medicinal chemist towards development of wide range of novel therapeutic agents. This review report has discussed significant isatin lead molecules and their derivatives which have shown promising biological potential in recent times. The substituted isatins showing a potent pharmacological activities such as antimicrobial, antitubercular, anticancer, antioxidant, anti-histaminic, anti-HIV, antiviral, anti-inflammatory, anti-Parkinsons and antidiabetic have been described in this review. The mechanism of action leading to therapeutic activity of the respective isatin derivation has also been recorded. This review reveals that the systematic and rational modifications on isatin motif exhibited significant bio-activities which can be exploited for the development of potent novel therapeutic agents in the future studies. Hence the quest to investigate more structural alterations on isatin scaffold should be continued.

An insight on synthetic and medicinal aspects of pyrazolo[1,5-a]pyrimidine scaffold.

Pyrazolo[1,5-a]pyrimidine scaffold is one of the privileged hetrocycles in drug discovery. Its application as a buliding block for developing drug-like candidates has displayed broad range of medicinal properties such as anticancer, CNS agents, anti-infectious, anti-inflammatory, CRF1 antagonists and radio diagnostics. The structure-activity relationship (SAR) studies have acquired greater attention amid medicinal chemists, and many of the lead compounds were derived for various disease targets. However, there is plenty of room for the medicinal chemists to further exploit this privileged scaffold in developing potential drug candidates. The present review briefly outlines relevant synthetic strategies employed for pyrazolo[1,5-a]pyrimidine derivatives. It also extensively reveals significant biological properties along with SAR studies. To the best of our understanding current review is the first attempt made towards the compilation of significant advances made on pyrazolo[1,5-a]pyrimidines reported since 1980s.

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.

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.

Ligand and structure based in silico studies to identify kinesin spindle protein (KSP) inhibitors as potential anticancer agents

Kinesin spindle protein (KSP) belongs to the kinesin superfamily of microtubule-based motor proteins. KSP is responsible for the establishment of the bipolar mitotic spindle which mediates cell division. Inhibition of KSP expedites the blockade of the normal cell cycle during mitosis through the generation of monoastral MT arrays that finally cause apoptotic cell death. As KSP is highly expressed in proliferating/cancer cells, it has gained considerable attention as a potential drug target for cancer chemotherapy. Therefore, this study envisaged to design novel KSP inhibitors by employing computational techniques/tools such as pharmacophore modelling, virtual database screening, molecular docking and molecular dynamics. Initially, the pharmacophore models were generated from the data-set of highly potent KSP inhibitors and the pharmacophore models were validated against in house test set ligands. The validated pharmacophore model was then taken for database screening (Maybridge and ChemBridge) to yield hits, which were further filtered for their drug-likeliness. The potential hits retrieved from virtual database screening were docked using CDOCKER to identify the ligand binding landscape. The top-ranked hits obtained from molecular docking were progressed to molecular dynamics (AMBER) simulations to deduce the ligand binding affinity. This study identified MB-41570 and CB-10358 as potential hits and evaluated these experimentally using in vitro KSP ATPase inhibition assays.

An appraisal on synthetic and pharmaceutical perspectives of pyrazolo[4,3-d]pyrimidine scaffold

Pyrazolo[4,3-d]pyrimidine, a fused heterocycle bearing pyrazole and pyrimidine portions has gained a significant attention in the field of bioorganic and medicinal chemistry. Pyrazolo[4,3-d]pyrimidine derivatives have demonstrated numerous pharmacological activities particularly, anti-cancer, anti-infectious, phosphodiesterase inhibitors, adenosine antagonists and cytokinin antagonists etc. This review extensively unveils the synthetic and pharmacological diversity with special emphasis on structural variations around pyrazolo[4,3-d]pyrimidine scaffold. This endeavour has thus uncovered the medicinal worthiness of pyrazolo[4,3-d]pyrimidine framework. To the best of our knowledge this review is the first compilation on synthetic, medicinal and structure activity relationship (SAR) aspects of pyrazolo[4,3-d]pyrimidines since 1956.

Design, synthesis and QSAR studies of 2-amino benzo[d]thiazolyl substituted pyrazol-5-ones: novel class of promising antibacterial agents

Novel analogs of 3-(4-substituted benzylideneamino)-N-(6-substituted-1,3-benzo[d]thiazol-2-yl)-4,5-dihydro-5-oxo-pyrazole-1-carboxamide (5a–s) were designed and synthesized by reacting 3-amino-N-(6-substituted-1,3-benzo[d]thiazol-2-yl)-4,5-dihydro-5-oxo-pyrazole-1-carboxamide (4a–d) with p-substituted benzaldehydes. The Infrared Spectroscopy, 1H-Nuclear Magnetic Resonance, 13C-Nuclear Magnetic Resonance, and High Resolution Mass Spectra spectral data confirmed the structures of all the novel synthesized compounds. Among the series tested, two compounds 5k and 5o displayed promising antibacterial activity especially against Staphylococcus aureus (MIC = 3.14 and 1.57 µg/mL) and Bacillus subtilis (MIC = 3.12 and 1.84 µg/mL) respectively. Further, these title compounds were also assessed for their cytotoxic activity (IC50) against mammalian Vero cell line using 3-(4,5-dimethylthiazo-2-yl)-2,5-diphenyl-tetrazolium bromide assay, indicating that the compounds exhibit antibacterial activity at non-cytotoxic concentrations. Field based three-dimensional quantitative structure–activity relationships were also discussed based on the antimicrobial screening data.Graphical AbstractSynthesis, spectral studies, antibacterial evaluation and QSAR studies of nineteen novel Schiff bases of pyrazol-5-one derivatives derived from 2-aminobenzothiazole nucleus are described.

Novel synthetic organic compounds inspired from antifeedant marine alkaloids as potent bacterial biofilm inhibitors.

In this paper, we have reported seventeen novel synthetic organic compounds derived from marine bromopyrrole alkaloids, exhibiting potential inhibition of biofilm produced by Gram-positive bacteria. Compound 5f with minimumbiofilm inhibitory concentration(MBIC) of 0.39, 0.78 and 3.125 μg/mL against MSSA, MRSA and SE respectively, emerged as promising anti-biofilm lead compounds. In addition, compounds 5b, 5c, 5d, 5e, 5f, 5h, 5i and 5j revealed equal potency as that of the standard drug Vancomycin (MBIC = 3.125 μg/mL) against Streptococcus epidermidis. Notably, most of the synthesized compounds displayed better potency than Vancomycin indicating their potential as inhibitors of bacterial biofilm. The cell viability assay for the most active hybrid confirms its anti-virulence properties which need to be further researched.