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A Makriyannis

Publications and source records attributed to A Makriyannis.

At least 109 records · Page 6Linked to original sources
PubMed1995

Classical/non-classical cannabinoid hybrids; stereochemical requirements for the southern hydroxyalkyl chain.

We have synthesized a range of hybrid classical/non-classical cannabinoids (CC/NCCs) combining the hexahydrocannabinol dibenzopyran structure with the hydroxyalkyl chain found in CP-55940, in order to investigate the role of the hydroxyalkyl pharmacophore in cannabimimetic activity. This was achieved by synthesizing CC analogs in which the 6 alpha- and 6 beta-methyl groups were modified to the corresponding hydroxyethyl groups. Our binding data indicated that beta position was the preferred orientation for the hydroxyalkyl moiety, affinity for the CB1 receptor being 20-fold greater for the 6 beta-hydroxyethyl than the corresponding 6 alpha-analog. Further studies using 6 beta-hydroxyalkyldibenzopyran analogs varying the southern aliphatic chain length from 6 beta-hydroxymethyl to 6 beta-hydroxyethyl to 6 beta-hydroxypropyl demonstrated little potency change with chain length. Therefore, we concluded that whilst the hydroxyalkyl pharmacophore was strongly affected by its configuration relative to the dibenzopyran ring, the chain length of the hydroxyalkyl moiety (up to the n = 3 homolog) was not critical.

Animals↗
PubMed1994

Syntheses of racemic and nearly optically pure ether lipids and evaluation of in vitro antineoplastic activities.

In addition to rac-2-O-methyl-1-O-octadecylglycero-3-phosphocholine (rac-ET-18-OCH3, rac-Edelfosine, 1), three racemic ether lipid analogs, 4, 5, and 6, were synthesized where N,N-dimethylamino, N-methylpyrrolidino, and N-methylmorpholino groups, respectively, have been substituted for the trimethylammonio group. The two enantiomers, (R)-ET-18-OCH3 (2) and (S)-ET-18-OCH3 (3), and all four possible chiral methylcholine analogs, 7, 8, 9, and 10, of (R)-ET-18-OCH3 (2) were also synthesized. Three human leukemic cell lines (CEM, HUT 78, and Namalwa) were used to assess the in vitro antineoplastic properties of these 10 ether lipid analogs. At ether lipid concentrations of 5-50 micrograms/mL, dose- and time-dependent cytotoxicities were demonstrated up to 24 h. CEM and HUT 78, both T cell derived, were more sensitive to the ether lipids than Namalwa, which is B cell derived. rac-ET-18-OCH3 (1) with its R and S enantiomeric forms, 2 and 3, respectively, exhibited modest stereoselectivity in HUT 78 and Namalwa with 1 and 2 slightly more cytotoxic than 3. Ether lipid (EL) analogs 4, 5, and 6 demonstrated significantly greater cytotoxicity in normal peripheral lymphocytes, 4 and 6 exhibited a modest increase in cytotoxicity in HUT 78 and Namalwa (P < 0.05), and 5 demonstrated greater cytotoxicity (P < 0.05) in Namalwa than the parent EL 1. The calculated 24 h ID50 values suggest that the beta-methyl analogs, 9 and 10, were more cytotoxic than the alpha-methyl analogs, 7 and 8, in all the tested cancer cell lines.

Antineoplastic Agents↗
PubMed1994

Chiral resolution of 1,3-dimethyl-4-phenylpiperidine derivatives using high-performance liquid chromatography with a chiral stationary phase.

A number of racemic 1,3-dimethyl-4-phenylpiperidines which serve as intermediates in the synthesis of opioid analgesics have been resolved on two commercially available high-performance liquid chromatography columns containing cellulose-based chiral stationary phases: Chiralcel OD and Chiralcel OJ. The resolution results were complementary between the two columns. Also, the polarity of substituents appears to play an important role on the ability of the Chiralcel OD column to resolve pairs of enantiomers.

Alphaprodine↗
PubMed1994

Topography of alphaxalone and delta 16-alphaxalone in membrane bilayers containing cholesterol.

