Pharmacokinetic Properties and Interactions with Blood Components of N4-Hexadecyl-1-β-d-arabinofuranosylcytosine (NHAC) Incorporated into Liposomes

N⁴-Hexadecyl-1-β-d -arabinofuranosylcytosine (NHAC) is a new lipophilic derivative of 1-β-d -arabino-furanosylcytosine (ara-C) with strong antitumour activity. The interactions of NHAC incorporated into small unilamellar liposomes of different compositions with blood components were evaluated. In comparison with ara-C, NHAC is highly protected against deamination to inactive arabinofurano-syluracil (ara-U) in human plasma, resulting in only 2% conversion into ara-U after 4 h incubation at 37°C, whereas from ara-C more than 80% was deaminated. In in-vitro incubations with human blood, it was found that NHAC was transferred from the liposomes at about 47% efficiency to plasma proteins, particularly to albumin and to the high and low density lipoproteins. The remaining part of NHAC was bound to erythrocytes (50%) and to leucocytes (3%). The addition of poly(ethylene) glycol-modified phospholipids to the liposomes (PEG liposomes), which were composed of soy phosphatidylcholine and cholesterol (plain liposomes), did not significantly prevent the fast transfer of NHAC from the liposomes to the blood components. Pharmacokinetic studies in mice revealed that NHAC had biphasic kinetics in blood with a t 1/2α of 16 min and a 1/2β of 3·8 h when the drug was formulated in plain liposomes and a t 1/2α of 15 min and a t 1/2β of 9·67 h in PEG liposomes, respectively. NHAC was predominantly distributed in the liver with 29% of the injected dose found after 30 min. However, no accumulation occurred in the liver and NHAC was eliminated with biphasic kinetics resulting in a t 1/2α of 53 min and a t 1/2β of 11·8 h. In spleen, kidney and bone marrow the levels of NHAC remained low. In summary, NHAC is highly resistant against deamination and rapidly transferred from the liposomes to the blood components, independently of the liposome compositions tested.     

Einige N-funktionelle Derivate von N-(α-Tosylaminoacyl)-β-alaninen

Syntheses of dipeptidenitriles 1a-e starting from α-tosylaminoacidchlorides and β-aminopropionitrile and their conversion to the esters of dipeptide-imide acids 2a-d , esters of dipeptide acids 5a-d , to amides of dipeptide acids 6a-d and amidines of dipeptide acids 4a-e are described. Condensations of amidines of tosyldipeptide acids 3a, c with ethyl acetoacetate yield pyrimidines 7a, c .     

A three-step synthesis of (±)-β-methyleneaspartic acid

A simplified, three-step synthesis for (±)-β-methyleneaspartic acid is described. Condensation of diethyl malonate with ethyl pyruvate gives 1,1,2–tricarbethoxyprop-1-ene, which is α-aminated with chloramine to give 1-amino-1,1,2-tricarbethoxyprop-2-ene. The latter is hydrolyzed in acid to give the title compound.     

Effects of N-substituted analogs of (−)-α-acetylmethadol and (−)-α-methadol on schedule-controlled behavior

The behavior of the pigeon maintained under a variable-interval schedule of food presentation was used to compare the activity of four novel N-substituted acetylmethadol and methadol analogs with that of methadone and (-)-α-acetylmethadol (LAAM). All of the acetylmethadol and methadol analogs had narcotic agonist activity, as defined by the reversibility of their behavioral effects by naloxone. The effect of the N-substituted analogs on variable-interval responding was similar to that of methadone and LAAM, but all these compounds had a slower onset of action than methadone and a shorter duration of action than LAAM. None of the N-substituted analogs showed narcotic antagonist activity when tested against methadone.     

A novel method to prepare highly encapsulated interferon-alpha-2b containing liposomes for intramuscular sustained release.

