Carbon-11 N-methyl alkylation of L-368,899 and in vivo PET imaging investigations for neural oxytocin receptors

Compound L-368,899 was successfully alkylated with [¹¹C]iodomethane to generate the oxytocin receptor selective (2R)-2-amino-N-((2S)-7,7-dimethyl-1-(((4-(o-tolyl)piperazin-1-yl)sulfonyl)methyl)bicyclo[2.2.1]heptan-2-yl)-N-[¹¹C]methyl-3-(methylsulfonyl)propanamide ([¹¹C]1) with very high radiochemical purity and high specific activity. PET imaging studies were performed with [¹¹C]1 to investigate brain penetration and oxytocin receptor uptake using rat and cynomolgus monkey models. For rat baseline scans, brain penetration was observed with [¹¹C]1, but no specific uptake could be distinguished in the brain region. By administering a peptide oxytocin receptor selective antagonist for peripheral blocking of oxytocin receptors, the uptake of [¹¹C]1 was amplified in the rat brain temporarily to enable some visual uptake within the rat brain. A baseline scan of [¹¹C]1 in a cynomolgus monkey model resulted in no detectable specific uptake in anticipated regions, but activity did accumulate in the choroid plexus.     

The characterization of a novel V1b antagonist lead series

The SAR around a V1b antagonist HTS hit 3 was explored to produce a series of thiazole sulfonamides as a lead series with selectivity over the related V1 and oxytocin receptors.     

Oxytocin - An Emerging Treatment for Obesity and Dysglycemia: Review of Randomized Controlled Trials and Cohort Studies

Objective: The psychotropic mediator and neuropeptide hormone oxytocin (OXT) is emerging as a promising treatment of metabolic disorders (obesity and dysglycemia). This review focuses on studies relevant to OXT use and its mechanisms of action in metabolic disorders and wellness behavior motivation.Methods: Randomized controlled trials (RCTs) and cohort and preclinical studies identified in electronic databases were reviewed.Results: There were only a few RCTs and cohort studies related to OXT and metabolic disorders. Anorexigenic and weight-loss effects of intranasal OXT (IOXT) were evaluated in 3 double-blind RCTs involving 85 subjects. A single dose of 24 IU reduced caloric intake by 122 kcal. The 24 IU 4-times daily dose for 8 weeks produced ~9-kg weight loss (P<.001 vs. placebo) and a trend toward reduced postprandial glucose and insulin levels. Similarly, in a double-blind RCT IOXT versus placebo increased the willingness to cooperate and the expectation that others will cooperate at prosocial tasks. A cohort study showed lower serum OXT level in obese versus normal-weight subjects and a negative correlation with body mass index. Circulating OXT was also lower in type 2 diabetes versus normoglycemic subjects and negatively correlated with glycosylated hemoglobin A1C and insulin resistance.Conclusion: The gap of knowledge remains on the efficacy of OXT for metabolic indications. It is a challenge to the scientific community to provide data that can be disseminated to inform the scientific community, medical personnel, and the public about the potential benefits and risks of chronic OXT use.Abbreviations:CNS = central nervous systemDM1 = diabetes mellitus type 1DM2 = diabetes mellitus type 2GDM = gestational diabetes mellitusGI = gastrointestinalGMB = gut microbiotaIOXT = intranasal oxytoxcinOXT = oxytocinOXTR = oxytocin receptorsOXT = serum oxytocin     

Identification of a potent and noncytotoxic inhibitor of melanin production

On the basis of a hit from random screening, biaryl amide derivatives were prepared in a combinatorial manner via parallel solution-phase synthesis, and their effects on melanocytes were investigated to discover new effective skin depigmenting agents. Among the 120 derivatives prepared, five members exhibited a >30% reduction of melanin production at 30 μM with a cell viability of >90%. In particular, compound A₃/B₅ exhibited effective inhibitory activity on melanin synthesis. Although the inhibition percentage of A₃/B₅ was slightly lower than that of the positive reference compound, phenylthiourea (PTU), A₃/B₅ demonstrated a much better cell viability than PTU. In vivo evaluation of A₃/B₅ also showed a significant decrease of melanin pigments. In addition, the in silico classification model was built based on the experimental data of library members. Our results suggest that these biaryl amide derivatives may act as potent skin depigmenting agents.     

