Microwave-assisted synthesis,molecular docking and antitubercular activity of 1,2,3,4-tetrahydropyrimidine-5-carbonitrile derivatives

Based on bioisosteric similarities with isoniazid, a series of 1,2,3,4-tetrahydropyrimidine-5-carbonitrile derivatives has been designed. The target compounds have been synthesized by multicomponent reaction which involves one-pot organic reactions using ethylcyanoacetate, urea/thiourea and arylaldehydes in presence of ethanolic K₂CO₃. Two methodologies, conventional and microwave-assisted, have been adopted for the synthesis. The later strategy gave high yields in less than 10 min as compared to long hours using the former approach. Molecular docking of the target compounds into the enzyme Mycobacterium tuberculosis enoyl reductase (InhA) revealed important structural information on the plausible binding interactions. Major binding interactions were found to be of dispersion type (residues Tyr158, Ile215, Met103 and Met199) and a hydrogen bond with Tyr158. Binding poses of the all the compounds were energetically favorable and showed good interactions with the active site residues. Few selected compounds were also evaluated for antitubercular activity in vitro against drug-sensitive M. tuberculosis H37Rv strain and clinically isolated S, H, R and E resistant M. tuberculosis by luciferase reporter phage (LRP) assay method. Some compounds displayed promising antimycobacterial activity comparable or less than the standard drugs isoniazid and rifampicin.     

Cell-mediated resistance induced by axenic amoebal RNA--protein fraction

Immunologically potent, RNA protein fraction could be isolated from axenic Entamoeba histolytica (NIH: 200) using a phenol extraction method. Immunization of animals with amoebal RNA protein (Eh RNA) fraction evoked an intense cellular sensitization. In immunized animals the percent leucocyte migration inhibition was found to be 73.7 +/- 6.9. In control groups where the animals were treated with Freund's complete adjuvant, yeast RNA and amoebal RNA treated with RNase, the percent leucocyte migration inhibition was 15.8 +/- 2.9, 16.8 +/- 6.2 and 14.0 +/- 4.0 respectively. Anti Eh RNA antibodies (haemagglutinins and precipitins) could not be demonstrated in immunized animals at any stage of observations. The cellular immunity could be maintained at its high level by giving three immunization doses of Eh RNA and also a high degree (95.45%) of protection against experimental challenge with virulent strain of E. histolytica could be obtained in immunized animals. The immunogenic and protective capabilities of Eh RNA were found to be specific since they were abolished by the RNase treatment. Further, the yeast RNA failed to elicit immunity.     

Anti-inflammatory activity of piperine

Piperine (1-peperoyl piperidine) was isolated from Piper nigrum Linn for the evaluation of anti-inflammatory activity in rats. Different acute and chronic experimental models like carrageenin-induced rat paw edema, cotton pellet granuloma, and croton oil-induced granuloma pouch, were employed. Simultaneously, biochemical estimations were made to elucidate the underlying mechanism of the action. Piperine acted significantly on early acute changes in inflammatory processes and chronic granulative changes. It also acted partially through stimulation of pituitary adrenal axis. Exudative changes in both acute and chronic models, however, were insignificant.     

alpha-Santonin 1,2-reductase and its role in the formation of dihydrosantonin and lumisantonin by Pseudomonas cichorii S

1,2-Dihydrosantonin is the first stable product in the degradative pathway of alpha-santonin by Pseudomonas cichorii S. Its formation is catalyzed by an oxidoreductase, which is NADH or NADPH dependent and has an apparent Km value of 66.66 microM for santonin and 44.33 microM for NADH. The enzyme activity is stable at pH 6.0, 7.0, and 8.0, and is not affected by EDTA and divalent metal ions. It is postulated that the enzymic reduction of santonin occurs via formation of a transient zwitterionic intermediate, which undergoes nonenzymatic 1,4-sigmatropic rearrangement to yield lumisantonin during the solvent extraction process. Lumisantonin is, thus, not a true metabolic intermediate but an artifact.     

Mitochondrial Complex I Impairment and Nitrate Reductase Activity in Leaves of Nicotiana sylvestris

Loss of major mitochondrial complex I subunit Nad 7 in the leaves of CMS II mutant of Nicotiana sylvestris caused increase in both in vivo and in vitro nitrate reductase activities and the per cent activation state of NR was also higher in CMS II as against wild type. The differences suggest a possibility for export of mitochondrial NADH due to impairment of complex I, a major and high affinity sink for NADH. Loss of complex I subunit also resulted in constitutive expression of alternate oxidase (Aox) thereby providing a mechanism for continuous supply of carbon skeletons required for nitrate assimilation. The possibility of close coordination between mitochondrial redox perturbation and nitrate reduction and its further assimilation is discussed.