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At least 433 records · Page 24Linked to original sources
PubMed2002

Core-modified sordaricin derivatives: synthesis and antifungal activity.

Core-modified sordaricin derivatives were prepared via biotransformation followed by chemical modification and tested for antifungal activity. The antifungal activity proved to be very sensitive to modifications in the sterics and/or lipophilicity of the diterpene skeleton. Introduction of polar groups such as hydroxyl in the diterpene core results in loss of potency while small and lipophilic groups such as fluorine and the 7,8-olefin are well tolerated.

Antifungal Agents↗
PubMed2002

Chalcones and flavonoids as anti-tuberculosis agents.

A series of flavonoids, chalcones and chalcone-like compounds were evaluated for inhibitory activity against Mycobacterium tuberculosis H37Rv. Among them, eight compounds exhibited >90% inhibition on the growth of the bacteria at a concentration of 12.5 microg/mL. Chalcones 1-(2-hydroxyphenyl)-3-(3-chlorophenyl)-2-propen-1-one (22) and 1-(2-hydroxyphenyl)-3-(3-iodophenyl)-2-propen-1-one (37) demonstrated 90 and 92% inhibition, respectively. Chalcone-like compounds (heterocyclic ring-substituted 2-propen-1-one) 1-(4-fluorophenyl)-3-(pyridin-3-yl)-2-propen-1-one (48), 1-(3-hydroxyphenyl)-3-(phenanthren-9-yl)-2-propen-1-one (49), 1-(pyridin-3-yl)-3-(phenanthen-9-yl)-2-propen-1-one (50) and 1-(furan-2-yl)-3-phenyl-2-propen-1-one (51) exhibited 98, 97, 96 and 96% inhibition, respectively. The actual minimum inhibitory concentrations (MIC), defined as the lowest concentration inhibiting 99% of the inoculum, for 22, 37, 48, 49, 50 and 51 were 20.3, 31.5, 48.3, >35.7, 6.8 and 19.2, respectively. A hydrophobic substituent on one aromatic ring, and a hydrogen-bonding group on the other aromatic ring resulted in increased anti-TB activity of the chalcones and chalcone-like compounds. Flavones and flavanones are more geometrically constrained than the corresponding chalcone analogues. The decreased activity of the flavones with respect to the chalcones may be due to the confinement of the terminal aromatic rings to the same plane.

Antitubercular Agents↗
PubMed2003

Three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of tricyclic oxazolidinones as antibacterial agents.

Oxazolidinones exemplified by eprezolid and linezolid are a new class of antibacterials that are active against Gram positive and anaerobic bacteria including methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE) and vancomycin resistant enterococci (VRE). In an effort to have a better antibacterial agent in the oxazolidinone class, we have performed three-dimensional quantitative structure-activity relationship (3D-QSAR) studies for a series of tricyclic oxazolidinones. 3D-QSAR studies were performed using the Comparative Molecular Field Analysis (CoMFA) and Comparative Molecular Similarity Indices Analysis (CoMSIA) procedures. These studies were performed using 42 compounds; the QSAR model was developed using a training set of 33 compounds. The predictive ability of the QSAR model was assessed using a test set of 9 compounds. The predictive 3D-QSAR models have conventional r(2) values of 0.975 and 0.940 for CoMFA and CoMSIA respectively; similarly, cross-validated coefficient q(2) values of 0.523 and 0.557 for CoMFA and CoMSIA, respectively, were obtained. The CoMFA 3D-QSAR model performed better than the CoMSIA model.

Anti-Infective Agents↗
PubMed2002

Genetically-modified-animal models for human infections: the Listeria paradigm.

Several human pathogens exhibit a restricted host-tropism, relying on the species-specific interaction of microbial ligand(s) with host receptor(s). This specificity accounts for some of the difficulties in modeling human infections in animals. The discovery of L. monocytogenes host-specificity and elucidation of the underlying mechanism has led to the generation of transgenic mice expressing one of its human receptors, E-cadherin. This model is presented here as a paradigm of a genetically-modified-animal model for studying a human infectious disease.

Animals↗
PubMed2004

Investigating the importance of the flexible hinge in caerin 1.1: solution structures and activity of two synthetically modified caerin peptides.

Caerin 1.1 is a potent broad-spectrum antibacterial peptide isolated from a number of Australian frogs of the Litoria genus. In membrane-like media, this peptide adopts two alpha-helices, separated by a flexible hinge region bounded by Pro15 and Pro19. Previous studies have suggested that the hinge region is important for effective orientation of the two helices within the bacterial cell membrane, resulting in lysis via the carpet mechanism. To evaluate the importance of the two Pro residues, they were replaced with either Ala or Gly. The antibacterial activity of these two peptides was tested, and their three-dimensional structures were determined using two-dimensional NMR spectroscopy and restrained molecular dynamics calculations. The resulting structures indicate that the central hinge angle decreases significantly upon replacement of the Pro residues with Gly and to a further extent with Ala. This trend was mirrored by a corresponding decrease in antibiotic activity, further exemplifying the necessity of the hinge in caerin 1.1 and related peptides. In a broader context, the use of Pro, Gly, and Ala variants of caerin 1.1 has enabled the relationship between conformational flexibility and activity to be directly investigated in a systematic manner.