Synthesis of oxytocin derivatives lipidated via a carbonate or carbamate linkage as a long-acting therapeutic agent for social impairment-like behaviors

In the course of our studies of hydrophobic oxytocin (OT) analogues, we newly synthesized lipidated OT (LOT-4a-c and LOT-5a-c), in which a long alkyl chain (C14-C16) is conjugated via a carbonate or carbamate linkage at the Tyr-2 phenolic hydroxy group and a palmitoyl group at the terminal amino group of Cys-1. These LOTs did not activate OT and vasopressin receptors. Among the LOTs, however, LOT-4c, having a C16-chain via a carbonate linkage at the phenolic hydroxyl group of the Tyr-2, showed very long-lasting action for the recovery of impaired social behavior in CD38 knockout mice, a rodent model of autistic phenotypes, whereas the effect of OT itself rapidly diminished. These results indicate that LOT-4c may serve as a potential prodrug in mice.     

The crystal structure of a nonalkenic,cyclic trimer of levoglucosenone

A single-crystal, X-ray diffraction study was performed on a nonalkenic, cyclic trimer (C₁₈H₁₈O₉, 4) of levoglucosenone, in order to confirm its chemical structure. Crystals of 4 are orthorhombic, with unit-cell parameters of a = 792.20, b = 1874.35, c = 2383.02 pm, space group P2₁2₁2₁, and z = 8. The structure was solved by direct methods, and refined by least-squares to R = 0.032, based on 2990 unique reflections. Each asymmetrical unit contains two symmetry-independent molecules of 4 and one of acetone. The previously assigned chemical structure and stereochemistry of 4 were found to be correct.     

Synthesis and antimalarial evaluation of a screening library based on a tetrahydroanthraquinone natural product scaffold

As part of a research program aimed at discovering new antimalarial leads from Australian macrofungi a unique fungi-derived prefractionated library was screened against a chloroquine-sensitive Plasmodium falciparum line (3D7) using a radiometric growth inhibition assay. A library fraction derived from a Cortinarius species displayed promising antimalarial activity. UV-guided fractionation on the CH₂Cl₂/MeOH extract from this fungus resulted in the isolation of four known compounds: (1S,3R)-austrocortirubin (1), (1S,3S)-austrocortirubin (2), 1-deoxyaustrocortirubin (3), and austrocortinin (4). Compound 2 was used as a natural product scaffold in the parallel solution-phase synthesis of a small library of N-substituted tetrahydroanthraquinones (5–15). All compounds (1–15) were tested in vitro against P. falciparum 3D7 parasites and (1S,3S)-austrocortirubin (2), the major fungal constituent, was shown to be the most active compound with an IC₅₀ of 1.9 μM. This compound displayed moderate cytotoxicity against neonatal foreskin fibroblast (NFF) cells with an IC₅₀ of 15.6 μM.     

Synthesis and SAR studies of novel 2-(4-oxo-2-aryl-quinazolin-3(4H)-yl)acetamide vasopressin V1b receptor antagonists

Synthesis and structure-activity relationships (SAR) of a novel series of vasopressin V_1b (V₃) antagonists are described. 2-(4-Oxo-2-aryl-quinazolin-3(4H)-yl)acetamides have been identified with low nanomolar affinity for the V_1b receptor and good selectivity with respect to related receptors V_1a, V₂ and oxytocin (OT). Optimised compound 12j demonstrates a good pharmacokinetic profile and activity in a mechanistic model of HPA dysfunction.     