A novel modified film-hydration-dilution method was employed to prepare highly encapsulated interferon-alpha-2b containing liposomes for intramuscular sustained release. The liposomes produced by this technique were a mixture of mainly unilamellar vesicles and a small number of multilamellar vesicles. The trapping efficiency was above 80%. With at least 60-fold dilution, Triton X-100 at the concentration of 0.3% (w/v) in phosphate buffered saline (PBS) was able to solubilize phospholipids without denaturing the protein and/or interfering with the enzyme-linked immunoassay (ELISA). After three homogenization cycles under a pressure of 70 MPa the size of liposomes was reduced from 978 to 101 nm while the activity of interferon-alpha-2b decreased by 9.9% compared to the control. Although liposomes were physically stable for 22 months at 4 degrees C the mean size of the liposomes increased slightly from 101 to 122 nm. The levels of free interferon-alpha-2b at the site of intramuscular injection decreased rapidly with only 4.15% of initial dose retained at the injection site after 0.33 h following injection of an interferon-alpha-2b solution (nonencapsulated). In contrast, interferon-alpha-2b encapsulated in liposomes was retained at the site of intramuscular injection at higher levels than free interferon-alpha-2b (p < 0.05). Larger liposomes containing interferon-alpha-2b (978 nm) were the most effective for local retention because 27.8% of interferon-alpha-2b was retained after 24 h. These liposomes have the potential to be topically injected for treating genital herpes with prolonged interferon levels at the local injection site. Since the smaller liposomes (75.8 and 101 nm) retained interferon-alpha-2b at the injection site for shorter times while enhancing the blood circulation of the drug, they are potentially good carriers for systemic therapy with higher bioavailability and liver targeting.     

Conformational investigation of α,β-dehydropeptides VII*. Conformation of Ac-Pro-ΔAla-NHCH3 and Ac-Pro-(E)-ΔAbu-NHCH3: comparison with (Z)-substituted α,β-dehydropeptides†

The crystal structure and solution conformation of Ac-Pro-ΔAla-NHCH₃ and the solution conformation of Ac-Pro-(E)-ΔAbu-NHCH₃ were investigated by X-ray diffraction method and NMR, FTIR and CD spectroscopies. Ac-Pro-ΔAla-NHCH, adopts an extended-coil conformation in the crystalline state, with all-trans peptide bonds and the ΔAla residue being in a C₅ form, φ₁=– 71.4(4), ψ₁=– 16.8(4), φ₂=– 178.4(3) and ψ₂= 172.4(3)°. In inert solvents the peptide also assumes the C₅ conformation, but a γ-turn on the Pro residue cannot be ruled out. In these solvents Ac-Pro-(E)- ΔAbu-NHCH₃ accommodates a βII-turn, but a minor conformer with a nearly planar disposition of the CO—NH and C=C bonds (φ₂～0°) is also present. Previous spectroscopic studies of the (Z)-substituted dehydropeptides Ac-Pro-(Z)- ΔAbu-NHCH, and Ac-Pro-ΔVal-NHCH₃ reveal that both peptides prefer a βII-turn in solution. Comparison of conformations in the family of four Ac-Pro-ΔXaa-NHCH₃ peptides let us formulate the following order of their tendency to adopt a β-turn in solution: (Z)- ΔAbu > (E)- δAbu > ΔVal; ΔAla does not. None of the folded structures formed by the four compounds is stable in strongly solvating media. © Munksgaard 1996.     

Elevation of serum 17-β-estradiol in channel catfish following injection of 17-β-estradiol, ethynyl estradiol, estrone, estriol and estradiol-17-β-glucuronide

17-β-Estradiol is naturally converted in numerous organisms to various derivatives/metabolites, which may be excreted from the organism into its immediate external environment. There is a paucity of data regarding the biological effects of these derivatives/metabolites on aquatic organisms. Male channel catfish (200–500 g, N=5, 12–18 months) were injected with 1 mg/kg 17-β-estradiol (E2), ethynyl estradiol (EE2), estrone, estriol or E2-17-β-glucuronide with subsequent measurements of vitellogenin (Vtg) and serum E2 concentrations 7 days post injection. EE2 and E2 gave the largest magnitude of Vtg response followed by estrone and estriol. Exposure to EE2, estrone, and E2-17-β-glucuronide all induced significant increases in serum E2 concentrations. This study indicates that metabolites of E2 are also estrogenic and may potentially disrupt estrogen feedback loops within aquatic organisms.     

