N-Iodosaccharin-pyridine co-crystal system under pressure: experimental evidence of reversible twinning

This work presents a single-crystal X-ray diffraction study of an organic co-crystal composed of N-iodosaccharin and pyridine (NISac·py) under hydrostatic pressure ranging from 0.00 (5) GPa to 4.5 (2) GPa. NISac·py crystallizes in the monoclinic system (space group B2₁/e). The unconventional setting of the space group is adopted (the conventional setting is P2₁/c, No. 14) to emphasise the strongly pseudo-orthorhombic symmetry of the lattice, with a β angle very close to 90°. The crystal structure contains one molecule each of N-iodosaccharin (NISac) and pyridine (py) in the asymmetric unit (Z' = 1), linked via an N_sac...I...N'_py halogen-bonding motif. A gradual modification of this motif is observed under pressure as a result of changes in the crystalline environment. Mechanical twinning is observed under compression and the sample splits into two domains, spanning an unequal volume that is mapped by a twofold rotation about the [100] direction of the B2₁/e unit cell. The twinning is particularly significant at high pressure, being reversible when the pressure is released. The structure of the twinned sample reveals the continuity of a substantial substructure across the composition plane. The presence of this common substructure in the two orientations of the twinned individuals can be interpreted as a structural reason for the formation of the twin and is the first observed example in a molecular crystal. These results indicate that the anisotropy of intermolecular interactions in the crystal structure results in an anisotropic strain generated upon the action of hydrostatic compression. Periodic density functional theory calculations were carried out by considering an isotropic external pressure, the results showing good agreement with the experimental findings. The bulk modulus of the crystal was obtained from the equations of state, being 7 (1) GPa for experimental data and 6.8 (5) GPa for theoretical data.

Anticancer effect of a novel palladium-saccharinate complex of terpyridine by inducing apoptosis on Ehrlich ascites carcinoma (EAC) in Balb-C mice

BACKGROUND/AIM

[Pd(sac)(terpy)](sac)•4H2O (sac=saccharinate and terpy=2,2':6',2"-terpyridine) is newly-synthesized palladium(II) (Pd) complex. We investigated the antiproliferative and apoptotic effects of this complex on Ehrlich ascites carcinoma (EAC).

MATERIALS AND METHODS

EAC cells were administered to 33 Balb/c mice. Mice were divided randomly into four groups: control, cisplatin, Pd(II) complex and paclitaxel. Control group animals received 0.9% NaCl; other groups received treatments cisplatin, Pd(II) complex and paclitaxel on days 7 and 12. At day 14, animals were sacrificed. Expression of active caspase-3, p53 and proliferating cell nuclear antigen (PCNA) was investigated and apoptosis was evaluated by terminal deoxynucleotidyltransferase (TdT)-mediated nick-end labelling (TUNEL) technique.

RESULTS

Expression of p53 and PCNA were found to be decreased (p<0.0001), cells with active caspase-3 and TUNEL-positive cells were found to be increased (p<0.0001) in all treatment groups.

CONCLUSION

Like cisplatin and paclitaxel, this Pd(II) complex has a strong anticancer activity against EAC by inducing apoptosis and suppressing proliferation in vivo.

Synthesis, crystal structure, spectroscopic, fluorescent, thermal properties and EPR spectra of doped Cu2+ ions in [Cd(sac)2(H2O)2(meim)2] single crystal

The crystal structures of the six-coordinate complexes [Cd(sac)2(H2O)2(meim)2] (complex 1) formed by reaction of 4-methylimidazole(meim) with [Cd(sac)2(H2O)4]·2H2O (saccharinate=sac), was synthesized and characterized by elemental analysis, infrared (IR) and electron paramagnetic resonance (EPR) spectroscopy, thermal analysis and X-ray single crystal diffraction. X-ray diffraction analysis revealed that complex 1 crystallized in the monoclinic crystal system with space group P21/c. The Cd(II) center was six-coordinated with four nitrogen atoms from two sac and two 4-meim ligands, two oxygen atoms from two aqua ligands. Spectral and thermal analysis data for complex 1 was in agreement with the crystal structures. In addition complex 1 displayed blue fluorescent emission in the solid state at room temperature. Single crystal EPR spectra at room temperature are resolved and have exhibited that two different Cu(2+) complexes were located in different chemical environments which contained two magnetically nonequivalent Cu(2+) sites. In low temperature EPR spectra down to 110 °C did show no considerable change. At higher temperatures, however, both thermo gravimetric analyses (TGA) and EPR spectra showed detectable changes around 140 °C; the causes and the mechanisms of changes are discussed.

A new family of covalent inhibitors block nucleotide binding to the active site of pyruvate kinase

PYK (pyruvate kinase) plays a central role in the metabolism of many organisms and cell types, but the elucidation of the details of its function in a systems biology context has been hampered by the lack of specific high-affinity small-molecule inhibitors. High-throughput screening has been used to identify a family of saccharin derivatives which inhibit LmPYK (Leishmania mexicana PYK) activity in a time- (and dose-) dependent manner, a characteristic of irreversible inhibition. The crystal structure of DBS {4-[(1,1-dioxo-1,2-benzothiazol-3-yl)sulfanyl]benzoic acid} complexed with LmPYK shows that the saccharin moiety reacts with an active-site lysine residue (Lys335), forming a covalent bond and sterically hindering the binding of ADP/ATP. Mutation of the lysine residue to an arginine residue eliminated the effect of the inhibitor molecule, providing confirmation of the proposed inhibitor mechanism. This lysine residue is conserved in the active sites of the four human PYK isoenzymes, which were also found to be irreversibly inhibited by DBS. X-ray structures of PYK isoforms show structural differences at the DBS-binding pocket, and this covalent inhibitor of PYK provides a chemical scaffold for the design of new families of potentially isoform-specific irreversible inhibitors.

CLM94, a novel cyclic amide with anti-VEGFR-2 and antiangiogenic properties, is active against primary anaplastic thyroid cancer in vitro and in vivo

CONTEXT AND OBJECTIVE

We have studied the antitumor activity of a novel cyclic amide, CLM94, with anti-vascular endothelial growth factor (VEGF) receptor-2 and antiangiogenic activity in primary anaplastic thyroid cancer (ATC) cells in vitro and in vivo.