We have used small-angle X-ray diffraction and differential scanning calorimetry (DSC) to study the topographies of alphaxalone and its biologically inactive analog delta 16-alphaxalone in dimyristoylphosphatidylcholine (DMPC) and DMPC/cholesterol model membranes. Diffraction patterns were obtained and analyzed for preparations of bilayers without and with the steroids. Temperature dependence of the total period repeat distance (d-spacing) allowed us to identify equivalent temperatures at which the preparations had similar d-spacing and were in the same mesomorphic state. The combination of X-ray and DSC data showed that the anesthetic steroid alphaxalone broadens the membrane phase transition and increases the ratio of gauche: trans conformers in the membranes in contrast to the inactive steroid delta 16-alphaxalone which affects the membranes only marginally. In model DMPC membranes alphaxalone and delta 16-alphaxalone are located near the bilayer interface. This location is maintained by alphaxalone when cholesterol is incorporated in the bilayer as evidenced by the X-ray measurements. However, when delta 16-alphaxalone is incorporated in cholesterol containing bilayers, a decrease in the electron density profile of the preparation is observed. This can be explained by invoking the formation of a delta 16-alphaxalone-cholesterol complex. The delta 16-alphaxalone complex shows no periodicity and is therefore, not detected in the X-ray diffraction experiment. Presumably, this complex forms aggregates either on the surface or inside the bilayer. This explanation corroborates DSC results which show that delta 16-alphaxalone sharpens the phase transition of DMPC/cholesterol preparations, an indication that some cholesterol is excluded from the bilayer preparation after the addition of the biologically inactive steroid.

Anesthetics↗
PubMed1994

Structure and orientation of the pore-forming peptide, melittin, in lipid bilayers.

Ten analogues of the 26-residue, bee venom peptide, melittin (H3N(+)-GIGAVLKVLTTGLPALISWIKRKRQQ-CONH2), were synthesized, each with 13C enrichment of a single peptide carbonyl carbon. These peptides were incorporated into bilayers of the diether lipid, ditetradecylphosphatidylcholine, aligned between stacked glass plates. Solid-state 13C nuclear magnetic resonance spectra were obtained as a function of the angle between the bilayer planes and the magnetic field of the spectrometers, and at temperatures above and below the lipid gel-to-liquid crystalline transition temperature, Tc. For bilayers aligned with the normal along the applied magnetic field there was no shift in the carbonyl resonances of residues Ile2, Ala4, Leu9, Leu13, or Ala15, with minor changes for residues Val8 and Ile20, and small changes at Val5, Leu6 and Ile17 on immobilization of the peptide below Tc. In contrast, the spectra for bilayers aligned at right angles to the field showed greatly increased anisotropy below Tc for all analogues. From these experiments it was evident that the peptide was well-aligned in the bilayers and reoriented about the bilayer normal. The observed reduced chemical shift anisotropies and the chemical shifts were consistent with melittin adopting a helical conformation with a transbilayer orientation in the lipid membranes. With the exception of Ile17, there was no apparent difference between the behaviour of residues in the two segments that form separate helices in the water-soluble form of the peptide, suggesting that in membranes the angle between the helices is greater than the 120 degrees observed in the crystal form.

Amino Acid Sequence↗
PubMed1994

Synthesis and pharmacological properties of 11-hydroxy-3-(1',1'-dimethylheptyl)hexahydrocannabinol: a high-affinity cannabinoid agonist.

11-Hydroxy-3-(1',1'-dimethylheptyl)hexahydrocannabinol (1) was synthesized from the known cannabimimetic analog (+/-)-nabilone. Racemic 1 was resolved by HPLC on a semipreparative CHIRALCEL OD column (Daicel, Inc.), and pharmacological activities of the individual enantiomers were evaluated in the mouse model. The (-)-enantiomer was found to be much more potent than the (+)-enantiomer in all the four measures with the potency ratios in the production of catalepsy (RI), hypoactivity (SA), hypothermia (RT), and antinociception (TF) being 93, 143, 186, and 322, respectively. The racemic 11 alpha-OH diastereomer (2), a reaction side product, was also evaluated in the mouse model. Only small differences in the pharmacological activity of racemic 1 and 2 were found in the above four measures.