Development of a sensitive enzymeimmunoassay for oxytocin determination in bovine plasma

A highly sensitive and specific second antibody enzymeimmunoassay (EIA) on microtiterplates for oxytocin determination in bovine plasma using the biotin–streptavidin amplification system was developed. Biotin was coupled to oxytocin and used to bridge between streptavidin-peroxidase and the immobilized oxytocin antiserum in the competitive assay. The assay was carried out directly in 200 μl of bovine plasma. Oxytocin standards prepared in hormone-free plasma were used. The sensitivity of the assay was 0.25 pg/well which corresponded to 1.25 pg/ml plasma; the 50% relative binding was seen at 2.8 pg/well. Plasma volumes for the assay ranging from 50 to 200 μl did not influence the shape of the oxytocin standard curve; however a distinct drop in the OD₄₅₀ was observed with higher plasma volumes. The oxytocin antiserum used in the assay showed no significant cross-reaction with other octapeptides tested. The assay was compared with a radioimmunoassay (RIA) procedure employing prior solvent extraction of plasma samples. The oxytocin concentrations assayed by EIA and RIA in plasma samples obtained from four cows before, during and after milking were highly correlated and very similar (r=0.97). Hence the assay developed offers an attractive alternative to the RIA since no prior laborious plasma extraction is needed. Further, the assay has the distinct advantage of being non-radioactive in nature.     

Fluoroboration of a Schiff-base ligand through nickel tetrafluoroborate

The nickel-assisted equilibrium-fluoroboration of the Schiff-base compound, a 2-pyridinecarboxaldehyde salicylhydrazone (H₂L) is reported. Crystal structure of the fluoroborated nickel compound 1 Ni(L-BF₂)₂ revealed that the boron atom was in a distorted tetrahedral geometry with two of the fluorine atoms, one of the phenol oxygen atom and the uncoordinated hydrazone nitrogen atom occupying the four coordination positions. It was suggested that the coordination abilities of the precursor H₂L and the product L-BF₂ to the nickel atom are important factors influencing the fluoroboration. The cobalt and nickel compounds Co(HL)₂ (2) and Ni(HL)₂ (3) of the precursor ligand were also structurally characterized for comparison. The ESI-MS spectra revealed that both sodium and cobalt tetrafluoroborate salt cannot make the precursor fluoroborated, and the fluoroboration of the precursor occurred only in the presence of nickel ion.     

Functional nickel thiosalen complexes: structure and solid-state packing of a transition metal-based surfactant

The complex NiBr₂(2-C₁₂H₂₅SC₆H₄CHNCH₂CH₂NCHC₆H₄SC₁₂H₂₅-2) (1) was prepared from the ligand 2-C₁₂H₂₅SC₆H₄CHNCH₂CH₂NCHC₆H₄SC₁₂H₂₅-2 (3) and NiBr₂. Paramagnetic 1 was characterized by combustion analyses, ¹H and ¹³C NMR spectroscopy, Vis–NIR spectroscopy, measurement of its magnetic susceptibility, and single-crystal X-ray diffraction. The crystal structure of 1 features octahedral coordination of Ni(II) with axial bromides and fully extended interdigitated alkyl chains. There are significant differences between the solid state structures of 1 and NiBr₂(2-C₆H₁₂SC₆H₄CHNCH₂CH₂NCHC₆H₄SC₆H₁₂-2) (2), a previously reported homologue.     