DESIGN AND MAIN OUTCOME MEASURES

CLM94 was tested: 1) in two human cell lines (HMVEC-d, dermal microvascular endothelial cells; and 8305C, undifferentiated thyroid cancer) at 0.001-100 μm; 2) in ATC cells at the concentrations of 10, 30, and 50 μm; and 3) in an ATC cell line (AF) in CD nu/nu mice.

RESULTS

CLM94 significantly inhibited VEGF receptor-2 and epidermal growth factor receptor phosphorylation in HMVEC-d and proliferation in HMVEC-d and 8305C cells. A significant reduction of proliferation with CLM94 in ATC cells (P < 0.01, ANOVA) and a slight but significant reduction of proliferation with CLM94 30 and 50 μm in normal thyroid follicular cells (P < 0.01, ANOVA) were shown. CLM94 increased the percentage of apoptotic ATC cells dose-dependently (P < 0.001, ANOVA) and inhibited migration (P < 0.01) and invasion (P < 0.001). AF cell line was injected sc in CD nu/nu mice, and tumor masses became detectable 25 d afterward. CLM94 (40 mg/kg · d) significantly inhibited tumor growth (starting 10 d after the beginning of treatment). CLM94 significantly decreased the VEGF-A gene expression in the AF cell line and the VEGF-A protein and microvessel density in AF tumor tissues.

CONCLUSIONS

The antitumor and antiangiogenic activity of a new "cyclic amide" compound, CLM94, is very promising in ATC, opening the way to a future clinical evaluation.

An EPR study of Cu2+ doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) single crystals

The electron paramagnetic resonance spectra of Cu(2+) doped diaquabis(nicotinamide)bis(o-sulfobenzimidato-N)-cadmium(II) (hereafter, CdNAS) single crystals which were taken at room temperature are discussed. It was found from the analysis of the EPR data that the Cu(2+) ions substitute for magnetically inequivalent Cd(2+) ions. Two magnetically inequivalent Cu(2+)sites were observed. The principal values of the g and the hyperfine tensors were determined. The ground state wave functions of the unpaired electron of Cu(2+) ions in two sites were constructed and type of the distortion was determined.

EPR study of Cu(2+)-doped tetraaqua-di(nicotinamide)Co(II) saccharinate single crystals

The electron paramagnetic resonance spectra of Cu(2+) impurities in [Co(nicotinamide)(2)(H(2)O)(4)](saccharinate)(2) single crystals have been studied at ambient temperature in three mutually perpendicular planes. The angular variation of the spectra shows that the Cu(2+) ion substitutes the Co(2+) site in the lattice. The EPR spectra of Cu(2+) ions are characteristic of tetragonally elongated octahedral site. The spin-Hamiltonien parameters were obtained from the single crystal EPR analysis. The ground-state wave function of Cu(2+) ion in the lattice has been constructed.

EPR spectra of Cu(2+) doped [Zn(sac)2(dmen)] and [Zn(sac)2(paen)] single crystals

Cu(2+) doped single crystals of [Zn(sac)2(dmen)] (sac: saccharinate, dmen: N,N'-dimethylethylendiamine) and [Zn(sac)2(paen)], (paen: N,N'-bis(3-propylamine)ethylendiamine) complexes have been investigated by electron paramagnetic resonance (EPR) technique. Detailed investigations of the EPR spectra indicate that Cu(2+) ion substitute with Zn(2+) ion and forms tetrahedral complex in [Zn(sac)2(dmen)] and octahedral complex in [Zn(sac)2(paen)] hosts. Principal values of the g and hyperfine tensors are determined and the ground state wave functions of Cu(2+) ions are obtained using EPR parameters.

Indomethacin-saccharin cocrystal: design, synthesis and preliminary pharmaceutical characterization

PURPOSE

To design and prepare cocrystals of indomethacin using crystal engineering approaches, with the ultimate objective of improving the physical properties of indomethacin, especially solubility and dissolution rate.

MATERIALS AND METHODS

Various cocrystal formers, including saccharin, were used in endeavours to obtain indomethacin cocrystals by slow evaporation from a series of solvents. The melting point of crystalline phases was determined. The potential cocrystalline phase was characterized by DSC, IR, Raman and PXRD techniques. The indomethacin-saccharin cocrystal (hereafter IND-SAC cocrystal) structure was determined from single crystal X-ray diffraction data. Pharmaceutically relevant properties such as the dissolution rate and dynamic vapour sorption (DVS) of the IND-SAC cocrystal were evaluated. Solid state and liquid-assisted (solvent-drop) cogrinding methods were also applied to indomethacin and saccharin.

RESULTS

The IND-SAC cocrystals were obtained from ethyl acetate. Physical characterization showed that the IND-SAC cocrystal is unique vis-à-vis thermal, spectroscopic and X-ray diffraction properties. The cocrystals were obtained in a 1:1 ratio with a carboxylic acid and imide dimer synthons. The dissolution rate of IND-SAC cocrystal system was considerably faster than that of the stable indomethacin gamma-form. DVS studies indicated that the cocrystals gained less than 0.05% in weight at 98%RH. IND-SAC cocrystal was also obtained by solid state and liquid-assisted cogrinding methods.

CONCLUSIONS

The IND-SAC cocrystal was formed with a unique and interesting carboxylic acid and imide dimer synthons interconnected by weak N-Hcdots, three dots, centeredO hydrogen bonds. The cocrystals were non-hygroscopic and were associated with a significantly faster dissolution rate than indomethacin (gamma-form).

Allodynia and hyperalgesia suppression by a novel analgesic in experimental neuropathic pain

SCP-1, n-[alpha-(benzisothiazol-3(2ho-ona,1-dioxide-2yl)-acetyl]-p-aminophenol (100 nmol), when intrathecally injected, suppressed tactile allodynia and thermal hyperalgesia in a rat neuropathic pain model. The tactile allodynia suppression lasted for at least 4h and SCP-M1 (100 nmol), the main metabolite of SCP-1, displayed similar suppression as SCP-1, but shorter latency, indicating SCP-M1 may be the bioactive component of SCP-1. Acetaminophen was less potent than SCP-1 and SCP-M1. To study mechanisms underlying SCP-1 action, we recorded voltage-gated Ca(2+) channel currents in acutely isolated dorsal root ganglion neurons using the whole-cell patch-clamp technique. SCP-1 and SCP-M1 inhibited non-L-type calcium channel currents up to 23.0+/-2.3% and 23.1+/-3.5%, respectively, at a depolarized pulse to -10 mV from a holding potential of -80 mV. Acetaminophen only induced 6.8+/-1.0% inhibition. The results suggest SCP-1 possesses anti-nociceptive activity in the rat model involving calcium channel blocking properties.

