Preparation and biological activity of 13-substituted retinoic acids

13-Demethyl or 13-substituted all-E- and 9Z-retinoic acids were synthesized using a palladium-catalyzed coupling reaction of enol triflates and tributylstannylolefins. Their biological activities were then measured. The 13-ethyl analogs exhibited approximately one-half of the antiproliferative and differentiation-inducing activity of ATRA in HL-60 cells. In contrast, in the 9Z-derivatives, all analogs, except for the 13-butyl derivatives, showed apoptosis-inducing activity.     

Preparation and biological activity of 5,6-dihydro-5-azapyrimidine nucleosides

The reaction of 5-azapyrimidine nucleosides Ia-IXa with zinc powder in acetic acid afforded the respective 5,6-dihydro derivatives Ib-IXb in high yields. This procedure represents a convenient and general method for preparation of the title compounds. The effects of some dihydro-5-azapyrimidine nucleosides on the growth in vitro of L1210 mouse leukemic cells were estimated.     

Preparation and biological activity of novel tricyclic GPIIb/IIIa antagonists

Antagonists of the glycoprotein GPIIb/IIIa are a promising class of antithrombotic agents offering potential advantages over present antiplatelet agents (i.e., aspirin and ticlopidine). Novel tricyclic nonpeptidal GPIIb/IIIa antagonists have been prepared and evaluated in vitro as antagonists of fibrinogen binding to the purified GPIIb/IIIa receptor and as inhibitors of platelet aggregation. The work presented demonstrates the robustness of the benzodiazepinedione (BZDD) scaffold, which can be functionalized at the N¹---C² amide as well as at C⁷, to provide structural diversity and allow optimization of the physiochemical and pharmacological properties of the BZDD based GPIIb/IIIa antagonists. In addition, the resulting new class of tricyclic GPIIb/IIIa antagonists could be used to probe for additional binding interactions on the GPIIb/IIIa receptor and perhaps lead to BZDD based GPIIb/IIIa antagonists with increased potency. The tricyclic molecules reported herein demonstrate that a heterocyclic ring can be fused to the benzodiazepinedione scaffold with retention of anti-aggregatory potency and in the case of tetrazole 30i, increased potency relative to the bicyclic analogue 1c.     

Preparation, biological activity and endogenous occurrence of N6-benzyladenosines

Cytokinin activity of forty-eight 6-benzyladenosine derivatives at both the receptor and cellular levels as well as their anticancer properties were compared in various in vitro assays. The compounds were prepared by the condensation of 6-chloropurine riboside with corresponding substituted benzylamines and characterized by standard collection of physico-chemical methods. The majority of synthesized derivatives exhibited high activity in all three of the cytokinin bioassays used (tobacco callus, wheat leaf senescence and Amaranthus bioassay). The highest activities were observed in the senescence bioassay. For several of the compounds tested, significant differences in activity were found between the bioassays used, indicating that diverse recognition systems may operate. This suggests that it may be possible to modulate particular cytokinin-dependent processes with specific compounds. In contrast to their high activity in bioassays, the tested compounds were recognized with only very low sensitivity in both Arabidopsis thaliana AHK3 and AHK4 receptor assays. The prepared derivatives were also investigated for their antiproliferative properties on cancer and normal cell lines. Several of them showed very strong cytotoxic activity against various cancer cell lines. On the other hand, they were not cytotoxic for normal murine fibroblast (NIH/3T3) cell line. This anticancer activity of cytokinin ribosides may be important, given that several of them occur as endogenous compounds in different organisms.     