Analogs of arginine vasopressin modified in position 3 with (R)-α- hydroxymethylphenylalanine

Abstract: This study describes the synthesis and some pharmacological properties of three new analogs of arginine vasopressin (AVP) substituted in position 3 with (R)-α-hydroxymethylphenylalanine ([R]-HmPhe). All new peptides were tested for vasopressor and antidiuretic as well as uterotonic activity. None of the 3 analogs showed any pressor activity and their uterotonic activity was negligible. Only analog [Mpa¹,(R)-HmPhe³]AVP exhibited significant antidiuretic activity.     

Conformational investigation of α,β-dehydropeptides. IX. N-Acetyl-(E)-α,β-dehydrobutyrine N′-methylamide: stereoelectronic properties from infrared and theoretical studies*

Abstract: : The Fourier transform infrared spectra of Ac-(E)-ΔAbu-NHMe were analyzed to determine the predominant solution conformation (s) of this (E)-α,β-dehydropeptide-related compound and the electron density perturbation in its amide groups. The measurements were performed in dichloromethane and acetonitrile in the region of mode v_s (N–H), amide I, amide II and v_s (C^α= C^β). The equilibrium geometrical parameters, calculated by a method based on the density functional theory with the B3LYP functional and the 6–31G* basis set, were used to support spectroscopic interpretation and gain some deeper insight into the molecule. The experimental and theoretical data were compared with those of three previously described molecules: isomeric Ac-(Z)-ΔAbu-NHMe, Ac-ΔAla-NHMe, which is deprived of any β-substituent, and saturated species Ac-Abu-NHMe. The titled compound assumes two conformational states in equilibrium in the DCM solution. One conformer is extended almost fully and like Ac-ΔAla-NHMe is C₅ hydrogen-bonded. The other adopts a warped C₅ structure similar to that of Ac-(Z)-ΔAbu-NHMe. The C₅ hydrogen bond, unlike the H-bond in Ac-ΔAla-NHMe, is disrupted by acetonitrile. The resonance within the N-terminal amide groups in either of the (E)-ΔAbu conformers is not as well developed as the resonance in Ac-Abu-NHMe. However, these N-terminal groups, compared with the other unsaturated compounds, constitute better resonance systems in each conformationally related couple: the C₅ hydrogen-bonded Ac-(E)-ΔAbu-NHMe/Ac-ΔAla-NHMe and the warped C₅ Ac-(E)-ΔAbu-NHMe/Ac-(Z)-ΔAbu-NHMe. The resonance within the C-terminal groups of the latter couple apparently is similar, but less developed than the resonance in Ac-Abu-NHMe. The electron distribution within the C-terminal group of the hydrogen-bonded C₅ (E)-ΔAbu conformer apparently is determined mainly by the electron influx from the C^α= C^β double bond.     

[7-Methyltryptophan 9] -β-corticotropin-(1–24): a hyperactive Synacthen analogue

[7-Methyltryptophan 9] -β-corticotropin-(1–24) has been synthesised. In an isolated adrenal cell bioassay, it had 2.7 times the steroidogenic activity of β-corticotropin-(1–24) (Synacthen).     

Synthesis of N-(4-aminobenzoyl)-γ-oligo (L-glutamic acid)s*

N-(4-aminobenzoyl)-γ-oligo (l -glutamic acid)s (6) containing from two to six glutamic residues have been prepared in solution using Nα-Boc-α-Bzl protections and isobutyl-chlorocarbonate activation. Key steps in the synthesis were the coupling of γ-oligo(α-benzyl l -glutamate) benzyl esters (1) with N-(4-benzyl-oxycarbonylaminobenzoyl)-l -glutamic acid α-benzyl ester (4) to blocked precursors of N-(4-aminobenzoyl)-γ-oligo (l -glutamic acid)s (5) and catalytic hydrogenolysis of 5 to 6. Elaboration of the required oligo γ-l -glutamate chains (1) was achieved step by step beginning with the coupling of glutamic acid dibenzylester with N-(t-butoxycarbonyl)-l -glutamic acid α-benzyl ester (2) to 3 followed by selective removal of the Boc from 3 with HCl-dioxane followed by coupling with 2.     