Acidic biphenyl derivatives: Synthesis and biological activity of a new series of potent 5-HT4 receptor antagonists

Serotonin (5-hydroxytryptamine, 5-HT) is an important signaling molecule in the central nervous system (CNS) and in non-neuronal tissues and organs. Serotonin mediates a positive chronotropic and inotropic response through 5-HT₄ receptors in the atrium and ventricle of the heart. Recent investigations have revealed increased expression of the 5-HT_4(b) isoform in cardiomyocytes of chronic arrhythmic and failing hearts, and that the use of 5-HT₄ receptor antagonists may be beneficial for treating these conditions. The 5-HT₄ receptor possesses a transmembrane (TM) binding site important for ligand affinity and recognition, as well as a capacity to accommodate bulky ligands. A new series of peripherally-acting 5-HT₄ receptor antagonists were prepared by combining the acidic biphenyl group from the class of angiotensin II receptor blockers (ARBs) with the SB207266 (piboserod) scaffold. The new compounds were pharmacologically evaluated and carboxylic acid 21 was identified as a potent and promising 5-HT₄ receptor antagonist with moderate affinity for the AT₁ receptor. The permeability of carboxylic acid 21 in a Caco-2 assay was low and the corresponding prodrug esters 23a–f were therefore prepared. The pharmacokinetics of methyl ester 20 and n-butyl ester 23c were evaluated in a rat model, revealing incomplete metabolism to carboxylic acid 21. However, methyl ester 20 is a potent 5-HT₄ receptor antagonist with binding affinities in the low picomolar range. Methyl ester 20 has promising oral bioavailability and pharmacokinetics and may target 5-HT₄ receptors in both CNS and peripheral organs.     

Exploration of a potential difluoromethyl-nucleoside substrate with the fluorinase enzyme

The investigation of a difluoromethyl-bearing nucleoside with the fluorinase enzyme is described. 5′,5′-Difluoro-5′-deoxyadenosine 7 (F₂DA) was synthesised from adenosine, and found to bind to the fluorinase enzyme by isothermal titration calorimetry with similar affinity compared to 5′-fluoro-5′-deoxyadenosine 2 (FDA), the natural product of the enzymatic reaction. F₂DA 7 was found, however, not to undergo the enzyme catalysed reaction with l-selenomethionine, unlike FDA 2, which undergoes reaction with l-selenomethionine to generate Se-adenosylselenomethionine. A co-crystal structure of the fluorinase and F₂DA 7 and tartrate was solved to 1.8 Å, and revealed that the difluoromethyl group bridges interactions known to be essential for activation of the single fluorine in FDA 2. An unusual hydrogen bonding interaction between the hydrogen of the difluoromethyl group and one of the hydroxyl oxygens of the tartrate ligand was also observed. The bridging interactions, coupled with the inherently stronger C–F bond in the difluoromethyl group, offers an explanation for why no reaction is observed.     

Reactivity of a low-valent chromium dinitrogen complex

(Nn^iPrCr)₂(μ₂-κ²:κ²-N₂) (1, Nn^iPr = bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato), formally a chromium(I) complex, was exposed to a variety of small molecules possessing hetero- or homo-atomic single, double, or triple bonds. Reaction of 1 with adamantyl azide yielded complexes in various higher oxidation states, such as (Nn^iPrCr^II)₂(μ₂-NAd) (2), Nn^iPrCr^III(κ²-N₄Ad₂) (3), or Nn^iPrCr^V(NAd)₂ (4). Compound 1 was found to reductively couple 3-pentanone to form Nn^iPrCr(κ²-O₂C₂Et₄) (5) and reductively couple benzylidene aniline to form both Nn^iPrCr^III(cis-κ²-C₂₈H₂₂N₂) (6a) an Nn^iPrCr^III(trans-κ²-C₂₈H₂₂N₂) (6b). Reaction with a stochiometric amount of benzylidene aniline yielded the imine complex Nn^iPrCr(η²-NPhCHPh) (7). Exposure of 1 to a bulky isocyanide formed the octahedral Nn^iPrCr^I[CN(C₆H₄(Me)₂]₄ (9). Complex 1 was also found to break the O-O, NO, and S-S bonds in various small molecules to form Nn^iPrCr^II(OCMe₃) (11), Nn^iPrCr^V(O)(NPh) (8), and [Nn^iPrCr^II(μ-SPh)]₂ (10).     