Preparation,characterization, biological activity and metabolism of all-trans retinoyl fluoride

All-trans retinoyl fluoride was prepared by treating all-trans retinoic acid with diethylaminosulfurtrifluoride. The crystalline product, which was characterized by melting point, infrared, ¹H-NMR, ¹⁹F-NMR and elementary analysis, showed λ_max at 382 nm in hexane (ε = 4.98·10⁴ M^?1·cm^?1) and at 392 nm in methanol (ε = 4.60·10⁴ M^?1·cm^?1). Its biological activity in the rat growth assay, relative to all-trans retinyl acetate, was 22% ± 10%. Upon oral administration for 5 days to vitamin A-depleted rats, retinoyl fluoride (1020 μg) was rapidly metabolized to a polar metabolite fraction and, in the intestine, to an unstable retinol-like metabolite, purpotedly 15-fluororetinol. Upon administering intraperitoneally smaller doses (47–94 μg) of [11-³H]retinoyl fluoride, which was synthesized from [11-³H] retinoic acid, radioactive retinoic acid was noted in the liver and plasma but not in the intestine. As expected, a radioactive polar fraction appeared in the intestine and liver, but radioactive retinol, retinyl ester and some common oxidation products were not detected. Of the administered radioactivity, 72% was excreted in the urine, and only 4% was found in the feces over a 7-day period. Hydrolysis of the urine gave a radioactive fraction with a polarity similar to that of retinoic acid. Retinoyl fluoride also reacts readily with glycine to yield N-retinoyl glycine. Thus, the biological activity of retinoyl fluoride can be attributed to the formation of retinoic acid, probably by way of N-retinoyl derivatives. A possible pathway for its metabolism is presented.     

Antimicrobial activity of trialkylgermanium acetates and the influence of the medium

A continued study of the antimicrobial activity of a series of trialkylgermanium acetates has confirmed earlier findings that the most active compounds against fungi are the ethyl and propyl derivatives, whereas for optimum antibacterial activity the chain length has to be somewhat greater. All fungi but only a few of the bacteria tested appear to be sensitive.Incorporation of blood in the medium abolishes antibacterial activity but leaves antifungal activity unaltered.     

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.     

Preparation and biological activity of molecular probes to identify and analyze jasmonic acid-binding proteins

Several types of jasomonic acid (JA) derivatives, including JA--amino acid conjugates, a JA--biotin conjugate, a JA--dexamethasone heterodimer, and a JA-fluoresceine conjugate, were prepared as candidates for molecular probes to identify JA--binding proteins. These JA derivatives, excepting the JA--fluoresceine conjugate, exhibited significant biological activities in a rice seedling assay, a rice phytoalexin-inducing assay, and/or a soybean phenylalanine ammonia-lyase-inducing assay. These JA derivatives could therefore be useful probes for identifying JA--binding proteins. The activity spectra of the prepared compounds were different from each other, suggesting that different types of JA receptors were involved in the perception of JA derivatives in the respective bioassays.     

Preparation and analysis of biological activity of the secreted proteins of the Noggin family

Methods for preparation of recombinant physiologically active proteins of the Noggin family (Noggin1 and Noggin2) of the clawed frog Xenopus laevis that are capable of interaction with BMP factors of the TGF-beta superfamily have been developed. Structures were designed for the expression of Noggin1 and Noggin2 proteins allowing us to produce them from the directly microinjected synthetic mRNA in the cells of developing embryos of the clawed frog, as well as in the prokaryotic expression system. Target proteins contained three Myc-epitopes at the N-terminal. Introduction of these’ tags’ allowed comparison of the expression level of the Noggin1 and Noggin2 proteins, isolation on the affinity immunosorbent, and demonstration of biological activity of the isolated Noggin-proteins through the analysis of their ability to bind the BMP4 factor of the TGF-beta superfamily with coimmunoprecipitation method.     

Simple synthesis of novel diphenylsulfapyrimidine acetates from chalcones and their antimicrobial activity

Given the significant low yield (19-43%) in reported results on the cyclocondensation of sulfaguanidine acetate with chalcones, a careful reinvestigation was carried out. A new series of chalcones, bearing electron-attracting groups in the aromatic moiety, have been used as precursors in the synthesis of diphenylsulfapyrimidine acetates with good yield. All synthesized compounds were active against G(+)- and G(-)-bacteria, and fungi. Combination of substituents (Cl, OMe, NO2, etc.) enhanced antimicrobial activity. Derivative with two NO2 groups exhibits an activity comparable with sulfadiazine.     

