196,125 research outputs found
Sesquiterpene lactones from Centaurea zuccariniana and their antimicrobial activity
No full textTwenty-nine compounds were isolated from the aerial parts of the Greek plant C. zuccariniana DC. The structures of the isolated compounds were established by means of NMR- (1H,1H-COSY, 1H,13C-HSQC, HMBC, NOESY, and ROESY) and mass-spectral analyses. These compounds comprise 13 sesquiterpene lactones, 14 flavonoids, two lignans, and one simple lactone. Among the isolated sesquiterpene lactones, three are new, namely one heliangolide, (1E,4Z)-15-hydroxy-8α-O-(4′- acetoxy-3′-hydroxy-2′-methylidenebutanoyl)-6βH, 7αH-germacra-1,4,11(13)-trien-6,12-olide; and two eudesmanolides, 8α-(4′,5′-diacetoxyangeloyl)sonchucarpolide and one unusual eudesmanolide with an oxygenated bridge linking C(1) and C(4), named zuccarinin. The main sesquiterpene lactones were malacitenolide, cnicin, and 4′-O-acetylcnicin. These results are in agreement with those obtained from the previously studied Greek Centaurea sp. belonging to the section Acrolophus (Cass.) DC.; this finding could be of chemotaxonomic significance for the genus Centaurea. The in vitro antimicrobial activities of the isolated new sesquiterpene lactones were against eight bacteria and eight fungal species. A 96-well microbioassay procedure for fast and easy evaluation of antibacterial and antifungal activities was applied to compare these compounds with commercial antibiotic and fungicide standards, and with previously isolated analogous sesquiterpene lactones tested by the same bioassay. All of the compounds tested showed moderate antibacterial, but significant antifungal activities; the present results corroborate with previous data, indicating that these types of compounds exhibit low or moderate antibacterial, but potent antifungal activities. The unusual eudesmanolide zuccarinin proved to be the most potent among the present tested sesquiterpene lactones, as well as among all previously tested eudesmanolides isolated from Greek Centaurea sp. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich
Antimicrobial activity of secondary metabolites isolated from Centaurea spruneri boiss. & heldr
No full textTwo coumarins, scopoletin (1) and isoscopoletin (2), two simple phenolic acids, protocatechuic acid (3) and isovanillic acid (4) and one flavonoid, eriodictyol (5) were isolated from the aerial parts of Centaurea spruneri. The structure of the compounds was established by spectroscopic methods. The in vitro antimicrobial activity of the isolated compounds was tested against eight bacteria and eight fungal species, using a microdilution method. All compounds tested showed moderate antibacterial and antifungal activities. Their minimum inhibitory concentrations were in the range 0.655-2.38 μmol ml-1 and their minimal bactericidal concentrations ranged from 0.694 to 4.15 μmol ml-1 against the tested bacterial species. All compounds showed fungistatic activity at 0.259-2.38 μmol ml-1 and fungicidal at 0.69-2.6 μmol ml-1 against all fungi tested. © 2011 Copyright (CC) SCS
Isolation and structural elucidation of two secondary metabolites from the filamentous fungus Penicillium ochrochloron with antimicrobial activity
No full textIn this investigation, the extracts of filamentous fungi exhibited inhibitory effect on the growth of Gram positive and Gram negative bacteria, as well as against the yeast Candida albicans. Penicillium ochrochloron has been proven as the most active fungus against all tested microorganisms. Further bio-guided chemical analysis of P. ochrochloron afforded two components with antimicrobial activity identified as (-) 2, 3, 4-trihydroxybutanamide and (-) erythritol. © 2005 Elsevier B.V. All rights reserved
A novel sesquiterpene lactone from Centaurea pullata: Structure elucidation, antimicrobial activity, and prediction of pharmacokinetic properties
No full textA novel elemanolide with an α-methyl-γ-lactone moiety, 8α-O-(4-hydroxy-2-methylenebutanoyloxy)melitensine, in addition to four known sesquiterpene lactones also bearing the same lactone ring, melitensin, 11β,13 dihydrosalonitenolide, 8α-hydroxy-11β,13-dihydro-4-epi-sonchucarpolide, and 8α-hydroxy-11β,13-dihydro-onopordaldehyde have been isolated from the aerial parts of Centaurea pullata. The in vitro antibacterial and antifungal activities of the isolated sesquiterpene lactones were tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used. Moreover, the pharmacokinetic profile of these compounds was investigated using computational methods. © 2008 Elsevier Ltd. All rights reserved
The influence of chemical composition of high-speed steels on the wear during cutting ad erosion tests