Electron paramagnetic resonance studies of Cu2+ ion in tetraaqua-di(nicotinamide)Ni(II)-saccharinates single crystals

X-band (approximately 9.8 GHz) electron paramagnetic resonance (EPR) measurement at ambient temperature in three mutually perpendicular planes have been carried out on a single crystal of Cu2+ doped mixed ligand complex of Ni(II) with saccharin and nicotinamide [Ni(Nic)2(H2O)4](sac)2. The angular dependent spectra showed that the Cu2+ ion enters Ni2+ sites in the lattice and distorted local environment of Ni2+ site. The principal g and A values, covalency parameter (alpha'2), mixing coefficients (alpha and beta) and Fermi contact term (K) have been evaluated from the EPR analysis. The ground-state wave function of the Cu2+ ion has been constructed using the alpha'2, alpha and beta values. The nature of the distortion present in the lattice is obtained from the values of the mixing coefficients.

Synthesis and in vitro evaluation of pseudosaccharinamine derivatives as potential elastase inhibitors

Pseudosaccharinamine derivatives were evaluated for elastase inhibitory activity. Ester derivatives of pseudosaccharinamine displayed reversible and high inhibition of human leukocyte elastase (HLE) as compared to porcine pancreatic elastase (PPE). Cyanomethyl (2S,3S)-2-(1,1-dioxobenzo[d]isothiazol-3-ylamino)-3-methylpentanoate was found to inhibit HLE at Ki=0.8 microM.

Synthesis by Microwave Irradiation and Antidiarrhoeal Activity of Benzotriazinone and Saccharine Derivatives

The synthesis by microwave irradiation and the biological results of novel benzotriazinone and saccharine derivatives with potential antidiarrhoeal activity is described. Conventional and microwave heatings were compared for the reactions. Good yields and short reaction times are the main advantages of our synthetic route. Among the tested compounds, compound 12 inhibited motility both in in-vitro and in-vivo tests.

Absence of mouse REC8 cohesin promotes synapsis of sister chromatids in meiosis

REC8 is a key component of the meiotic cohesin complex. During meiosis, cohesin is required for the establishment and maintenance of sister-chromatid cohesion, for the formation of the synaptonemal complex, and for recombination between homologous chromosomes. We show that REC8 has an essential role in mammalian meiosis, in that Rec8 null mice of both sexes have germ cell failure and are sterile. In the absence of REC8, early chromosome pairing events appear normal, but synapsis occurs in a novel fashion: between sister chromatids. This implies that a major role for REC8 in mammalian meiosis is to limit synapsis to between homologous chromosomes. In all other eukaryotic species studied to date, REC8 phenotypes have been restricted to meiosis. Unexpectedly, Rec8 null mice are born in sub-Mendelian frequencies and fail to thrive. These findings illuminate hitherto unknown REC8 functions in chromosome dynamics during mammalian meiosis and possibly in somatic development.

N-cinnamoylsaccharin

The title compound [systematic name: 2-cinnamoyl-1,2-benzisothiazol-3(2H)-one 1,1-dioxide], C16H11NO4S, contains both saccharin and cinnamoyl groups. The molecule is approximately planar in the solid state, and adjacent molecules are connected by C-H...O and C-H...pi(phenyl) interactions. In the C-H...pi interaction, the C...CgA distance is 3.916 (4) A (CgA is the non-fused benzene ring centroid) and the C-H...pi angle is 156 (2) degrees . A feature of the molecular geometry is the narrow C-S-N angle of 92.51 (9) degrees in the five-membered ring. This angle relieves strain from the ring and makes it possible for the whole saccharin group to become quite planar.

Identification of Ligands for Two Human Bitter T2R Receptors

Earlier, a family of G protein-coupled receptors, termed T2Rs, was identified in the rodent and human genomes through data mining. It was suggested that these receptors mediate bitter taste perception. Analysis of the human genome revealed that the hT2R family is composed of 25 members. However, bitter ligands have been identified for only three human receptors so far. Here we report identification of two novel ligand-receptor pairs. hT2R61 is activated by 6-nitrosaccharin, a bitter derivative of saccharin. hT2R44 is activated by denatonium and 6-nitrosaccharin. Activation profiles for these receptors correlate with psychophysical data determined for the bitter compounds in human studies. Functional analysis of hT2R chimeras allowed us to identify residues in extracellular loops critical for receptor activation by ligands. The discovery of two novel bitter ligand-receptor pairs provides additional support for the hypothesis that hT2Rs mediate a bitter taste response in humans.

Diaquabis(pyridine-2-carboxamide-κ2N1,O2)nickel(II) disaccharinate tetrahydrate

In the crystal structure of the title compound, [Ni(C6H6N2O)2(H2O)2](C7H4NO3S)2.4H2O or [Ni(pia)2(H2O)2](sac)2.4H2O (pia is picolinamide or pyridine-2-carboxamide, and sac is the saccharinate anion), the Ni2+ cation, located on a centre of symmetry, is coordinated by two symmetry-related aqua ligands together with a pair of symmetry-related bidentate pia molecules and exhibits a distorted octahedral environment. The unique unligated sac anion in the asymmetric unit resides on a general position and has a single negative charge. The coordinated water molecules link the sac ions to the metal complex via O-H...O hydrogen bonds. In addition, the sac ions are linked to the metal complex via intermolecular pi-pi interactions between the benzene ring of the sac ion and the pyridine ring of a pia ligand. Each uncoordinated water molecule is hydrogen bonded to sac moieties through O-H...O and O-H...N hydrogen bonds.

