Effect of luteinizing hormone releasing hormone analogues on testosterone metabolismin vitro — A study with mature rat ventral prostates

The effects of two luteinizing hormone releasing hormone analogues (a superagonist and an antagonist) on the conversion of testosterone to dihydrotestosterone in homogenates prepared from adult rat ventral prostates were studied. At higher doses, the superagonist showed a significant dose-dependent inhibition of the conversion of testosterone to dihydrotestosterone. In comparison, the antagonist showed only a marginally inhibitory trend. The implications of these observed effects vis-a-vis the use of the analogues in the endocrine management of prostatic cancer have been discussed.     

The relationship between micelle formation and biological activity of peptide 562–572 of luteinizing hormone receptor modified with decanoyl radicals

Lipophilic derivatives of peptides corresponding to cytoplasmic regions of G protein-coupled receptors (GPCR) can act as intracellular agonists. Our previous work showed that peptides corresponding to residues 562–572 of luteinizing hormone receptor and modified with palmitate or decanoate at the C-terminus activate adenylate cyclase in rat testes. The stimulating effect of peptide 562–572 modified with decanoates at both the N- and the C-termini (peptide IV) reached its maximum at the peptide concentration of 10^–5 M and diminished with further increase in its concentration. It was supposed that this effect was due to peptide IV ability to form micelles. To verify this hypothesis, the relationship between biological activity, hydrophobicity, and ability to form micelles was investigated for peptide IV and other acylated derivatives of peptide 562–572, including those carrying C-terminal decanoate (peptide III) and palmitate (peptide VI) moieties. It was found that the stimulating effect of peptide IV taken in the concentration of 10^–5 M on adenylate cyclase activity in plasma membranes of rat testes and ovaries was only slightly lower than that of peptide VI and higher than the effect of peptide III. At the concentration of 10^–3 M, the effect of peptide IV was 20–27% lower and amounted to only 50–51 and 87–88% of the effects of peptides VI and III, respectively. In spite of its high hydrophobicity, peptide IV was characterized with an abnormally low retention time when eluted from a Nucleosil C8 column during reverse-phase HPLC: it was even lower than the retention time of nonmodified peptide 562–572. However, the retention time of peptide IV, but not of other peptides, increased significantly when the eluent contained a higher proportion of trifluoroacetic acid, which disrupts micellelike structures (0.5 instead of 0.1%). The surface tension of peptide IV solution in water slightly decreased with increasing peptide concentration, but rapidly dropped and reached a plateau at the concentration of 7 × 10^–6 M, which indicates the beginning of micelle formation. Thus, peptide IV in the concentrations above 10^–5 M forms micelles, which prevents it from interacting with the receptor. The ability of GPCR peptides to aggregate and form micelles should be taken into account in the development of their new membrane-active analogs.     

Synthesis,structure–activity relationships and biological evaluation of barbigerone analogues as anti-proliferative and anti-angiogenesis agents

A series of barbigerone analogues (7a–7w, 13a–13x) were designed, synthesized and biologically evaluated for their anti-proliferative and anti-angiogenic activities. Among these compounds, compound 13a exhibited the most potent inhibitory effect on the proliferation of HUVECs, HepG2, A375, U251, B16, and HCT116 cells (IC₅₀ = 3.80, 0.28, 1.58, 3.50, 1.09 and 0.68 μM, respectively). Compound 13a inhibited the angiogenesis in zebrafish embryo assay in a concentration-dependent manner. Furthermore, 13a also effectively inhibited the migration and capillary like tube formation of human umbilical vein endothelial cell in vitro. These results support the further investigation of this class of compounds as potential anti-proliferative and anti-angiogenesis agents.     

Synthesis and biological activity of ester and ether analogues of α-galactosylceramide (KRN7000)

α-Galactosylceramide (αGalCer, KRN7000) has been identified as a modulator of immunological processes through its capacity to bind iNKT cells mediated by CD1d molecules. Some analogues in while the amide group in αGalCer is replaced with ester or ether groups were synthesized from d-arabinitol or l-ribose to evaluate their ability to activate iNKT cells. Ester analogues 30a, 31a, and 61 showed activity for IFNγ and IL-4 production of iNKT cells, while ether (31b) and 4-methoxy ester (76) analogues of α-galactosylceramide were not active for iNKT cells.     