β-Endorphin-(1–27) inhibits the spinal beta-endorphin-induced release of Met-enkephalin

The effect of intraventricular β-endorphin-(1–27) on the spinal release of Met-enkephalin induced by intraventricular β-endorphin was studied using the intrathecal superfusion technique in urethane anesthetized rats. Intraventricular injection of β-endorphin at a dose of 15 μg released Met-enkephalin from the spinal cord. This release of Met-enkephalin induced by β-endorphin was significantly reduced by β-endorphin-(1–27), 60 μg, injected intraventricularly. Injection of β-endorphin (1–27) itself did not cause any release of Met-enkephalin. The finding is in line with the previous report that β-endorphin (1–27) inhibited the analgesia induced by β-endorphin.     

Intracellular delivery of doxorubicin with RGD-modified sterically stabilized liposomes for an improved antitumor efficacy: in vitro and in vivo

Passive targeting by sterically stabilized liposomes (SSL), once combined with efficient intracellular delivery, may be a very useful strategy to improve the antitumor efficacy for the anticancer agents. The arginine-glycine-aspartic acid tripeptide (RGD) is known to serve as a recognition motif for several different integrins located on cell surface. In this study, the RGD tripeptide was coupled to the distal end of the poly (ethylene glycol)-coated liposomes (RGD-SSL) aimed to achieve increased tumor accumulation and enhanced intracellular uptake. DOX-loaded RGD-SSL (RGD-SSL-DOX), DOX-loaded SSL (SSL-DOX), and free DOX were compared with respect to their in vitro uptake and cytotoxicity and their in vivo biodistribution and therapeutic efficacy in tumor-bearing mice. Flow cytometry and confocal microscopy studies revealed that RGD-SSL could facilitate the DOX uptake into melanoma cells by integrin-mediated endocytosis. RGD-SSL-DOX displayed higher cytotoxicity on melanoma cells than SSL-DOX. While RGD-SSL-DOX demonstrated prolonged circulation time and increased tumor accumulation as SSL-DOX did, it showed remarkably higher splenic uptake than SSL-DOX. Mice receiving RGD-SSL-DOX (5 mg DOX/kg) showed effective retardation in tumor growth compared with those receiving same dose of SSL-DOX, free DOX solution, or saline. These results suggest that RGD-modified SSL may be a feasible intracellular targeting carrier for efficient delivery of chemotherapeutic agents into tumor cells.     

Practical preparation and deblocking conditions for N-α-(2-(P-biphenylyl)-2-propyloxycarbonyl)-amino acid (N-α-Bpoc-Xxx-OH) derivatives

Reproducible preparations are given for salts of the following L-amino acid derivatives: Bpoc-Ala-OH, Bpoc-Arg(Mtr)-OH, Bpoc-Asn-OH, Bpoc-Asp(OtBu)-OH, Bpoc-Cys(Acm)-OH, Bpoc-Cys(S-tBu)-OH, Bpoc-Gln-OH, Bpoc-Glu(OtBu)-OH, Bpoc-Gly-OH, Bpoc-Ile-OH, Bpoc-Leu-OH, N-α-Bpoc-Lys(ε-Boc)-OH, Bpoc-Met-OH, Bpoc-Phe-OH, Bpoc-Pro-OH, Bpoc-Ser(OtBu)-OH, Bpoc-Thr(OtBu)-OH, Bpoc-Tyr-OH, Bpoc-Val-OH. A study of the deblocking of N-α-Bpoc peptides in dichloromethane containing 0.5% trifluoroacetic acid revealed that a rapid equilb-rium is established between the first-formed monomeric alkene 2-p-biphenylylpropene and the hindered dimer 2,4-bis(p-biphenylyl)-4-methyl-l-pentene. Thioethers were found to be inefficient carbocation scavengers for the deblocking reaction. The most efficient scavengers were found to be thiophenol and benzyl mercaptan, and the following approximate reactivity order was established: benzyl mercaptan ～ thiophenol 〉 indole 1,3-dimethoxybenzene ～ resorcinol 〉1,3,5-trimethoxybenzene ～ dimethyl sulfide ～ thioanisole.     