Expression of cancer testis antigens in pancreatic carcinoma cell lines, pancreatic adenocarcinoma and chronic pancreatitis

In order to define antigens that might be suitable as vaccines for pancreatic carcinoma, we investigated the composite expression of 10 cancer testis (CT) antigens (SCP-1, NY-ESO-1, SSX-1, SSX-2, SSX-4, GAGE, MAGE-3, MAGE-4, CT-7 and CT-8) by Reverse Transcriptase-PCR (RT-PCR) in fresh biopsies of human pancreatic adenocarcinoma, chronic pancreatitis and pancreatic carcinoma cell lines. While all CT genes were frequently expressed in cell lines derived from pancreatic cancer, no expression of MAGE-3, SSX-1, SSX-2, NY-ESO-1 and CT-7 was detected in fresh tumor biopsies, and MAGE-4 (1/52), SSX-4 (1/39) and CT-8 (2/41) were only rarely expressed. In contrast, HOM-TES-14/SCP-1 was expressed in 48% (29/61) and GAGE in 21% (13/61) of cases, respectively. One CT gene was expressed by 59% (75% in male, 46% in female patients; p = 0.05) and 2 or more CT genes by 15% of the samples. SCP-1 protein expression correlated well with mRNA expression. While SCP-1 and GAGE were absent in normal pancreas, they were found in 2/8 (SCP-1) and 1/8 (GAGE) samples of chronic pancreatitis, respectively, supporting the concept of chronic pancreatitis as a premalignant condition. SCP-1 and GAGE represent promising candidates for vaccine development in pancreatic carcinoma. Whether SCP-1 and GAGE expression identify cases of chronic pancreatitis with a high risk of malignant transformation remains to be shown.

Soil persistence and metabolism of iodosulfuron in winter wheat crops

The sulfonylurea herbicide iodosulfuron 1 has been applied post-emergence at the dose of 10 g a.i. ha-1 on winter wheat crops grown on sandy-loam (Melle) or on clay soils (Leke, Gistel and Zevekote). The dissipation of iodosulfuron in soil followed a first order kinetics. After the application of iodosulfuron at Melle at the beginning of April 2000, the soil half-life of iodosulfuron in the 0-10 cm surface soil layer was 60 days. At the end of September 2000, i.e. one month after the winter wheat harvest, only 8% of the applied dose of iodosulfuron remained in soil as iodosulfuron itself. At the mid of November, iodosulfuron 1 was no more detected in the 0-10 cm surface soil layer. From the beginning of May till the end of July 2000, low concentrations of iodosulfonamide 2 and of iodosaccharin 3 were observed in the 0-10 cm surface soil layer, their maximum concentrations being 0.7 and 1.5 micrograms of equivalents of iodosulfuron 1 kg-1 dry soil, respectively. At the end of September, the metabolites 2 and 3 were no more detected in soil. At Leke, Gistel and Zevekote, iodosulfuron was applied at the beginning of May 2001, and its half-life in the 0-10 cm surface soil layer was 44, 30 and 35 days, respectively. The later application of iodosulfuron and the higher soil pH (about 8) at Leke, Gistel and Zevekote should explain the soil half-lives lower than at Melle (soil pH 6.2). In all the trials and since the treatment till the mid of November, iodosulfuron 1 and its metabolites 2 and 3 were not detected in the 10-15 and 15-20 cm surface soil layers.

A convenient synthesis by microwave heating and pharmacological evaluation of novel benzoyltriazole and saccharine derivatives as 5-HT(1A) receptor ligands

A series of novel 1,2,3-4-benzoyltriazole and saccharine derivatives were designed and synthesized by microwave heating. They were evaluated on a battery of receptors, including serotonin 5-HT(1A,) 5-HT(2A) and 5-HT(2C), and the most interesting compounds were further evaluated on dopaminergic D(1), D(2) and adrenergic alpha(1), alpha(2) receptors. Conventional and microwave heating of the reactions were compared. Synthesis by microwave heating gave the desired compounds in better yields than those obtained by conventional heating. The overall times for the syntheses were considerably reduced. All compounds displayed moderate affinity for 5-HT(1A) receptor. The most interesting compound 33 showed a high affinity (K(i)=93 nM) which was combined with no affinity on the other receptors considered.

Synthesis and properties of N-substituted saccharin derivatives

Four different routes for the synthesis of saccharin containing peptides were studied. While reactions between saccharin sodium and alpha-halogeno acids were limited to two examples, reactions of sulfobenzoic anhydride (4) or saccharin-N-carboxylate (6) with amino acid esters yielded the ring opened products 5 and 7. Finally, we found, that the reaction between the benzoxathiol derivative 8 and amino acid derivatives represents a versatile route to the peptidic compounds 9 and 11. Hydrolysis and hydrogenolysis were studied, and by combination of the different routes the "saccharin tripeptides" 18 were obtained. Structures and stereochemistry were elucidated by spectroscopic and chromatographic methods. Selected compounds were tested as sweeteners or as inhibitors of elastase, but no exiting results were found.

On the short carbonyl bond in bis[mu-1,2-benzisothiazol-3(2H)-one 1,1-dioxido-kappa2N:O]bis[[1,2-benzisothiazol-3(2H)-one 1,1-dioxido-kappaN]bis(imidazole)copper(II)]

The short carbonyl bond in the title compound, [Cu(2)(C(7)H(4)NO(3)S)(4)(C(3)H(4)N(2))(4)] [Liu, Huang, Li & Lin (1991). Acta Cryst. C47, 41-43], is an artifact of disorder in the isothiazol-3(2H)-one 1,1-dioxide part of the 1,2-benzisothiazol-3(2H)-one entity. In the present redetermination, all bond dimensions in the centrosymmetric dinuclear molecule are normal. The five-coordinate Cu atom shows trigonal-bipyramidal coordination. Hydrogen bonds from the imidazole donor ligand link adjacent molecules into a two-dimensional layer structure.

trans-Bis(ethanolamine-N,O)bis(saccharinato-N)copper(II)

In the title complex, [Cu(C(7)H(4)NO(3)S)(2)(C(2)H(7)NO)(2)], the Cu(II) centre lies on an inversion centre and exhibits octahedral coordination, with the two ethanolamine (Hea) and two saccharinate [sac; anionic 1,2-benzisothiazol-3(2H)-one 1,1-dioxide] ligands in a trans configuration. The bidentate Hea ligands bridge axial and equatorial positions and the sac anions occupy equatorial sites around the distorted octahedral copper(II) centre [Cu--O = 2.3263 (16), Cu--N(Hea) = 1.9923 (16) and Cu--N(sac) = 2.1776 (16) A].