Synthesis and biological evaluation of tyrosine modified analogues of the α4β7 integrin inhibitor biotin-R(8)ERY

The α4β7 integrin is a well-known target for the development of drugs against various inflammatory disease states including inflammatory bowel disease, type 1 diabetes and multiple sclerosis. The synthesis of a small library of cell-permeable β7 integrin inhibitors based on the peptide biotin-R(8)ERY is reported, in which the tyrosine residue has been modified by using the Suzuki-Miyaura cross-coupling reaction. The synthesised peptidomimetics were evaluated in a cell adhesion assay and shown to inhibit Mn(2+)-activated adhesion of mouse TK-1 T cells to mouse MAdCAM-1. All of the synthesised peptidomimetics are more active than our previously reported lead compound biotin-R(8)ERY with two of the analogues, 6 and 7, exhibiting IC(50) values of <15μM.     

Synthesis and reactivity of novel γ-phosphate modified ATP analogues

We hereby present a simple yet novel chemical synthesis of a family of γ-modified ATPs bearing functional groups on the γ-phosphate that are amenable to further derivatization by highly selective chemical manipulations (e.g., click chemistry, Staudinger ligations). A preliminary screen of these compounds as phosphate donors with a typical wild type protein kinase (cdk2) and one of its known substrates p27^kip1 is also presented.     

Synthesis and biological activities of amino acids functionalized α-GalCer analogues

Invariant natural killer T-cells (iNKT-cells) are promising targets for manipulating the immune system, which can rapidly release a large amount of Th1 and Th2 cytokines upon the engagement of their T cell receptor with glycolipid antigens presented by CD1d. In this paper, we wish to report a novel series of α-GalCer analogues which were synthesized by incorporation of l-amino acid methyl esters in the C-6′ position of glycolipid. The evaluation of these synthetic analogues for their capacities to stimulate iNKT-cells into producing Th1 and Th2 cytokines both in vitro and in vivo indicated that they were potent CD1d ligands and could stimulate murine spleen cells into a higher release of the Th1 cytokine IFN-γ in vitro. In vivo, Gly-α-GalCer (1) and Lys-α-GalCer (3) showed more Th1-biased responses than α-GalCer, especially analogue 3 showed the highest selectivity for IFN-γ production (IFN-γ/IL-4 = 5.32) compared with α-GalCer (IFN-γ/IL-4 = 2.5) in vivo. These novel α-GalCer analogues might be used as efficient X-ray crystallographic probes to reveal the relationship between glycolipids and CD1d proteins in α-GalCer/CD1d complexes and pave the way for developing new potent immunostimulating agents.     

Synthesis and anticancer activity of novel quinoline–docetaxel analogues

A series of novel quinoline–docetaxel analogues (6a–6g, 13a–13g) were designed and synthesized by introducing bioactive quinoline scaffold to C2′-OH of docetaxel. The anticancer activities of these novel analogues were investigated against different human cancer cell lines including Hela, A549, A2780, MCF-7 and two resistant strains A2780-MDR and MCF-7-MDR. The data showed these analogues possessed similar to better cytotoxicity than docetaxel. Compound 6c was found to be the most potent one, and its IC₅₀ value against MCF-7-MDR was 8.8 nM (IC₅₀ of docetaxel was 180 nM). The work indicated that the introduction of quinolyl group in docetaxel could enhance cytotoxicity and reduce drug-resistance.     

Synthesis and structure–activity relationships of fibrate-based analogues inside PPARs

In an effort to develop safe and efficacious compounds for the treatment of metabolic disorders, new compounds based on a combination of clofibric acid, the active metabolite of clofibrate, and lipophilic groups derived from natural products chalcone and stilbene were synthesised. Some of them were found to be active at micromolar concentrations only on PPARα or PPARγ, while others were identified as dual agonists PPARα/γ.     

Synthesis and structure–activity relationship of substitutions at the C-1 position of Δ9-tetrahydrocannabinol

A novel series of Δ9-tetrahydrocannabinol (Δ9-THC) analogues were synthesized to determine their potential as cannabinoid receptor modulators. Chemistry focused on conversion of the phenol of Δ9-THC to other functionality through palladium catalyzed reactions with an intermediate triflate 2. Two analogues with sub 100 nM affinity for the CB₁ and CB₂ receptors were identified.     