Analgesia↗
PubMed1994

(R)-methanandamide: a chiral novel anandamide possessing higher potency and metabolic stability.

Four chiral congeners of arachidonylethanolamide (anandamide) have been synthesized and evaluated for (a) their ability to bind to the cannabinoid receptor in rat forebrain membranes and (b) their pharmacological potency as measured by the compounds' ability to inhibit electrically-evoked contractions of the mouse vas deferens. The lead analog was also tested for its potency in vivo. Of the analogs tested, (R)-(+)-arachidonyl-1'-hydroxy-2'-propylamide [(R)-methanandamide] exhibited the highest affinity for the cannabinoid receptor with a Ki of 20 +/- 1.6 nM, 4-fold lower than that of anandamide (Ki = 78 +/- 2 nM). Moreover, determination of the cannabinoid binding affinity in the presence and absence of the protease inhibitor phenylmethanesulfonyl fluoride (PMSF) revealed that (R)-methanandamide possesses a remarkable stability to aminopeptidase hydrolysis. Pharmacological studies on mouse isolated vasa deferentia demonstrated that all four analogs produce concentration-related inhibition of the twitch response and the order of potency is the same as the rank order of the affinities of these agonists for cannabinoid binding sites. Furthermore, experiments with mice have demonstrated that (R)-methanandamide also possesses cannabimimetric properties in vivo, as established by the four tests of hypothermia, hypokinesia, ring immobility, and antinociception.

Aminopeptidases↗
PubMed1994

Conformational analysis of the prototype nonclassical cannabinoid CP-47,497, using 2D NMR and computer molecular modeling.

In an effort to determine the stereochemical requirements for pharmacological activity among the series of nonclassical cannabinoids synthesized at Pfizer, we have studied the conformational properties of the parent bicyclic analog CP-47,497. For this study, we have used a combination of solution NMR and theoretical computational approaches. The energetically favored conformation has the phenolic ring almost perpendicular to the cyclohexanol ring which exists in a chair conformation. The OH bond of the phenol is preferentially coplanar with the aromatic ring and points toward the C2 ring proton, while the dimethylheptyl side chain adopts a conformation almost perpendicular to the aromatic ring. The conformational features of this nonclassical cannabinoid analog closely resemble those of its classical counterparts. The only apparent difference is the small dihedral angle (psi 1 = 62 degrees) between the planes of the two rings of CP-47,497 compared to that of the tricyclic tetrahydro- or hexahydrocannabinol analogs (psi 1 = 137 degrees). However, CP-47,497 can be perfectly superimposed over the respective tricyclic analog by rotation around the Ph-cyclohexyl bond (C6-C7 bond) and assume a conformation which is energetically higher than the preferred one by 3.0 kcal/mol. It can be argued that such a conformation may be acquired by the nonclassical analog during its interaction with the active site.

Cannabinoids↗
PubMed1994

Role of the NH2-terminal domain of angiotensin II (ANG II) and [Sar1]angiotensin II on conformation and activity. NMR evidence for aromatic ring clustering and peptide backbone folding compared with [des-1,2,3]angiotensin II.

The role of the NH2 termini of angiotensin II (ANG II) and [Sar1]ANG II on conformation and activity were examined by proton NMR two-dimensional-J-correlated spectroscopy and one-dimensional nuclear Overhauser effect studies in the relatively nonpolar "receptor-simulating" environment provided by dimethyl sulfoxide-d6, using the biologically inactive COOH-terminal pentapeptide [des1,2,3]ANG II as control. Irradiation of C alpha H, C2H, and C4H proton resonances in ANG II and [Sar1]ANG II resulted in enhancements of Tyr and Phe ring proton resonances, indicating that the three aromatic rings cluster together. Very strong enhancements (17-22%) of the C alpha Y proton resonance in ANG II and [Sar1]ANG II upon irradiation of the C alpha H proton resonance, and vice versa, revealed that a Tyr-Ile-His bend is a predominant feature of the conformation of the two agonists. In contrast, saturation of the C alpha H and C alpha Y proton resonances in the control pentapeptide [des-1,2,3]ANG II did not produce, respectively, any C alpha Y or C alpha H proton nuclear Overhauser effect enhancement, illustrating the absence of a Tyr-Ile-His bend in the truncated ANG II peptide. The present findings indicate that the NH2-terminal domain of ANG II appears to have an essential role in generating the biologically active charge relay conformation of the hormone.

