Synthesis,characterization and biological activity of ring-substituted 6-benzylamino-9-tetrahydropyran-2-yl and 9-tetrahydrofuran-2-ylpurine derivatives

In an attempt to improve specific biological functions of cytokinins routinely used in plant micropropagation, 33 6-benzylamino-9-tetrahydropyran-2-ylpurine (THPP) and 9-tetrahydrofuran-2-ylpurine (THFP) derivatives, with variously positioned hydroxy and methoxy functional groups on the benzyl ring, were prepared. The new derivatives were prepared by condensation of 6-chloropurine with 3,4-dihydro-2H-pyran or 2,3-dihydrofuran and then by the condensation of these intermediates with the corresponding benzylamines. The prepared compounds were characterized by elemental analyses, TLC, HPLC, melting point determinations, CI+ MS and ¹H NMR spectroscopy. The cytokinin activity of all the prepared derivatives was assessed in three classical cytokinin bioassays (tobacco callus, wheat leaf senescence and Amaranthus bioassay). The derivatives 6-(3-hydroxybenzylamino)-9-tetrahydropyran-2-ylpurine (3) and 6-(3-hydroxybenzylamino)-9-tetrahydrofuran-2-ylpurine (23) were selected, because of the high affinity of their parent compound meta-topolin (mT, 6-(3-hydroxybenzylamino)purine) to cytokinin receptors, as model compounds for studying their perception by the receptors CRE1/AHK4 and AHK3 in a bacterial assay. Both receptors perceived these two derivatives less well than they perceived the parent compound. Subsequently, the susceptibility of several new derivatives to enzyme degradation by cytokinin oxidase/dehydrogenase was studied. Substitution of tetrahydropyran-2-yl (THP) at the N⁹ position decreased the turnover rates of all new derivatives to some extent. To provide a practical perspective, the cytotoxicity of the prepared compounds against human diploid fibroblasts (BJ) and the human cancer cell lines K-562 and MCF-7 was also assayed in vitro. The prepared compounds showed none or marginal cytotoxicity compared to the corresponding N⁹-ribosides. Finally, the pH stability of the two model compounds was assessed in acidic and neutral water solutions (pH 3–7) by high-performance liquid chromatography (HPLC).     

Enzyme‐assisted physicochemical enantioseparation processes—Part III: Overcoming yield limitations by dynamic kinetic resolution of asparagine via preferential crystallization and enzymatic racemization

The application of enantioseparation methods alone can only yield up to 50% of the desired chiral product. Thus enantioseparation becomes more attractive when accompanied by the racemization of the counter‐enantiomer. Here we present first results of dynamic kinetic resolution of L ‐asparagine (L ‐Asn) via preferential crystallization and enzymatic racemization from a racemic, supersaturated solution on a 20 mL scale. An enzyme lyophilisate (WT amino acid racemase from P. putida KT2440 (E.C. 5.1.1.10), overexpressed in E. coli BL21(DE3)) was used for in situ racemization (enzyme concentrations varying from 0 to 1 mg/mL). When preferential crystallization was applied without any enzyme, a total of 31 mg of L ‐Asn monohydrate could be crystallized, before crystal formation of d ‐Asn started. Crystallization experiments accompanied by enzymatic racemization led to a significant increase of crystallized L ‐Asn (198 mg L ‐Asn monohydrate; >92%ee) giving the first experimental proof for this new process concept of dynamic kinetic resolution via preferential crystallization and enzymatic racemization. Measurements of the racemase activity before and after the crystallization process showed no significant differences, which would allow for enzyme recovery and recycling. Biotechnol. Bioeng. 2009; 104: 1235–1239. © 2009 Wiley Periodicals, Inc.     

Synthesis, characterization and in vitro cytotoxicity of the first palladium(II) oxalato complexes involving adenine-based ligands