Alanine↗
PubMed2004

Role of speciation in organotin toxicity to the yeast Candida maltosa.

Assessment of organometal pollution requires an understanding of the various processes that influence the bioavailability and toxicity of the contaminant. Organotins may exist as both cationic species and neutral hydroxides in aqueous solution, with the formation of chloride species in the presence of Cl-. Although these species have different chemical properties, there is very little information on the influence of speciation on organotin and microbial cell interactions. Tributyltin (TBT) and triphenyltin (TPT) interactions with the yeast Candida maltosa were investigated between pH 3.5 and 7.5 and in up to 0.5 M NaCl at pH 5.5. Toxicity increased with both pH and NaCl concentration and the mechanisms of interaction depended on the species present in solution. TBT and TPT interacted by different mechanisms, as evidenced by action on membrane fluidity. Furthermore, there was a strong correlation between toxicity and overall octanol-water distribution ratio (D(OW)) of organotin compounds. Triorganotin cations are less toxic than triorganotin hydroxides, which are in turn less toxic than triorganotin chlorides. These findings underline the importance of speciation effects on organotin interactions in the environment.

Candida↗
PubMed2005

Amphiphilic polymethacrylate derivatives as antimicrobial agents.

We have investigated the structure-activity relationship of cationic amphiphilic polymethacrylate derivatives in antimicrobial and hemolytic assays. The polymers were prepared by radical copolymerizations of N-(tert-butoxycarbonyl)aminoethyl methacrylate and butyl methacrylate in the presence of methyl 3-mercaptopropionate as a chain transfer agent to give precursor polymers protected with a tert-butoxycarbonyl (Boc) group. Subsequent treatment of the Boc-protected polymers with TFA affords the desired cationic random copolymers. We examined antimicrobial and hemolytic activities of a series of polymers having a wide range of mole percentage of butyl groups (0-60%) in three different molecular weight (MW) ranges. The smallest polymers (MW < 2000) showed the lowest MIC and reduced hemolytic activity compared to that of the higher MW ones. In addition, polymers containing a high percentage of butyl groups are less selective for bacterial cells than their less hydrophobic counterparts.

Anti-Infective Agents↗
PubMed2003

Synthesis of substituted 6-anilinouracils and their inhibition of DNA polymerase IIIC and Gram-positive bacterial growth.

Certain substituted 6-anilinouracils are potent and selective inhibitors of Gram+ bacterial DNA polymerase IIIC (pol IIIC). In addition, analogues with 3-substituents in the uracil ring have potent antibacterial activity against Gram+ organisms in culture. In an attempt to find optimal anilino substituents for pol IIIC binding and optimal 3-substituents for antibacterial activity, we have prepared several series of 3-substituted-6-aminouracils and assayed their activity against pol IIIC from Bacillus subtilis and a panel of Gram+ and Gram- bacteria in culture. The 6-(3-ethyl-4-methylanilino) group and closely related substituent patterns maximized pol IIIC inhibition potency. Among a series of 3-(substituted-butyl)-6-(3-ethyl-4-methylanilino)uracils, basic amino substituents increased pol IIIC inhibition, but decreased antibacterial activity. The most potent antibacterials were simple hydroxybutyl and methoxybutyl derivatives, and hydrophobically substituted piperidinylbutyl derivatives.

Aniline Compounds↗
PubMed2003

Soft antimicrobial agents: synthesis and activity of labile environmentally friendly long chain quaternary ammonium compounds.

A series of soft quaternary ammonium antimicrobial agents, which are analogues to currently used quaternary ammonium preservatives such as cetyl pyridinium chloride and benzalkonium chloride, were synthesized. These soft analogues consist of long alkyl chain connected to a polar headgroup via chemically labile spacer group. They are characterized by facile nonenzymatic and enzymatic degradation to form their original nontoxic building blocks. However, their chemical stability has to be adequate in order for them to have antimicrobial effects. Stability studies and antibacterial and antiviral activity measurements revealed relationship between activity, lipophilicity, and stability. Their minimum inhibitory concentration (MIC) was as low as 1 microg/mL, and their viral reduction was in some cases greater than 6.7 log. The structure-activity studies demonstrate that the bioactive compounds (i.e., MIC for Gram-positive bacteria of <10 microg/mL) have an alkyl chain length between 12 and 18 carbon atoms, with a polar headgroup preferably of a small quaternary ammonium group, and their acquired inactivation half-life must be greater than 3 h at 60 degrees C.

Alkylation↗
PubMed2004

Distamycin analogues with enhanced lipophilicity: synthesis and antimicrobial activity.