Nanocomplexes of recombinant proteins and polysialic acid: Preparation,characteristics, and biological activity

A preparation of nanocomplexes containing recombinant proteins (interferons α2b and β1b, insulin, and human granulocyte colony stimulating factor) and natural polysialic acid (PSA) has been described. The incorporation of protein into the complex changes its electrophoretic mobility. Atomic force microscopy reveals the average size of 23-kD insulin complexes with PSA of 10–20 nm and demonstrates that more than 60% of glycopolymer molecules carry a single protein molecule. Experiments with cultured cells show that cytokines bound to polysialic acid retain their ability to regulate cell proliferation. Insulin bound to PSA has a prolonged hypoglycemic effect in vivo.     

Synthesis and biological evaluation of N-(arylsulfanyl)carbonyl analogues of paclitaxel (taxol)

Four new N-(arylsufanyl)carbonyl paclitaxel analogues (2a-d) were prepared from 7-(triethylsilyl)-protected baccatin III (5). Their cytotoxicities against human ovarian (A2780) and prostate cancer (PC3) cell lines, as well as their tubulin-assembly activities, were determined. In these assays, the new compounds showed rather weak activities, one two orders of magnitude below those of paclitaxel (taxol; 1). The known 3'-N-[(thiophen-2-yl)carbonyl] paclitaxel analogue 3 was also prepared. As previously reported, 3 exhibited strongly improved cytotoxicities and tubulin-assembly activities as compared to paclitaxel (1).     

Preparation and some properties of a derivative of wheat germ agglutinin with altered biological activity

An inactive derivative of wheat germ agglutinin, which is a strong activator of blood platelets, was prepared by selective chemical modification of the lectin with cyanogen bromide at acid pH. The derivative was then used as a probe to learn about the initial events in platelet stimulation by physiological agents. Amino acid analysis of the modified lectin confirmed specific cleavage of a methionine residue. Gel filtration studies indicated a molecular weight for the lectin derivative similar to the unmodified lectin. In gel electrophoresis in the presence of sodium dodecyl sulfate, reduced samples of the derivative showed two bands and the main component migrated slightly faster than the native lectin. The derivative retained the capacity to precipitate an antibody to the lectin although at least one of the antigenic sites was lost due to chemical modification. The derivative did not compete with the unmodified lectin for binding to platelets. Unlike the parent lectin, the derivative did not aggregate platelets even at a ten fold higher concentration. Under similar conditions, there were about 1.0 X 10(5) binding sites/platelet for the lectin derivative with an apparent dissociation constant of 1.7 microM compared to 5 X 10(5) sites/cell and a dissociation constant of 0.4 microM for the native lectin. Overnight incubation of platelets or red cells with the derivative in microtiter plates showed about 2-5% agglutinating activity for the derivative compared to the unmodified lectin. Incubation of platelets with the lectin derivative inhibited platelet aggregation by thrombin while aggregation induced by a number of other agents was not significantly affected. This inhibitory effect of the lectin derivative on thrombin-induced platelet aggregation could be readily reversed with GlcNAc. The lectin derivative may be a useful tool to explore the structure-function relationship of cell surface components.     

Far ultraviolet optical activity of saccharide derivatives. I. Xylan and cellulose acetates

Optial rotatory dispersion (ORD) and Circular dichroism (CD) spectra of several β-1,4 xylan and cellulose acetates and some of their oligomers were investigated. The CD spectra proved considerably superior in terms of information content and interpretability. Comparison of the xylan and cellulose acetate series which also included partially substited cellulose acetates showed that the sign of the CD of the C(6) acetyl was negative. Likewise, the combined contribution of C(1) and C(4) to their equatorially substituted acetyls was positive (with C(1) definitely Positive) and the combined contribution of C(2)_eq and C(3)_eq negative. The solution conformations of both polysaccharide acetates appeared to be random. The CD of White birch xylan acetate which is substituted on the average at every tenth residue with a 4-O-methyl glucuronic acid substituent, was sensitive to it. The xylan oligomer series also illustrated that CD may be used to determine the degree of polymerization of these oligomers up to about 20.