The first [Pd(Lⁿ)₂(ox)] xH₂O oxalato(ox) complexes involving 2-chloro-N6-(benzyl)-9-isopropyladenine (L¹; complex 1), 2-chloro-N6-(4-methoxybenzyl)-9-isopropyladenine (L²; 2), 2-chloro-N6-(2,3-dimethoxybenzyl)-9-isopropyladenine (L³; 3), 2-chloro-N6-(2,4-dimethoxybenzyl)-9-isopropyladenine (L⁴; 4), and 2-chloro-N6-(4-methylbenzyl)-9-isopropyladenine (L⁵; 5) have been synthesized by the reactions of potassium bis(oxalato)palladate(II) dihydrate, [K₂Pd(ox)₂]·2H₂O, with the mentioned organic compounds (H₂ox = oxalic acid; x = 0 for 1-3 and 5 or 2 for 4). Elemental analyses (C, H, N), FTIR, Raman and NMR (¹H, ¹³C, ¹⁵N) spectroscopies, conductivity measurements and thermal studies (thermogravimetric and differential thermal analyses, TG/DTA) have been used to characterize the prepared complexes. The molecular structures of [Pd(L²)₂(ox)] (2) and [Pd(L⁵)₂(ox)]·L⁵·Me₂CO (5·L⁵·Me₂CO) have been determined by a single crystal X-ray analysis. The geometry of these complexes is slightly distorted square-planar with two appropriate Lⁿ (n = 2 or 5) molecules mutually arranged in the head-to-head (2) or head-to-tail (5) orientation. The Lⁿ ligands are coordinated to the central Pd(II) ion via the N7 atoms. The same conclusions regarding the binding properties of L¹-L⁵ ligands can be made based on multinuclear NMR spectra. In vitro cytotoxicity of the complexes 1-5 has been evaluated against human chronic myelogenous leukaemia (K562) and human breast adenocarcinoma (MCF7) cancer cell lines. Significant cytotoxicity has been determined for the complexes 3 (IC₅₀ = 6.2 μM) and 5 (IC₅₀ = 6.8 μM) on the MCF7 cell line, which is even better than that found for the well-known and widely-used platinum-bearing antineoplastic drugs, i.e. oxaliplatin and cisplatin.     

Novel platinum(II) and palladium(II) complexes with cyclin-dependent kinase inhibitors: synthesis, characterization and antitumour activity

The Pt(II) and Pd(II) complexes of the types cis-[Pt(L(1))(2)Cl(2)].H(2)O (1), cis-[Pt(L(2))(2)Cl(2)].3H(2)O (2), trans-[Pd(L(1))(2)Cl(2)].H(2)O (3), trans-[Pd(L(2))(2)Cl(2)].H(2)O (4), trans-[Pd(L(3))(2)Cl(2)].2DMF (5) and trans-[Pd(L(4))(2)Cl(2)].2DMF (6) (L(1)-L(4)=cyclin-dependent kinase inhibitors derived from 6-benzylamino-9-isopropylpurine) have been prepared and characterized. The complexes have been studied by elemental analyses, conductivity measurements, ES+ MS, FT-IR, (1)H, (13)C and (195)Pt NMR spectra, differential scanning calorimetry and thermogravimetric analysis. The molecular structures of L(1), trans-[Pd(L(3))(2)Cl(2)].2DMF (5) and trans-[Pd(L(4))(2)Cl(2)].2DMF (6) have been determined by single crystal X-ray analysis. The complexes have been tested in vitro due to their presumable anticancer activity against the following human cancer cell lines: K-562, MCF7, G-361 and HOS. Satisfying results were obtained for the complex 1 with IC(50) values of 6 microM acquired against G-361 as well as against HOS cell lines. The lowest values of IC(50) were achieved for the complexes 3 and 4 against MCF 7 cell line with IC(50) 3 microM(for 3) and also 3 microM (for 4).     

Preparation and biological activity of 6-benzylaminopurine derivatives in plants and human cancer cells

To study the structure-activity relationships of aromatic cytokinins, the cytokinin activity at both the receptor and cellular levels, as well as CDK inhibitory and anticancer properties of 38 6-benzylaminopurine (BAP) derivatives were compared in various in vitro assays. The compounds were prepared by the condensation of 6-chloropurine with corresponding substituted benzylamines. The majority of synthesised derivatives exhibited high activity in all three of the cytokinin bioassays employed (tobacco callus, wheat senescence and Amaranthus bioassay). The highest activities were obtained in the senescence bioassay. For some compounds tested, significant differences of activity were found in the bioassays used, indicating that diverse recognition systems may operate and suggesting that it may be possible to modulate particular cytokinin-dependent processes with specific compounds. Position-specific steric and hydrophobic effects of different phenyl ring substituents on the variation of biological activity were confirmed. In contrast to their high activity in bioassays, the BAP derivatives were recognised with much lower sensitivity than trans-zeatin in both Arabidopsis thaliana AHK3 and AHK4 receptor assays. The compounds were also investigated for their effects on cyclin-dependent kinase 2 (CDK2) and for antiproliferative properties on cancer and normal cell lines. Several of the tested compounds showed stronger inhibitory activity and cytotoxicity than BAP. There was also a significant positive correlation of the inhibitory effects on human and plant CDKs with cell proliferation of cancer and cytokinin-dependent tobacco cells, respectively. This suggests that at least a part of the antiproliferative effect of the new cytokinins was due to the inhibition of CDK activity.     