Comparative Study on Inclusion Complexation of Maltosyl-β-cyclodextrin,Heptakis(2,6-di-O-methyl)-β-cyclodextrin and β-Cyclodextrin with Fucosterol in Aqueous and Solid State

Abstract— The complexation of fucosterol with three kinds of β-cyclodextrin (β-CyD) was investigated in aqueous solution and in the solid state. The solubility of fucosterol increased significantly on its complexation with maltosyl-β-CyD and heptakis(2,6-di-O-methyl)-β-CyD (DM-β-CyD), while no appreciable increase was observed when complexed with β-CyD. The stability constant of complexation with β-CyD estimated from solubility determinations was greater for a 1:2 complex than for a 1:1 complex. On the other hand, 1:1 complexation of fucosterol with maltosyl-β-CyD or DM-β-CyD was greater than 1:2 complexation. The solid complexes were obtained in molar ratios of 1:2 and 1:3 for β-CyD and maltosyl-β-CyD complexes, respectively. The inclusion behaviour of fucosterol with maltosyl-β-CyD was compared with β-CyD in the solid state using DSC, powder X-ray diffractometry and CP/MAS ¹³C NMR. Maltosyl-β-CyD showed different inclusion behaviour compared with β-CyD, and produced an amorphous structure of fucosterol on complex formation. The dissolution rate of fucosterol-maltosyl-β-CyD complex was significantly faster than other complexes due to its high aqueous solubility and amorphous structure.     

The Disposition of (R)-α-Methylhistamine,a Histamine H3-Receptor Agonist,in Rats

Abstract— Using a modified HPLC method with a fluorescence spectrophotometer and a weak cation exchanger, it was possible to separate (R)-α-methylhistamine (α-methylhistamine) from histamine in plasma and various tissues. The assay was used to study the disposition and pharmacokinetic analysis of α-methylhistamine after a bolus intravenous administration to rats. After rapid intravenous administration (12·6 mg kg^?1), the plasma concentration declined biexponentially with a half-life of 1·3 min in the elimination phase. The area under the plasma concentration-time curve and total body clearance were 130 μg min mL^?1 and 97 mL min^?1 kg^?1, respectively. After administration, α-methylhistamine was immediately transferred to various tissues. The concentration was high in the kidney, lung, and liver (kidney > lung > liver), but low in the brain. The tissue-to-plasma concentration ratios in peripheral tissues were greater than 1, suggesting that the transfer of α-methylhistamine to peripheral tissues was due to a specialized transport mechanism or possibly to tissue binding. However, the finding that the tissue/plasma ratio in the brain was lower than unity suggests that the transport system in this tissue depends on a concentration gradient, and that α-methylhistamine crosses the blood-brain barrier in rats with difficulty.     

SYNTHESIS OF N-ACETYL-MURAMYL-l-ALANYL-d-GLUTAMIC-α-AMIDE(MDP) OR -α-METHYL ESTER DERIVATIVES,BEARING A LIPOPHILIC GROUP AT THE C-TERMINAL PEPTIDE END

We report the synthesis of nine lipophilic derivatives of N-acetyl-muramyl-l -alanyl-d -glutamic-α-amide (MDP) or -α-methyl ester in which the γ-carboxyl function of the d -glutamyl residue is either esterified by a medium chain alcohol or substituted by an l -alanyl residue esterified by a medium or long chain alcohol. A new method is described which easily allows one to obtain derivatives of MDP, bearing a free or substituted amino-acyl or peptidyl residue on the γ-carboxyl function.