Algorithms↗
PubMed1993

Topography of tetrahydrocannabinol in model membranes using neutron diffraction.

Small-angle neutron scattering was used to determine the intralamellar location of (-)-delta 8-tetrahydrocannabinol (delta 8-THC) in hydrated dipalmitoylphosphatidylcholine (DPPC) bilayers. Nuclear scattering density profiles were calculated from measurements on deuterium and non-deuterium-labelled inclusions (8.3% (w/w)) of delta 8-THC in DPPC multilayer samples. By comparing pairs of such nuclear density profiles, the locations of the deuterium labels were determined. Present results on the topography of delta 8-THC in membranes are compared with earlier X-ray measurements using iodine labelling. Whereas the position of the phenolic hydroxy group is similar in both types of measurement, a difference is found in the conformation of the terminal methyl groups of the cannabinoid side-chains. The X-ray measurements on dimyristoylphosphatidylcholine (DMPC) indicated that the iodine-labelled cannabinoid side-chains assume an all-trans orientation with the terminal iodine atom pointing inward into the membrane away from the tricyclic region while the neutron measurements indicate that the terminal CH3 group of delta 8-THC aligns itself at the level of the tricyclic ring system implying that the side chain exists in a more compact conformation perpendicular to the DPPC hydrocarbons. A Gaussian function analysis of the data indicates that the delta 8-THC molecule is significantly delocalized in the DPPC membrane in the liquid crystal phase. The mean location of delta 8-THC suggests that the active site on a membrane-embedded receptor protein will lie near the polar interface at the base of the phospholipid headgroups.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1993

Small angle X-ray diffraction studies of (-)-delta 8-tetrahydrocannabinol and its O-methyl analog in membranes.

Small angle X-ray diffraction was used to study the topography of (-)-delta 8-tetrahydrocannabinol (delta 8-THC) and its pharmacologically inactive methoxy analog (-)-O-methyl-delta 8-tetrahydrocannabinol (Me-delta 8-THC) in a membrane. The membrane preparations were partially hydrated dimyristoylphosphatidylcholine (DMPC) bilayers. Comparisons between electron density profiles from the drug-containing and drug-free membranes showed that the amphipathic delta 8-THC residues near the interface of the bilayer where the polar phenolic OH of the drug molecule is oriented towards the corresponding polar side of the phospholipid bilayer. Conversely, the highly hydrophobic Me-delta 8-THC distributes deeper in the bilayer away from the interface. Our results point out these two structurally-related, but pharmacologically very different, cannabinoids interact with membranes in strikingly different manners. This observation may, in part, explain the different pharmacological properties of the two cannabinoids.

Dronabinol↗
PubMed1993

Pharmacological evaluation of iodo and nitro analogs of delta 8-THC and delta 9-THC.

One aspect of cannabinoid structure-activity relationships (SARs) that has not been thoroughly investigated is the aromatic (A) ring. Although halogenation of the side chain enhances potency, our recent observation that iodination of the A ring also enhanced activity was surprising. The purpose of this investigation was to establish the steric and electrostatic requirements at these sites of the cannabinoid molecule via molecular modeling, while determining pharmacological activity. Molecular modeling was performed using the Tripos molecular mechanics force field and the semiempirical quantum mechanical package AM1. The Ki values for novel cannabinoids were determined in a [3H]CP-55,940 binding assay and ED50 values generated from four different evaluations in a mouse model. The present studies underscore the increase in potency produced by a dimethylheptyl (DMH) side chain. Trifluoro substitutions on the pentyl side chain, or bromination of the DMH side chain, had little effect on the pharmacological activity. Any substitution at the C4 position of the aryl ring resulted in a loss of activity, which appears to be due to steric hindrances. Nitro, but not iodo, substitution at the C2 position essentially produces an inactive analog, and the drastic alteration of the electrostatic potential appears to be responsible. The altered pharmacological profile of the 2-iodo analog seems to be related to an alteration in the highest occupied molecular orbital because there is no alteration in the electron density map compared to delta 8-tetrahydrocannibinol.