Hepatic kinetics of SCP-1 (N-[alpha-(1,2-benzisothiazol-3(2H)-ona-1, 1-dioxide-2-yl)-acetyl]-p-aminophenol) compared with acetaminophen in isolated rat liver

The hepatic disposition of a new analgesic, SCP-1, a derivative of acetaminophen, was studied in the isolated perfused rat liver using a recirculating system. The aim of this study was to compare the kinetic parameters of this molecule with those of acetaminophen. Sprague-Dawley rat (230-330 g) livers were perfused for 2 h with 250 ml Krebs-Henseleit bicarbonate buffer containing SCP-1 or acetaminophen, 0.07 mmol l(-1) (n=4), 0.28 mmol l(-1) (n=4), and 0.8 mmol l(-1) (n=4) (approximately one, four and ten times the therapeutic doses in man, respectively). Perfusate samples were collected from the efflux at various times. The SCP-1 and acetaminophen perfusate concentrations were assayed by a HPLC method. Pharmacokinetic analysis was carried out using a computer program. There were significant differences between the hepatic kinetics of SCP-1 and those of acetaminophen. Thus, SCP-1 elimination half-life (mean 14.8+/-10.0 min) was shorter than that of the acetaminophen (186.1+/-27.7 min) (t=11.6, P=0.0001). While the half-life of SCP-1 increases with concentration, the half-life of acetaminophen remains constant as the concentration increases. The hepatic clearance was higher for SCP-1 than acetaminophen (mean 19.01+/-14.5 ml min(-1) vs. 1.29+/-0.08 ml min(-1), respectively) (t=2.44, P<0.05), and it behaved according to dose-dependent kinetics. The SCP-1 extraction ratio was higher (mean 0.63+/-0.49) than for acetaminophen (0.04+/-0.01) (t=2.41, P<0.05) and this parameter tended to decrease as the perfusate concentrations of SCP-1 increased. It was concluded that the hepatic kinetics of SCP-1 behaved according to dose-dependent kinetics, and statistically significant differences were found between pharmacokinetics parameters of both drugs studied.

Design and synthesis of N-alkylated saccharins as selective alpha-1a adrenergic receptor antagonists

Benign prostatic hyperplasia can be managed pharmacologically with alpha-1 adrenergic receptor antagonists. Agents that demonstrate selectivity for the alpha-1a receptor subtype may offer advantages in clinical applications with respect to hypotensive side effects. The N-alkylated saccharins reported here represent a new class of subtype selective alpha-1a adrenergic receptor antagonists which demonstrate potent effects on prostate function in vivo and are devoid of blood pressure side effects.

Phthalimidomethyl as a drug pro-moiety. Probing its reactivity

Phthalimidomethyl derivatives 1, encompassing a wide range of leaving group abilities, are rapidly hydrolysed to the corresponding phthalamic acid via rate-determining attack at the phthalimide carbonyl group.

Amino acid-derived phthalimide and saccharin derivatives as inhibitors of human leukocyte elastase, cathepsin G, and proteinase 3

Amino acid-derived phthalimide and saccharin derivatives have been investigated for their inhibitory activity toward the serine proteinases human leukocyte elastase, cathepsin G, and proteinase 3. The saccharin derivatives were found to be effective time-dependent inhibitors of elastase and proteinase 3 (kobs/[I] values ranged between 180 and 3620 M-1 S-1) and showed weak or no inhibition toward cathepsin G. The corresponding phthalimide derivatives were found to be inactive.

A novel class of cyclic beta-dicarbonyl leaving groups and their use in the design of benzisothiazolone human leukocyte elastase inhibitors

Human leukocyte elastase (HLE) has been proposed to be a primary mediator of pulmonary emphysema, and inhibitors of this enzyme should be effective in the treatment of emphysema and other pulmonary diseases. We have discovered a novel class of alicyclic and heterocyclic leaving groups which share one common structural feature, a cyclic beta-dicarbonyl. This design concept for leaving groups has not been previously reported. A structure-activity relationship has been developed and the concept extended to several types of alicyclic and heterocyclic beta-dicarbonyl systems. This work led to the identification of a potent (K*i of 0.066 nM) and tissue stable (in vitro: blood t1/2 = 160 min, liver t1/2 > 240 min) benzisothiazolone HLE inhibitor, WIN 65936 (13b).

Prodrugs of nitroxyl as potential aldehyde dehydrogenase inhibitors vis-a-vis vascular smooth muscle relaxants

The synthesis and the chemical/biological properties of N-hydroxysaccharin (1) (2-hydroxy-1,2-benzisothiazol-3(2H)-one 1,1-dioxide), a nitroxyl prodrug, are described. When treated with 0.1 M aqueous NaOH, 1 liberated nitroxyl (HN=O), a known inhibitor of aldehyde dehydrogenase (AlDH), in a time-dependent manner. Nitroxyl was measured gas chromatographically as its dimerization/dehydration product N2O. Under these conditions, Piloty's acid (benzenesulfohydroxamic acid) also gave rise to HNO. However, whereas Piloty's acid liberated finite quantities of nitroxyl when incubated in physiological phosphate buffer, pH 7.4, formation of nitroxyl from 1 was minimal. This was reflected in the differential inhibition of yeast AlDH (IC50 = 48 and > 1000 microM) and the differential relaxation of preconstricted rabbit aortic rings in vitro (EC50 = 1.03 and 14.0 microM) by Piloty's acid and 1, respectively. The O-acetyl derivative of 1, viz., N-acetoxysaccharin (13a), was much less active in both assays. It is concluded that N-hydroxysaccharin (1) is relatively stable at physiological pH and liberates nitroxyl appreciably only at elevated pH's. As a consequence, neither 1 nor its O-methyl (8a) and O-benzyl (8b) derivatives were effective AlDH inhibitors in vivo when administered to rats at 1.0 mmol/kg.