Synthesis,biological activity and structure–activity relationship of endomorphin-1/substance P derivatives

Endomorphins have been shown to produce potent analgesia in various rodent models of pain. However, their central administration led to the development of tolerance and physical dependence. Conjugation of C-terminal substance P (SP) fragments to opioids and opioid peptides was previously shown to produce hybrid peptides with strong analgesic activity, with low or no propensity to develop tolerance. In this study, four peptides (2–5) comprised of endomorphin-1 (1) and C-terminal fragments of SP (four or five amino acids, SP_8–11 (2) or SP_7–11 (4), respectively), with an overlapping Phe residue, were synthesized. To overcome low metabolic stability and poor membrane permeability of the peptide, the N-terminus of 2 and 4 was further modified with a C10-carbon lipoamino acid (C10LAA) achieving 3 and 5, respectively. LAA-modification of the hybrid peptides resulted in a significant increase in metabolic stability and membrane permeability compared to peptides 1, 2 and 4. Compound 5 showed potent μ-opioid receptor binding affinity (K_iμ = 3.87 ± 0.51 nM) with dose-dependent agonist activity in the nanomolar range (IC₅₀ = 45 ± 13 nM). In silico modeling was used to investigate the binding modes and affinities of compounds 1–5 in the active site of μ-opioid receptors. The docking scores were in agreement with the K_iμ values obtained in the receptor binding affinity studies. The more active LAA-modified hybrid peptide showed a lower total interaction energy and higher negative value of MolDock score.     

Lipase-catalyzed preparation of chromomycin A₃ analogues and biological evaluation for anticancer activity

Several acyl derivatives of the aureolic acid chromomycin A(3) were obtained via lipase-catalyzed acylation. Lipase B from Candida antarctica (CAL-B) was found to be the only active biocatalyst, directing the acylation regioselectively towards the terminal secondary hydroxyl group of the aglycone side chain. All new chromomycin A(3) derivatives showed antitumor activity at the micromolar or lower level concentration. Particularly, chromomycin A(3) 4'-vinyladipate showed 3-5 times higher activity against the four tumor cell lines assayed as compared to chromomycin A(3).     

Synthesis,antioxidant capacity,and structure–activity relationships of tri-O-methylnorbergenin analogues on tyrosinase inhibition

A series of tri-O-methylnorbergenin analogues 1–9 were synthesized and their antioxidant activities and inhibitory effects on tyrosinase were evaluated. Among tested analogues, compound 4 bearing cathechol moiety exhibited greater antioxidant activity and excellent inhibition on tyrosinase with IC₅₀ value of 9.1 μM, comparable to that of corresponding positive controls. The inhibition mechanism analysis of compound 4 demonstrated that it was a mixed-type inhibitor on tyrosinase. These results suggest that these compounds may serve as a useful clue for further designing and development of novel potential tyrosinase inhibitors.     

Alteration in the normal pattern of serum testosterone and 5α-androstane-3α,17β-diol in the immature male rat following chronic treatment with luteinizing hormone releasing hormone or luteinizing hormone

A major component of sexual maturation in the male rat is a progressive decline in serum concentrations of 5α-androstane-3α,17β-diol (3α-diol) and a concomitant increase in testicular testosterone biosynthesis and secretion. Chronic administration of synthetic luteinizing hormone releasing hormone (LHRH) or luteinizing hormone (LH)/human chorionic gonadotropin (hCG) to immature male rats has been shown to result in a delay in sexual maturation as evidenced by decreased sex accessory gland weights and altered testicular testosterone production. We have examined the postulate that such treatments may either reverse or retard the normal developmental pattern of serum testosterone and 3α-diol concentrations. Chronic $\text{in vivo}$ treatment of 28 day old immature male rats for 2 weeks with daily injections of either 0.5 μg of LHRH, 1.0 μg of LHRH, or 30 μg of LH was found to result in significant reductions in weights of the seminal vesicles and ventral prostate glands and diminutions in serum testosterone concentrations. Serum content of 3α-diol was either unchanged or slightly elevated in the LHRH treated animals and increased significantly in the LH treated animals. These data suggest that either a reversal of or retardation in the normal developmental pattern of serum testosterone and 3α-diol content has been achieved in the immature male rat by chronic LHRH or LH treatment.     

