Harish Rajak

Synthesis of Novel 2,5‐Disubstituted 1,3,4‐Thiadiazoles for Their Potential Anticonvulsant Activity: Pharmacophoric Model Studies

A series of novel N1‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N4‐(4‐substituted benzaldehyde)‐semicarbazone 1–12, N1‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N4‐[1‐(4‐substituted phenyl)ethanone]‐semicarbazone 13‐16, and N1‐[5‐(4‐substituted phenyl)‐1,3,4‐thiadiazol‐2‐yl]‐N4‐[1‐(4‐substituted phenyl) (phenyl) methanone]‐semicarbazone 17–20 were synthesized for their anticonvulsant activity. The chemical structures of the compounds were proved by elemental and spectral (IR, 1H‐NMR, 13C‐NMR, and MS) analysis. The anticonvulsant potential of the compounds was investigated using maximal electroshock seizure (MES) and subcutaneous pentylenetrtrazole (scPTZ) models. Compound 19 was found to possess significant anticonvulsant activity in both the models employed for anticonvulsant evaluation. Compounds 8, 13, 15, and 16 also demonstrated a marked anticonvulsant property. The results of the present study validated that the pharmacophore model with four binding sites is essential for anticonvulsant activity. The efforts were also made to establish structure‐activity relationships among the synthesized compounds.

2,5-Disubstituted-1,3,4-oxadiazoles/thiadiazole as surface recognition moiety: Design and synthesis of novel hydroxamic acid based histone deacetylase inhibitors

The enzymatic inhibition of histone deacetylase activity has come out as a novel and effectual means for the treatment of cancer. Two novel series of 2-[5-(4-substitutedphenyl)-[1,3,4]-oxadiazol/thiadiazol-2-ylamino]-pyrimidine-5-carboxylic acid (tetrahydro-pyran-2-yloxy)-amides were designed and synthesized as novel hydroxamic acid based histone deacetylase inhibitors. The antiproliferative activities of the compounds were investigated in vitro using histone deacetylase inhibitory assay and MTT assay. The synthesized compounds were also tested for antitumor activity against Ehrlich ascites carcinoma cells in Swiss albino mice. The efforts were also made to establish structure-activity relationships among synthesized compounds. The results of the present studying indicates 2,5-disubstituted 1,3,4-oxadiazole/thiadiazole as promising surface recognition moiety for development of newer hydroxamic acid based histone deacetylase inhibitor.

Design of Combretastatin A-4 Analogs as Tubulin Targeted Vascular Disrupting Agent with Special Emphasis on Their Cis-Restricted Isomers

Tubulin protein is a highly imperative and feasible goal for anticancer drug discovery. Hundreds of naturally occurring, semi synthetic and synthetic antitubulin agents have been reported till now. Among these, Combretastatin A - 4 (CA - 4) is effective antimitotic agent possessing potent cytotoxicity against a panel of cancer cells, including multi-drug resistant cancer cell lines. The inadequate water solubility and inactivation of these analogs during storage limit their use as clinical anticancer agents. To overcome these shortcomings, numerous water soluble amino analogs, amino acid derivative, phosphate prodrug (CA - 4P) and cis-locked CA - 4 have been developed with distinctive attributes of antitubulin and antivascular properties in a wide variety of preclinical tumor models. Subsequently, several heterocycle based cis restricted CA - 4 analogs are being reported for antitumor activity against collection of cancer cell lines. This review recapitulates the rational design, structure activity relationship, pharmacokinetic and pharmacodynamic profile of synthesized cis restricted CA - 4 analogs.

Medicinal significance of benzothiazole scaffold: an insight view

Heterocycles bearing nitrogen, sulphur and thiazole moieties constitute the core structure of a number of biologically interesting compounds. Benzothiazole, a group of xenobiotic compounds containing a benzene ring fused with a thiazole ring, are used worldwide for a variety of therapeutic applications. Benzothiazole and their heterocyclic derivatives represent an important class of compounds possessing a wide spectrum of biological activities. The myriad spectrum of medicinal properties associated with benzothiazole related drugs has encouraged the medicinal chemists to synthesize a large number of novel therapeutic agents. Several analogues containing benzothiazole ring system exhibit significant antitumour, antimicrobial, antidiabetic, anti-inflammatory, anticonvulsant, antiviral, antioxidant, antitubercular, antimalarial, antiasthmatic, anthelmintic, photosensitizing, diuretic, analgesic and other activities. This article is an attempt to present the research work reported in recent scientific literature on different pharmacological activities of benzothiazole compounds.

Novel semicarbazones based 2,5-disubstituted-1,3,4-oxadiazoles: One more step towards establishing four binding site pharmacophoric model hypothesis for anticonvulsant activity

A series of novel N(1)-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N(4)-(4-substitutedbenzaldehyde)-semicarbazone, N(1)-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N(4)-[1-(4-substitutedphenyl)ethanone]-semicarbazone and N(1)-{5-[(naphthalene-2-yloxy)methyl]-1,3,4-oxadiazol-2-yl}-N(4)-[1-(4-substitutedphenyl) (phenyl) methanone]-semicarbazone were designed and synthesized on the basis of semicarbazone based pharmacophoric model to meet the structural requirements necessary for anticonvulsant activity. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure (MES), subcutaneous pentylenetrtrazole (scPTZ) and subcutaneous strychnine (scSTY) models. Some of the selected active compounds were subjected to GABA assay to confirm their mode of action. The efforts were also made to establish structure activity relationships among synthesized compounds. The results of the present studying validated that the pharmacophoric model with four binding sites is essential for anticonvulsant activity.