Two new coumarins and a new xanthone from the leaves of Rhizophora mucronata

Two new coumarins (1, 2) and a new xanthone (3), together with 14 known compounds—eight coumarins (4, 5, 9, 10, 12–15), three xanthones (11, 16, 17), a benzoic acid (6) and two flavonones (7, 8)—were isolated from the leaves of Rhizophora mucronata. The structures of the compounds were elucidated by spectroscopic (IR, MS, and NMR) analyses. The isolated compounds were tested for cytotoxicity against human cancer cell lines HL-60 and HeLa. Among these compounds, only compound 16 inhibited the growth of both HeLa (IC₅₀?=?4.8?μM) and HL-60 (IC₅₀?=?1.0?μM) cells. Compounds 4, 7, 10, and 12 exhibited moderate activity against HeLa cells (IC₅₀?=?3.8–8.3?μM). Compounds 5, 9, 11, and 17 showed moderate activity against HL-60 cells (IC₅₀?=?2.2–6.3?μM). Higher selectivity against HL-60 cell lines was observed for compounds 5, 9, 11, and 16 with SI values (NIH 3T3/HL-60) of 8.6, 19.2, 9.4, and 10.2, respectively.     

Aureolic acids from a marine-derived Streptomyces sp. WBF16

A marine-derived actinomycete (Streptomyces sp. WBF16) exhibiting antitumor activities was investigated. The strain was identified using morphological, biochemical and genetic techniques. 16S rDNA sequence of the isolate indicated that it was most closely related to Streptomyces coelicolor A3 (2). Furthermore, a new aureolic acid (Chromomycin B, 1), along with Chromomycin A₂ (2) and Chromomycin A₃ (3) were isolated from its secondary metabolites. Their structures were determined by chemical and spectroscopic methods including 1D, 2D NMR and HRMS. Compounds 1–3 showed strong cytotoxicity against SGC7901, HepG2, A549, HCT116 and COC1 and HUVEC.     

Discovery of a novel series of hDHODH inhibitors with anti-pulmonary fibrotic activities

Human dihydroorotate dehydrogenase (hDHODH) is a flavin-dependent enzyme essential to pyrimidine de novo biosynthesis, which serves as an attractive therapeutic target for the treatment of autoimmune disorders. A novel series of hDHODH inhibitors was developed based on a lead which was obtained by a medicinal chemistry exploration. Most compounds showed moderate to significant potency against hDHODH, compounds 5d, 5e, and 6a effectively inhibited the activities of hDHODH with IC₅₀ values from 0.9 to 2.8 μM. Further studies showed that compound 5e also effectively suppressed proliferation of the activated PBMCs (IC₅₀ = 20.35 μM). Surprisingly, compound 5e also showed anti-pulmonary fibrotic activity similar to that of pirfenidone in vitro assay. Therefore, compound 5e might have potential to be developed as a novel hDHODH inhibitors for autoimmune diseases therapy.     

Identification of HUHS190, a human naftopidil metabolite,as a novel anti-bladder cancer drug

We carried out structure-activity relationship study on anti-cancer effects of naftopidil (1) and its metabolites, resulted in identification of 1-(4-hydroxy-2-methoxyphenyl)piperazin-1-yl)-3-(naphthalen-1-yloxy) propan-2-ol (2, HUHS190), a major human metabolite of 1, which exhibited the most selective toxicities between against normal and cancer cells (Table 1). 2 was more hydrophilic compared to 1, was enough to be prepared in high concentration solution of more than 100 μM in saline for an intravesical instillation drug. Moreover, serum concentration of 2 was comparable to that of 1, an oral preparation drug, after oral administration at 32 mg/kg (Fig. 3). Both of 1 and 2 showed broad-spectrum anti-cancer activities in vitro, for example, 1 and 2 showed inhibitory activity IC₅₀ = 21.1 μM and 17.2 μM for DU145, human prostate cancer cells, respectively, and IC₅₀ = 18.5 μM and 10.5 μM for T24 cells, human bladder cancer cells. In this study, we estimated anticancer effects of 2 in a bladder cancer model after intravesical administration similar to clinical cases. A single intravesical administration of 2 exhibited the most potent inhibitory activities among the clinical drugs for bladder cancers, BCG and Pirarubicin, without obvious side effects and toxicity (Fig. 4). Thus, HUHS190 (2) can be effective for patients after post-TURBT therapy of bladder cancer without side effects, unlike the currently available clinical drugs.     