Synthesis and biological activity of aryl S-β-glycosides of 1-thio-N-acetylmuramyl-L-alanyl-D-isoglutamine

Phenyl, p-tolyl, and p-tert-butylphenyl β-1-thio-N-acetylglucosaminides were synthesized by the treatment of thiophenols with peracetate of α-D-glucosaminyl chloride in the presence of triethylamine or under the conditions of phase-transfer catalysis with quaternary ammonium salts. The compounds synthesized were used for obtaining of glycosides of 4,6-O-isopropylidene-N-acetylmuramic acid, which were coupled with L-Ala-D-Glu(NH₂)-OBzl and then deprotected to obtain the target aryl β-thioglycosides of N-acetylmuramyl-L-analyl-D-isoglutamine (MDP). The aryl β-thioglycosides of MDP were found to stimulate an antibacterial resistance toward Staphylococcus aureus in mice. The reliable induction of the spontaneous activity of natural killers in the population of blood mononuclear cells was observed only for phenyl β-thio-MDP at a dose of 200 μg/ml. Original Russian Text ? A.E. Zemlyakov, V.N. Tsikalova, L.R. Azizova, V.Ya. Chirva, E.L. Mulik, M.V. Shkalev, O.V. Kalyuzhin, M.V. Kiselevsky, 2008, published in Bioorganicheskaya Khimiya, 2008, Vol. 34, No. 2, pp. 245–251.     

Synthesis and structure–activity relationship studies of cytotoxic vinorelbine amide analogues

A series of 3-demethoxycarbonyl-3-acylamide methyl vinorelbine derivatives (compounds 7a–7z) were designed, synthesized, and evaluated for their inhibition activities against human non-small cell lung cancer cell line (A549). Most of the amide derivatives exhibited potent cytotoxicity, with the size of the introduced substituents being the foremost factor in determining the resultant cytotoxic activity. Test results in vivo against nude mice bearing A549 xenografts indicated that 7y showed comparable activities compared to the parent NVB.     

Novel analogues of Istaroxime,a potent inhibitor of Na+,K+-ATPase: Synthesis,structure–activity relationship and 3D-quantitative structure–activity relationship of derivatives at position 6 on the androstane scaffold

We report the synthesis and biological properties of novel analogues of Istaroxime acting as positive inotropic compounds through the inhibition of the Na⁺,K⁺-ATPase. We explored the chemical space around the position 6 of the steroidal scaffold by changing the functional groups at that position and maintaining a basic oximic chain in position 3. Some compounds showed inhibitory potencies of the Na⁺,K⁺-ATPase higher than Istaroxime and many of the compounds tested in vivo were safer than digoxin, the classic digitalis compound currently used for the treatment of congestive heart failure as inotropic agent. The 3D-QSAR analyses using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods have been successfully applied to a set of 63 androstane derivatives as Na⁺,K⁺-ATPase inhibitors. The contour plots provide many useful insights into relationships between structural features and inhibitory potency.     

Synthesis,protonation constants and biological activity determination of amino acid–salicylaldehyde-derived Schiff bases

Schiff bases represent a class of molecules widely studied for their importance in organic and coordination chemistry. Despite the large amount of studies on the chemical and biological properties of the Schiff bases, the different experimental conditions prevent a useful comparison to search for a correlation structure–activity. Moreover, literature is lacking in comprehensive data on the spectroscopic characterization of these compounds. For this reason, six Schiff bases, derived from salicylaldehyde and natural amino acids were fully characterized by nuclear magnetic resonance and infrared spectroscopy, and their aqueous solution equilibria, antiproliferative activity and DNA-binding activity were examined. All experimental conditions were kept constants to achieve comparable information and useful insights about their structure–activity correlation. The synthesized compounds showed DNA binding constants in the 10¹–10² M⁻¹ range, depending on the substituent present in the amino acid side-chain, and resulted devoid of significant cytotoxic activity against the different human tumor cell lines showing IC50 values higher than 100 µM.

     

Synthesis and biological evaluation of Esaprazole analogues showing σ1 binding and neuroprotective properties in vitro

Esaprazole, a molecule previously acknowledged to protect against stomach and intestinal ulcers was surprisingly discovered to have neuroprotective activities and σ₁ binding in vitro. A highly diverse set of Esaprazole analogues 2–5 was prepared in order to increase blood–brain barrier penetration. The analogues showed a structure–activity relationship at the σ₁ receptor closely matching already published pharmacophores. Many of the analogues were shown to have neuroprotective properties in two assays using primary cultures of cortical neurons exposed to glutamate and hydrogen peroxide. However, no apparent SAR for these two assays could be developed. Metabolic stability of the analogues were also investigated and the structure of R¹ had a significant bearing on the ADME properties of the compound resulting in two series of compounds. Compounds in which R¹ was a H or acyl group had good metabolic stability in RLM but poor BBB penetration, whereas compounds where R¹ was a cyclo- or bicyclo-alkyl group had poor metabolic stability but good BBB penetration.