Novel limonene and citral based 2,5-disubstituted-1,3,4-oxadiazoles: A natural product coupled approach to semicarbazones for antiepileptic activity

Two novel series of N(4)-(5-(2/3/4-substituted-phenyl)-1,3,4-oxadiazol-2-yl)-N(1)-(2-methyl-5-(prop-1-en-2-yl)cyclohex-2-enylidene)semicarbazide and N(4)-(5-(2/3/4-substituted-phenyl)-1,3,4-oxadiazol-2-yl)-N(1)-(3,7-dimethylocta-3,6-dienylidene)-semicarbazide were synthesized to meet structural prerequisite indispensable for anticonvulsant activity. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure (MES), subcutaneous pentylenetrtrazole (scPTZ) and subcutaneous strychnine (scSTY) models. The rotorod test was conducted to evaluate neurotoxicity. Some of the selected active compounds were subjected to GABA assay to confirm their mode of action. The outcome of the present investigations proved that the four binding sites pharmacophore model is vital for anticonvulsant activity. The efforts were also made to establish structure-activity relationships among test compounds.

Synthesis and biological evaluation of novel benzothiazole clubbed fluoroquinolone derivatives.

In the present investigation, synthesis and anti-bacterial, analgesic and anthelmintic evaluation of a novel series of fluoroquinolone derivatives clubbed with benzothiazole moeity has been described. The synthesized compounds were characterised by spectral analysis (IR and 1H NMR). Preliminary results indicated that the most of the synthesized compounds demonstrated good activities against gram negative and gram positive bacterial strains. Compounds 5a, 5b, 5f and 5k demonstrated potent anti-bacterial activities. Compound 5a exhibited most potent anti-bacterial activity with MIC values of 04, 03, 08 and 15 µg/ mL against B. subtilis, S. aureus, E. coli and P. aeruginosa. Analogs 5a, 5c, 5g and 5h showed promising anthelmintic activity against Eisemia foetida in a low concentration as compared to standard drug piperazine citrate with mean paralysis time ranging 22.60 ± 2.46 to 31.60 ± 3.07 min. All synthesized compounds depicted good in vivo analgesic activity with compound 5a exhibiting the most potent activity of 55.19% inhibition of writhing in comparison to the standard drug.

Design, synthesis, and evaluation of thiazolidinone derivatives as antimicrobial and anti-viral agents.

A series of 1,3‐thiazolidin‐4‐one derivatives were prepared by the reaction of respective aromatic amine, aromatic aldehyde, and thioglycolic acid in dry benzene/toluene. The newly synthesized compounds were characterized on the basis of elemental analysis, IR, 1HNMR, and mass spectra. The newly synthesized final compounds were evaluated for their in vitro antibacterial, antifungal, and anti‐viral activities. Preliminary results indicated that some of the compounds demonstrated antibacterial activity in the range of 7–13 μg/mL, antifungal activity in the range of 13–17 μg/mL, comparable with the standard drugs, ciprofloxacin and fluconazole. Structure–activity relationship studies revealed that the nature of the substituents at the 2 and 3 positions of the thiazolidinone nucleus had a significant impact on the in vitro antimicrobial and anti‐viral activity of these classes of agents.

Ebola virus disease: past, present and future

Ebola virus disease is one of the most deadly ailments known to mankind due to its high mortality rate (up to 90%) accompanying with the disease. Ebola haemorrhagic fever (EHF) is an infectious disease of animal that can be transmitted to both human and non-human primates. The first epidemic of EHF occurred in 1976 in the Democratic Republic of the Congo. The incubation period of ebola is less than 21 days. Ebola virus infections are depicted by immune suppression and a systemic inflammatory response that leads to damage of the vascular, coagulation and immune systems, causing multi-organ failure and shock. Five genetically distinct members of the Filoviridae family responsible for EHF are as follows: Zaire ebolavirus, Sudan ebolavirus, Cote d’Ivoire ebolavirus, Bundibugyo ebolavirus and Reston ebolavirus. The ongoing 2014 West Africa ebola epidemic has been considered as the most serious panic in the medical field with respect to both the number of human cases and death toll. The natural host for ebola virus is unknown, thus it is not possible to carry out programs to regulate or abolish virus from transmission to people. The ebola virus infection provides little chance to develop acquired immunity causing rapid progression of the disease. It is pertinent to mention that at present, there is no antiviral therapy or vaccine that is helpful against ebola virus infection in humans. The impediment of EHF necessitates much better understanding of the epidemiology of the disease, particularly the role of wildlife, as well as bats, in the spread of ebola virus to humans.

A novel series of 2,5-disubstituted 1,3,4-oxadiazoles: synthesis and SAR study for their anticonvulsant activity.

In search for a better anticonvulsant drug and the importance of semicarbazones and 2,5‐disubstituted 1,3,4‐oxadiazoles as anticonvulsant pharmacophore, a series of novel substituted semicarbazones were designed, synthesized, and evaluated for their anticonvulsant activity. The chemical structures of the synthesized molecules were confirmed by elemental and spectral (IR, 1H NMR, 13C NMR and MS) analysis. The anticonvulsant activities of the compounds were investigated using maximal electroshock seizure and subcutaneous pentylenetetrazole (scPTZ) models. Efforts were also made to establish structure–activity relationships among synthesized compounds. The results of the present study validated that the pharmacophore model with four binding sites is essential for anticonvulsant activity.