No full textThe paper presents the results of investigations of the 5% cobalt and 2% molybdenum additions in the W-Mo-V and W-V high-speed steels of the 9-2-2, 11-2-2 and 11-0-2 types with economically designed chemical composition on the wear mechanism during cutting and erosion tests. The 5% cobalt addition results in increasing the secondary hardness effect by 1.6 to 1.9 HRC, depending on a steel grade. Secondary hardness effect is caused by the dispersive carbides of the M4C3 type and martensite transformation of the retained austenite. The maximum secondary hardness effect about 66.3-67.6 HRC, depending on a grade of steel, occurs in each steel after tempering at 540oC and austenitizing at 1240oC. The 5% cobalt addition results in enhancing the working properties of tools, longer tool life and makes it possible to increase cutting speed by about 50%, compared with the steels of identical concentration of other alloying elements but without cobalt addition. Cobalt does not have any significant influence on erosion resistance, which is independent of the steel hardness but depends on molybdenum addition in steel
The Triazole Ring as a Privileged Scaffold for Putative Antifungals: Synthesis and Evaluation of a Series of New Analogues
No full textThe significant antifungal activity of a series of novel 1,2,4-triazole derivatives against different strains of Candida albicans, Candida krusei and Aspergillus fumigatus, compared to the commercial fungicides ketoconazole and itraconazole, is reported. Systemic mycosis and invasive fungal infections, whether from immunodeficiency or hospital-acquired infection, have been on an upward trend for several years. The 1,2,4-triazole ring substituted with other aromatic and heteroaromatic systems plays an important role in the field of antifungal drug discovery and development. Thus, an extensive series of 29 triazoles, substituted in different positions with a variety of aromatic rings, has been designed, synthesized, and evaluated for their fungicidal activity. Almost all the agents tested in vitro showed high activity against all examined fungal strains. It is noteworthy that, in the case of A. fumigatus, all the examined compounds achieved equal or higher antifungal activity than ketoconazole, but less activity than itraconazole. Among all the derivatives studied, the dichlorourea analogue and bromo-substituted triazole stand out as the most promising compounds. Quantitative structure-activity relationship (QSAR) models were built for a systematic structure-activity relationship (SAR) profile to explain and potentially explore the potency characteristics of 1,2,4-triazole analogues
Cobalt effect on structure, cutting ability and erosion resistance of W-Mo-V high speed steels
No full textAntimicrobial properties of Quercus ilex L. Proanthocyanidin dimers and simple phenolics: Evaluation of their synergistic activity with conventional antimicrobials and prediction of their pharmacokinetic profile
No full textThe antibacterial and antifungal activities of an ample number of phenolic compounds isolated from Quercus ilex leaves, belonging to the classes of flavonoids, proanthocyanidins, and phenolic acids, are discussed. The isolation of A type proanthocyanidin, (+)-epigallocatechin-(2β→O→7, 4β→8)-(+)-catechin (1) is reported for the first time. Its structure was established by means of highfield NMR (correlation spectroscopy, heteronuclear single quantum correlation, heteronuclear multiple bond correlation, and rotating frame Overhauser effect spectroscopy) and MS spectral analyses, while its absolute configuration was determined by circular dichroism measurements. The isolated compounds were tested for their antimicrobial effects against eight human bacterial species and 14 fungal species. In a second step, the most potent compounds were tested in combination with the conventional fungicides, bifonazole and ketoconazole, to evaluate possible synergistic effects. Results showed that proanthocyanidins 3 and 4 when combined with bifonazole and ketoconazole increase the activity of both of these conventional fungicides. Moreover, the pharmacokinetic profile of the isolated compounds was investigated using computational methods. © 2011 American Chemical Society
Minor sesquiterpene lactones from Centaurea pullata and their antimicrobial activity
No full textThe aerial parts of Centaurea pullata afforded, in addition to the previously isolated sesquiterpene lactones, 11β,13-dihydrocnicin and 11β,13-dihydro-19-desoxycnicin, three minor sesquiterpene lactones, namely, a new germacranolide, 8α-0-(4-acetoxy-5-hydroxyangeloyl)-11β,13- dihydrocnicin, and two new eudesmanolides, 8α-0-(4-hydroxy-2- methylenebutanoyloxy)-11β,13-dihydrosonchucarpolide and 8α-0-(4-hydroxy-2-methylenebutanoyloxy)-11β,13-dihydro-4-epi- sonchucarpolide. The in vitro antimicrobial activity of all isolated sesquiterpene lactones was tested against six bacteria and eight fungal species, using a microdilution method. All compounds tested showed greater antibacterial and antifungal activities than the positive controls used. © 2007 American Chemical Society and American Society of Pharmacognosy
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
- …