Design and synthesis of a new steroid-macrocyclic derivative with biological activity

The aims of this study were to evaluate the positive inotropic effect of a new macrocyclic derivative (compound 11) and characterize the molecular mechanism involved in its biological activity. The first step was achieved by synthesis of a macrocyclic derivative involving a series of reactions for the preparation of several steroid derivatives such as (a) steroid-pyrimidinone (3 and 4), (b) steroid-amino (5), (c) steroid-imino (6), (d) ester-steroid (7 and 8), and (e) amido-steroid (9 and 10). Finally, 11 was prepared by removing the tert-butyldimethylsilane fragment of 10. The biological activity of compounds on perfusion pressure and vascular resistance was evaluated on isolated rat heart using the Langendorff model. The inotropic activity of 11 was evaluated in presence of prazosin, metoprolol, indomethacin, nifedipine, and flutamide to characterize its molecular mechanism. Theoretical experiments were carried out with a Docking model, to assess potential interactions of androgen receptor with 11. The results showed that only this macrocyclic derivative exerts changes on perfusion pressure and vascular resistance translated as the positive inotropic effect, and this effect was blocked with flutamide; these data indicate that the positive inotropic activity induced by this macrocyclic derivative was via androgen receptor activation. The theoretical results indicated that the interaction of the macrocyclic derivative with the androgen receptor involves several amino acid residues such as Leu₇₀₄, Asn₇₀₅, Met₇₈₀, Cys₇₈₄, Met₇₄₉, Leu₇₆₂, Phe₇₆₄, Ser₇₇₈, and Met₇₈₇. In conclusion, all these data suggest that the positive inotropic activity of the macrocyclic derivative may depend on its chemical structure.     

Osthenol,a prenylated coumarin,as a monoamine oxidase A inhibitor with high selectivity

Osthenol (6), a prenylated coumarin isolated from the dried roots of Angelica pubescens, potently and selectively inhibited recombinant human monoamine oxidase-A (hMAO-A) with an IC₅₀ value of 0.74?µM and showed a high selectivity index (SI?>?81.1) for hMAO-A versus hMAO-B. Compound 6 was a reversible competitive hMAO-A inhibitor (K_i?=?0.26?µM) with a potency greater than toloxatone (IC₅₀?=?0.93?µM), a marketed drug. Isopsoralen (3) and bakuchicin (1), furanocoumarin derivatives isolated from Psoralea corylifolia L., showed slightly higher IC₅₀ values (0.88 and 1.78?µM, respectively) for hMAO-A than 6, but had low SI values (3.1 for both). Other coumarins tested did not effectively inhibit hMAO-A or hMAO-B. A structural comparison suggested that the 8-(3,3-dimethylallyl) group of 6 increased its inhibitory activity against hMAO-A compared with the 6-methoxy group of scopoletin (4). Molecular docking simulations revealed that the binding affinity of 6 for hMAO-A (?8.5?kcal/mol) was greater than that for hMAO-B (?5.6?kcal/mol) and that of 4 for hMAO-A (?7.3?kcal/mol). Docking simulations also implied that 6 interacted with hMAO-A at Phe208 and with hMAO-B at Ile199 by carbon hydrogen bondings. Our findings suggest that osthenol, derived from natural products, is a selective and potent reversible inhibitor of MAO-A, and can be regarded a potential lead compound for the design of novel reversible MAO-A inhibitors.