Comparative study of RT23 and IC-65 tuberculins tested on children with tuberculosis

This study, conducted in 2009, proposed to evaluate and compare the biological potency of two different tuberculins, RT23 (Statens Serum Institute, Copenhagen) and IC-65 (Cantacuzino Institute, Bucharest) when administered to 89 children with confirmed tuberculosis, admitted to Paediatric Department of Pneumophtysiology Institute, Bucharest. Mean age of subjects was 10.4 years [SD (standard deviation) = 5.2 years; variance = 27.2], and sex distribution in the group was: 55.1% girls and 44.9% boys. Tuberculin skin tests were performed using Mantoux method simultaneously with the two tuberculins in the same concentration, 2TU (tuberculin units)/0.1 ml. RT23 skin test reactions ranged from 8 mm to 18 mm (mean = 12.8 mm, SD = 2.1 mm, variance = 4.4; median = 12.0), and IC-65 reactions ranged from 8 mm to 18 mm (mean = 13.1 mm; SD = 2.1 mm; variance = 4.3; median = 13.0). The mean difference in paired reaction sizes for the two reagents was 0.04 mm and was not statistically different from zero (P value = 0.3). The difference in reaction sizes was = 2 mm in 70.8% and = 5 mm in 7.9% patients. With a cutoff of 10 mm to define a positive reaction, the results were highly correlated with a sensitivity of 98.9% for RT23 and 97.8% for IC-65. No statistically significant difference was established for the efficacy of the two commercially available PPD TST reagents, both tuberculins appearing to have equivalent potency.     

The establishment of resistance phenotypes for bacteria isolated from outpatients in urine cultures

From 1911 outpatients, who addressed a Timi?oara private clinical laboratory, from January to December 2005, we collected 1,889 urine cultures, 431 being positive. Bacteria identification was generally done using morphological, cultural, biochemical characters and pathogenicity tests. Sensitivity testing to antimicrobial medical drugs was done by using the classical diffusion Kirby-Bauer method and the automatic analyzer Osiris, also. The main bacteria involved in the etiology of these infections were represented by Enterobacteriaceae, head of the list being Escherichia coli (81.21%), followed by Klebsiella pneumoniae (8.35%) and Proteus mirabilis (3.02%). We also isolated Gram positive cocci (in a much smaller proportion), mainly represented by Enterococcus faecalis (1.16%), Staphylococcus aureus (0.93%), Streptococcus agalactiae, and also Gram negative non-fermentative bacilli, such as Pseudomonas aeruginosa (0.93%) or Acinetobacter baumanii (0.23%). As soon as we performed the sensitivity tests, we divided them in resistance phenotypes: Most of the Enterobacteriaceae were integrated in the wild phenotype, followed by the penicillinase producing phenotype. An E. coli strain (0.29%) and 3 Klebsiella pneumoniae strains (8.33%) were integrated in the large spectrum, multidrug resistant, beta-lactamase producing phenotype, also associated with resistance to fluoroquinolones and aminoglycosides; Non-fermentative bacilli did not present special resistance problems, the four Pseudomonas aeruginosa strains were integrated in the wild phenotype (secreting induced chromosomal cephalosporinase). As for Staphylococcus aureus it was identified a strain having fluoroquinolone resistance, two strains secreting penicillinase and having a K (Nm) phenotype and a strain secreting penicillinase only. Antibiotic resistance represents a major concern for patients, physicians, healthcare managers, and policymakers. The use of antibiotics is closely linked with the development of acquired antibiotic resistance.     

Recommendations for fungal opportunistic infections prevention in persons infected with human immunodeficiency virus

Fungal infections have become important causes of morbidity and mortality in immunocompromised hosts, including those with the acquired immune deficiency syndrome (AIDS). Although significant therapeutic advances are being made in the field of antiretroviral therapy, parallel advances must be attained in the management of secondary infections, including those due to fungi. As increasing numbers of people with HIV infection come in to medical attention, the problem of fungal infections will also increase, requiring innovative approaches toward understanding the pathogenesis of these infections and developing new diagnostic and therapeutic modalities. A better understanding is required for the immunopathogenesis of fungal infections. Improved understanding of new and established antifungal agents in conjunction with ART agents as well as immune modulators, should yield important advances in prevention, control and treatment of fungal infections of HIV infected people.