Analgesics↗
PubMed1993

Conformational analysis of the opioid phenylmorphan and its 9 alpha-methyl analogue in solution using high-resolution nuclear magnetic resonance spectroscopy.

The solution conformations of the opioid phenylmorphan (5-m-hydroxyphenyl-2-methylmorphan) and its 9 alpha-methyl analogue were studied using one- and two-dimensional high resolution NMR techniques. The NMR spectra were analyzed by interpreting the phase-sensitive 2-D COSY and double quantum filtered COSY spectra, 1H-1H vicinal coupling constants, and nuclear Overhauser effects in the phase-sensitive 2-D NOESY spectra. The results show that, for both compounds, a chair-chair conformation of the cyclohexane and piperidine rings is exclusively preferred with some distortion of the rings from perfectly staggered chairs. For phenylmorphans, the phenyl ring is oriented to fit into the cleft formed by the cyclohexane and piperidine rings. Thus, for the (+)-enantiomer, the phenyl group assumes the same orientation with regard to the piperidine ring as morphine consistent with the morphine-like properties of the compound. For the 9 alpha-methyl analogue, the plane of the phenyl ring essentially bisects the piperidine ring to which it is attached and is outside of the required range of opioid agonists. This is consistent with the atypical properties of the two enantiomers. The NMR results are compared to the conformations of (-)-phenylmorphan and the (+)-9 alpha-methyl analogue in the crystal state and to the results of molecular mechanics (MM2) studies.

Ligands↗
PubMed1993

Hallucinogenic receptor models: interaction of imidazolium chloride with amphetamine analogs.

The interactions of several hallucinogenic phenethylamines with the biologically relevant electron acceptor imidazolium chloride have been investigated by monitoring phenethylamine 1H NMR chemical shift changes upon complex formation. Methoxy- and methylenedioxy-substituted phenethylamines interact with imidazolium chloride to form weak charge-transfer complexes that have a relatively narrow range of association constants. The results indicate the formation of a ternary complex in which a chloride ion is hydrogen bonded to a N+H side chain proton of the drug and a NH imidazolium proton. The imidazolium ring is positioned above a nonsubstituted ortho-position of the aromatic ring. Spectral assignment of the two diastereotopic benzylic protons allowed the geometry of the complex to be defined in more detail. Complexation occurs preferentially on that side of the phenethylamine molecule that allows the side chain alpha-methyl group to face away from the chloride ion and the imidazolium ring. The drug molecule exists in the complex in the preferred trans conformation. The biological relevance of this model is discussed.

Amphetamines↗
PubMed1992

Conformational preferences of the kappa-selective opioid agonist U50488. A combined molecular mechanics and nuclear magnetic resonance study.

The conformational preferences of the kappa-selective opioid agonist U50488 have been studied using MM2-87 calculations and nuclear magnetic resonance (NMR) spectroscopy. The calculations were performed for the protonated form with a dielectric constant of 80 and the unprotonated form with dielectric constants of 1.5 and 80. A systematic search found 72 stable conformers with certain consistent conformational preferences for some of the important dihedral angles. The preferred conformers proved to be compact structures stabilized by intramolecular attractive van der Waals interactions, though at least some of these appear to be electrostatically unfavorable. The conformation of U50488 was also examined in aqueous solution using one-dimensional (1D) and two-dimensional (2D) high-resolution 1H NMR techniques such as the interpretation of 1H-1H vicinal coupling constants, 1D and 2D nuclear Overhauser effect (NOE) experiments, and 2D correlated spectroscopy (COSY) experiments. Five crystallographic conformations were examined as well. There was generally good agreement between all three methods of conformational analysis. There appeared to be a reasonable geometrical agreement between the relatively rigid kappa-agonist (-)-ketazocine and a gauche conformer of U50488. The proposed pharmacophore is also consistent with other kappa-selective analogs of U50488 including one in which the peptide bond is incorporated into a lactam ring. The low affinity of U50488 for mu-receptors was attributed to its cyclohexane ring which occupies space not present in the nonselective (-)-ketazocine.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