Carbethoxylating agents as inhibitors of aldehyde dehydrogenase

N,O-Dicarbethoxy-4-chlorobenzenesulfohydroxamate (1c) and O-carbethoxy-N-hydroxysaccharin (6), both potential carbethoxylating agents, inhibited yeast aldehyde dehydrogenase (AlDH) with IC50's of 24 and 56 microM, respectively. The esterase activity of the enzyme was commensurably inhibited. AlDH activity was only partially restored on incubation with mercaptoethanol (20 mM) for 1 h. On incubation with rat plasma, 1c liberated nitroxyl, a potent inhibitor of AlDH. Under the same conditions, nitroxyl generation from 6 was minimal, a result compatible with a previous observation that nitroxyl generation from N-hydroxysaccharin (7), the product of the hydrolysis of the carbethoxy group of 6, was minimal at physiological pH. Since chemical carbethoxylating agents represented by the O-carbethoxylated N-hydroxyphthalimide, 1-hydroxybenzotriazole, and N-hydroxysuccinimide (8, 9, and 10, respectively) likewise inhibited yeast AlDH, albeit with IC50's 1 order of magnitude higher, we postulate that 1c and 6 act as irreversible inhibitors of AlDH by carbethoxylating the active site of the enzyme.

The Gabriel-Colman rearrangement in biological systems: design, synthesis and biological evaluation of phthalimide and saccharin derivatives as potential mechanism-based inhibitors of human leukocyte elastase, cathepsin G and proteinase 3

The results of a structure-activity relationship study focusing on the interaction of a series of phthalimide and saccharin derivatives with leukocyte elastase, cathepsin G and proteinase 3 are described. The phthalimide derivatives were found to be inactive while some of the saccharin derivatives were found to be fair inhibitors of these enzymes.

A prodrug approach to increasing the oral potency of a phenolic drug. Part 2. Pharmacodynamics and preliminary bioavailability of an orally administered O-(imidomethyl) derivative of 17 beta-estradiol

The O-saccharinylmethyl prodrug of 17 beta-estradiol was about nine times as potent, based on 50% effective dose (ED50) values, as 17 beta-estradiol when each was given as an oral dose to ovariectomized rats. Similarly, a significant lowering of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels at 24 h was observed when an ED50 dose of the prodrug was given but not when an equimolar dose of 17 beta-estradiol was given orally. However, when given intravenously, there was no difference in potency between the two drugs. In the bioavailability studies, a significantly longer half-life (approximately 5-7 times) for 17B-estradiol was observed when the prodrug was given orally than when 17 beta-estradiol was given orally or when the prodrug or 17 beta-estradiol were given intravenously. This result was consistent with an observed five-fold enhancement in the oral bioavailability of 17 beta-estradiol when the prodrug was given.

A prodrug approach to increasing the oral potency of a phenolic drug. 1. Synthesis, characterization, and stability of an O-(imidomethyl) derivative of 17 beta-estradiol

An O-(saccharinylmethyl) prodrug was synthesized to improve the poor oral potency of the phenolic drug 17 beta-estradiol. This O-(imidomethyl) type of prodrug was designed to undergo chemical hydrolysis and to be a poor substrate for enzymatic hydrolysis. At 37 degrees C, it was found to exhibit half-lives of about 13 min in 50% methanol:pH 7.0 (v/v) phosphate buffer, about 3 min in rat plasma, about 15 min in human plasma, and about 50 min in 20% rat liver homogenate. Introduction of the enzyme poison tetraethyl pyrophosphate or the protein denaturant sodium fluoride into rat plasma had no significant effect on the half-life. Thus, the observed increased rate of hydrolysis in biological media is not due to enzymatic catalysis but to a nonspecific solventlike effect. The fact that the rate of hydrolysis in the methanol:buffer exhibited a first-order dependence on the hydroxide ion concentration and that the rate of hydrolysis increased with increasing methanol concentrations up to 70% supported an SN2 mechanism of hydrolysis for the prodrug. These results suggest that an O-(imidomethyl) type prodrug is insensitive to enzymatic catalysis of hydrolysis yet may hydrolyze quickly enough to release 17 beta-estradiol faster than 17 beta-estradiol is conjugated and excreted.

Efficient inhibition of human leukocyte elastase and cathepsin G by saccharin derivatives

A series of saccharin derivatives I has been synthesized and evaluated for their inhibitory activity toward human leukocyte elastase and cathepsin G. Most of the compounds were found to be efficient and time-dependent inhibitors of elastase. Inactivated elastase was found to regain its activity almost fully after 24 h (80-90% activity) and the half-lives of reactivation ranged between 12-15 h. Addition of hydroxylamine to fully-inactivated enzyme led to rapid and complete recovery of enzymatic activity. A tentative mechanism of action is proposed on the basis of biochemical and model studies.

Inhibition of human leucocyte elastase by fatty acyl-benzisothiazolinone, 1,1-dioxide conjugates (fatty acyl-saccharins)

Derivatives of benzisothiazolinone 1,1-dioxide (saccharin) N-acetylated with aliphatic and aromatic substituted aliphatic acyl groups were prepared. The inhibitory activity of the compounds was assayed against human leucocyte elastase (EC 3.4.21.37) and several other proteases. The IC50 values for inhibition of the human leucocyte elastase decreased with increasing length of the acyl residue, and reached a minimum value at C16 (2 microM). This phenomenon and the decrease of the inhibition by surfactants or by saturation of the enzyme with palmitic acid, indicates that in addition to acylation, hydrophobic interactions are also involved in the inhibition of this proteinase by compounds substituted with acyl groups containing at least 12 carbon atoms. The inhibitory activity of N-palmitoyl-benzisothiazolinone 1,1-dioxide (palmitoyl-saccharin) is about 14 times higher toward human leucocyte elastase than for thrombin (EC 3.4.21.5), and several hundred times, compared to porcine pancreatic elastase (EC 3.4.21.36) and to plasmin (EC 3.4.21.7). Fatty acylated saccharin derivatives were seen to bind in a saturable fashion to insoluble elastin, and decreased the susceptibility of this protein to hydrolysis by human leucocyte elastase.