Forty-eight heterocyclic amino acid trimers, analogues of distamycin, with a number of features that enhance lipophilicity are described. They contain alkyl or cycloalkyl groups larger than methyl; some are N-terminated by acetamide or methoxybenzamide and are C-terminated by dimethylaminopropyl or aliphatic heterocylic aminopropyl substituents. The ability of these compounds to bind principally to AT tracts of DNA has been evaluated using capillary zone electrophoresis. Significant antimicrobial activity against key organisms such as MRSA and Candida albicans is shown by several compounds, especially those containing a thiazole. Moreover, these compounds have low toxicity with respect to several mammalian cell lines.

Animals↗
PubMed2002

The impact of polyene, azole, and DNA analogue antimycotics on the cell surface hydrophobicity of Candida albicans and Candida tropicalis in HIV infection.

Oral candidiasis is the most common opportunistic infection in individuals infected with the human immunodeficiency virus. Though Candida albicans is the major aetiological agent, non-albicans species such Candida tropicalis are now emerging as important agents of such infection. The Candida cell surface hydrophobicity (CSH) is considered a critical factor contributing to its colonization potential and virulence. It is also known that brief exposure to sub-cidal concentrations of antifungal agents is a likely scenario in the oral environment where the administered drugs are diluted continuously due to the flushing action of saliva. Hence the objective of the present study was to compare the CSH of 10 isolates each of C. albicans and C. tropicalis from HIV-infected individuals following brief exposure (1 hour) of isolates to sub-therapeutic concentrations of nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine. The CSH was assessed by a previously described biphasic aqueous-hydrocarbon assay. The mean percentage reduction of CSH of C. albicans following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was 27.33 (p < 0.001), 21.34 (p < 0.05), 11.74 (p > 0.05), 18.4 (p > 0.05) and 14.64 (p > 0.05) respectively. The mean percentage reduction of CSH of C. tropicalis following brief exposure to nystatin, amphotericin B, ketoconazole, fluconazole and 5-flurocytosine was 33.81 (p < 0.01), 28.88 (p < 0.01), 12.6 (p > 0.05), 21.53 (p > 0.05) and 17.68 (p > 0.05) respectively. A significant interspecies variation in CSH was observed for nystatin and amphoterecin B. Overall the results reveal that the CSH of C. albicans is affected to a significantly lesser degree compared with C. tropicalis when exposed to the antifungals. These data further illustrate another mode of action of antifungals on Candida leading to a reduction in the CSH and thereby the yeast adherence to host tissues.

AIDS-Related Opportunistic Infections↗
PubMed2002

Microbe-plant interactions: principles and mechanisms.

The present status of research on the molecular basis of microbe-plant interactions is discussed. Principles and mechanisms which play a role in the interactions of microbial pathogens, biofertilizers, phytostimulators, rhizoremediators and biocontrol agents with the plants are treated. Special emphasis is given to colonization, phase variation, two-component systems, quorum sensing, complex regulation of the syntheses of extracellular enzymes and secondary metabolites, Type 4 pili and Type III and Type IV secretion systems.

Bacteria↗
PubMed1992

Emerging strategies for enhancing crop resistance to microbial pathogens.

There are marked differences in the pattern of host gene expression in incompatible plant:microbial pathogen interactions compared with compatible interactions, associated with the elaboration of inducible defenses. Constitutive expression of genes encoding a chitinase or a ribosome-inactivating protein in transgenic plants confers partial protection against fungal attack, and a large repertoire of such antimicrobial genes has been identified for further manipulation. In addition, strategies are emerging for the manipulation of multigenic defenses such as lignin deposition and synthesis of phytoalexin antibiotics by overexpression of genes encoding rate determining steps, modification of transcription factors or other regulatory genes, and engineering production of novel phytoalexins by interspecies transfer of biosynthetic genes. The imminent cloning of disease resistance genes, further molecular dissection of stress signal perception and transduction mechanisms, and identification of genes that affect symptom development will provide attractive new opportunities for enhancing crop protection. Combinatorial integration of these novel strategies into ongoing breeding programs should make an important contribution to effective, durable field resistance.

Amino Acid Sequence↗
PubMed2026

Integrating multi-omics technologies to decipher microbiome functions.

Multi-omics approaches have revolutionized our understanding of microbial communities by enabling simultaneous interrogation of genomic, transcriptomic, proteomic, and metabolomic data. The systematic integration and analysis of these deep datasets help decipher the functional roles of microbiomes, providing critical insights into microbial activities, interactions, and dynamics across diverse environments. Biological complexity makes multi-omics analysis of a single, isolated organism demanding but highly informative, yet this complexity increases further when samples comprise hundreds to thousands of individual species. As microbiome research continues to expand into clinical, environmental, and engineered systems, standardized workflows, benchmarked datasets, and community-driven initiatives are essential to ensure reproducibility, standardization and interpretability. Establishing and disseminating best practices for experimental design, data processing, and integrative analyses will be critical for maximizing comparability and scientific rigor across studies. This perspective highlights recent advances in multi-omics microbiome research, outlines key obstacles in data integration and metadata harmonization, and proposes a collaborative roadmap for scalable, FAIR-compliant multi-omics investigations and potentially disruptive Artificial Intelligence (AI) advances comparable to those of AlphaFold in the field of microbiome science.

Multiomics↗