Update on artificial sweeteners and bladder cancer

Review of the most recent epidemiologic studies indicates there is no detectable association between artificial sweetener consumption and bladder cancer. The summary relative risk from a meta-analysis of all case-control studies approaches unity (RR .97). This analysis, in combination with new evidence for a unique mechanism of saccharin carcinogenicity in the male rat, leads to the conclusion that saccharin is not related to bladder cancer in humans.

The effects of phthalimide and saccharin derivatives on low-density lipoprotein (LDL) and high-density lipoprotein (HDL) receptor activity and related enzyme activities

The hypolipidemic agents, phthalimide, saccharin, o-(N-phthalimido) acetophenone, N-(p-chlorobenzoyl) sulfamate, and o-chlorobenzylsulfonamide affected low-density lipoprotein (LDL) and high-density lipoprotein (HDL) receptor activity and lipoprotein degradation. In isolated rat hepatocytes, rat aorta foam cells, and human fibroblasts, LDL receptor activity, which is dependent on apo-B and -E, was inhibited by the drugs in a dose-dependent manner. LDL degradation was accelerated in the hepatocytes, while it was inhibited in aorta cells and fibroblasts. The drugs enhanced HDL receptor activity, dependent on apo-E and -A1, and HDL degradation in the hepatocytes, whereas in fibroblasts and aorta cells HDL receptor binding and degradation were suppressed. In parallel, activities of acyl CoA acyl transferase, sn-glycerol-3-phosphate acyl transferase, and heparin-induced lipoprotein lipase decreased and activities of HMG-CoA reductase and cholesterol oleate-ester hydrolase increased. In fibroblasts the presence of drugs enhanced HDL binding of intracellular cholesterol. In vivo studies demonstrated that phthalimide and saccharin treatment enhanced the clearance of HDL and decreased the clearance of LDL from the serum of rats. The results suggest that the mode of action of the agents is to modulate the lipoprotein receptor and, thereby, the clearance of lipids from peripheral tissue as part of the hypolipidemic activity.

Effect of the novel synthetic protease inhibitor furoyl saccharin on elastase-induced emphysema in rabbits and hamsters

Furoyl saccharin, a novel heterocyclic acylating agent which has been previously found to possess a potent inhibitory capacity in vitro for elastase and other serine proteases, has been investigated in vivo in two acute animal models of emphysema. In hamsters, intratracheal (i.tr.) administration of 0.1 mg porcine pancreatic elastase resulted seven days later, in a 42% increase of the mean linear intercept (Lm). Addition of 0.3 mg to 0.3 mg furoyl saccharin to elastase exhibited a partial, not dose-related, but statistically significant inhibition of the increase of LM. Addition of 1 mg furoyl saccharin (equivalent to a dose of 12.5 mg/kg) completely abolished the increase in Lm. In the rabbit i.tr. instillation of 3.7 mg porcine pancreatic elastase induced within seven days, a 48% increase of the Lm, a 27% decrease of the internal surface area (ISA) of the lungs and a 33% decrease of the ISA corrected to an arbitrary total lung volume of 70 ml (ISA70). Furoyl saccharin given i.tr. 15 min prior to elastase at the doses 3, 10 and 20 mg prevented significantly in a dose-related manner, the changes in Lm, ISA and ISA70. The highest furoyl saccharin dose (equivalent to a dose of 10.8 mg/kg) completely protected against the emphysematous lesion. Additionally furoyl saccharin (20 mg i.tr.) prevented in the rabbit model the depletion in lung insoluble elastin and the increase in salt soluble collagen induced by the elastase administration. These results show that furoyl saccharin also in vivo has a marked antielastase activity.

Characterization of aminosaccharins in commercial sodium saccharin produced by the Maumee process

The most abundant polar impurities detected by ion-pair high-pressure liquid chromatography of sodium saccharin produced by the Maumee process were identified as 5- and 6-aminosaccharin. The combined levels of these compounds in the samples analysed ranged from 99 to 152 mg/kg. Other less abundant polar impurities identified in Maumee process sodium saccharin were 7-aminosaccharin and o-sulphamoylbenzoic acid. Mutagenicity assays of 5-aminosaccharin, 6-aminosaccharin and a polar impurity fraction isolated from Maumee saccharin, gave negative results.

The effect of furoyl saccharin, a novel non-peptidic acylating protease inhibitor, on experimental emphysema in the hamster

Furoyl saccharin was evaluated for its ability to prevent the development of emphysematous lesions produced in hamsters by the exposure to aerosolized papain (3% for 3 h). Pretreatment with intratracheal furoyl saccharin (at the doses of 0.3, 1, 3 mg) reduced the appearance of papain-induced emphysema as evaluated by both physiologic (static compliance) and histologic (mean linear intercept and internal surface area of the lungs) methods. Inhibition was dose-related with maximal reduction of changes in static compliance (74%), mean linear intercept (84%) and internal surface area (65%) observed after a dose of 3 mg. This is the first time that a non-peptide acylating inhibitor of serine proteases is reported to be affective in preventing the development of experimental emphysema.

Antihyperlipidemic activity of saccharin analogues in rodents

Saccharin analogues were observed to be potent antihyperlipidemic agents at 20 mg/kg/day in rodents, significantly reducing both serum cholesterol and triglyceride levels in both normal and atherogenic mice. The saccharin analogues suppressed in vitro and in vivo liver enzymatic activity of acetyl-CoA synthetase, citrate lyase, and mitochondrial citrate exchange leading to a reduction of available cytoplasmic acetyl-CoA, which is required for the synthesis of cholesterol and fatty acids. Liver acetyl-CoA carboxylase, phosphatidate phosphohydralase, and glycerol-3-phosphate acyl transferase activities were markedly reduced by the saccharin analogues. Suppression of these enzymes would lead to a reduction of triglyceride synthesis. The saccharin analogues accelerated bile excretion of cholesterol metabolites and increased the fecal excretion of the cholesterol, triglycerides, neutral lipids, and phospholipids. The liver and plasma lipoprotein lipid content (including cholesterol, triglycerides, and neutral lipids) was markedly reduced by the saccharin analogues, whereas phospholipid content was elevated. The reduction of lipid content of serum chylomicron, very low-density, low-density, and high-density lipoprotein fractions by the saccharin analogues indicates that these agents may be useful in controlling hyperlipidemic diseases where specific lipoprotein fractions are elevated.

Non-mutagenicity of 3-dimethylamino-psi-saccharin to Salmonella typhimurium

3-Dimethylamino-psi-saccharin has been confirmed as non-mutagenic to Salmonella typhimurium when evaluated in vitro in the presence of induced rat liver S9 mix.

Hypolipidemic activity of phthalimide derivatives. 3. A comparison of phthalimide and 1,2-benzisothiazolin-3-one 1,1-dioxide derivatives to phthalimidine and 1,2-benzisothiazoline 1,1-dioxide congeners

Previously it has been observed that N-substituted phthalimide derivatives with chain lengths of four carbon or oxygen atoms showed potent hypolipidemic activity in rodents at 20 (mg/kg)/day ip. The 1,2-benzisothiazolin-3-one 1,1-dioxide (saccharin) nucleus, itself, had also been observed to be active at the same dose. An investigation was undertaken to examine a series of 1,2-benzisothiazolin-3-one 1,1-dioxide analogues for their hypolipidemic activity in mice and to compare them to their respective phthalimide congeners. In addition, a series of 1,2-benzisothiazoline 1,1-dioxide and phthalimidine analogues was prepared, and their hypolipidemic activity was compared to the phthalimide analogues. These studies show that the respective congeners of 1,2-benzisothiazolin-3-one 1,1-dioxide compared favorably to phthalimide congeners in reducing serum triglyceride and cholesterol levels in male CF1 mice at 20 (mg/kg)/day ip. Of the saccharin derivatives, 3-oxo-1,2-benzisothiazoline-2-propionic acid 1,1-dioxide was the most effective in lowering serum cholesterol levels by 53% after 16 days dosing and 3-oxo-1,2-benzisothiazoline-2-valeric acid 1,1-dioxide lowered serum triglycerides 56% after 14 days dosing. The 1,2-benzisothiazoline 1,1-dioxide and phthalimidine compounds were less active as hypolipidemic agents than their 1,2-benzisothiazolin-3-one 1,1-dioxide and phthalimide analogues, respectively.

Inhibition of elastase and other serine proteases by heterocyclic acylating agents

The N-acylsaccharins and N-acylbenzoisothiazolinones form a new class of acylating inhibitors of the serine proteases with a broad spectrum of activity. However, they are unique in that they are able to differentiate between various serine proteases because of the differential stability of the presumptive acyl-enzyme formed. Furoyl saccharin was the best studied among this class of inhibitors. We report evidence that the amide bond in the heterocyclic ring of this compound is cleaved by porcine pancreatic and human leukocyte elastases and chymotrypsin, forming acyl-enzymes. Radioisotope studies indicate that the saccharin portion of furoyl saccharin is attached to these enzymes in approximately a 1:1 molar ratio with enzyme, blocking the active site serine. The acylelastases thus prepared are unusually stable to hydrolysis, with kdeacyl values at neutral pH of 2.3 x 10(-6) s-1 for porcine pancreatic elastase and 1.4 x 10(-6) s-1 for human leukocyte elastase. Trypsin appears to be inhibited by a different mechanism. These data suggest a new approach to the design of specific synthetic protease inhibitors.

The fate of saccharin impurities: the metabolism and excretion of 3-amino [3-14C]benz[d]-isothiazole-1,1-dioxide and 5-chlorosaccharin in the rat

1. 3-Amino[3-14C]benz[d]isothiazole-1, 1-dioxide was prepared from [3-14C]-saccharin. IT was well adsorbed on oral administration to rats (25 mg/kg) with only 2% of the 14C in the faeces. The absorbed material was rapidly eliminated with about 87% dose in the urine in 24 h and 91% in 4 days. Little 14C (0.5% of dose) was present in the carcass 4 days after dosing. Most of the 14C in the 0--24 h urine (99%) was present as unchanged 3-aminobenz[d]isothiazole-1,1-dioxide, the rest being an unidentified metabolite. 2. 5-Chlorosaccharin was excreted unchanged after oral administration to rats (80 mg/kg) with 76% dose in the urine in 24 h and 81% in 4 days. Only 4% was detected in the faeces. There was no significance hydrolysis (less than 0.5%) to 5-chloro-2-sulphamoylbenzoic acid. 3. The extent of metabolism of these and other compounds related to saccharin showed good agreement with the extent of their partitioning into organic solvents.

The fate of saccharin impurities: the excretion and metabolism of [3-14C]Benz[d]-isothiazoline-1,1-dioxide (BIT) in man and rat

1. The 14C label of [3-14C]benz[d]isothiazoline-1,1-dioxide (BIT) (40 mg/kg) was rapidly eliminated (97% dose in 24 h), largely in the urine (92% dose in 24 h), after oral administration to rats. Larger doses (400 mg/kg) were eliminated more slowly after oral or parenteral administration (45--60% within 24 h) mostly in the urine (42--53%). Little 14C (2--3% dose) was present in the faeces after intraperitoneal (400 mg/kg) or low oral (40 mg/kg) doses, but the presence of larger amounts (12% dose) after larger oral doses (400 mg/kg) indicated incomplete absorption. 2. Metabolites identified in the urine of rats were saccharin (about 30% of urinary 14C), 2-sulphamoylbenzoic acid (about 35% urinary 14C) and 2-sulphamoylbenzyl alcohol (15% urinary 14C) in addition to unchanged compound (5--10% urinary 14C). The urine also contained a polar, labile metabolite that gave BIT on acid hydrolysis. The pattern of metabolism was not significantly affected by dose or route of administration. 3. In man, urine was the major route of elimination of 14C (93% dose) after administration of 14C-BIT (0.5 mg/kg). Negligible 14C was recovered in the faeces (less than 1% dose). Excretion was rapid (59% dose in 6 h; 80% dose in 12 h) and little 14C was eliminated on the second (3%) or subsequent days after dosing. 4. Identified metabolites in man included saccharin (about 50% of urinary 14C), 2-sulphamoylbenzoic acid (7% urinary 14C) and 2-sulphamoylbenzyl alcohol (8% urinary 14C unconjugated and 40% conjugated) with negligible unchanged compound. Only traces of the polar labile metabolite were detected. 5. the possible significance of metabolic interrelationships of toluene-2-sulphonamide and BIT to studies on the metabolism of saccharin are discussed.