A novel µ-opioid receptor ligand with high in vitro and in vivo agonist efficacy.

The aims of this study were to synthesize 14-O-Methylmorphine-6-O-sulfate (14-O-MeM6SU) and examine its opioid properties (potency, affinity, efficacy) in receptor ligand binding and isolated tissues (mouse vas deferens, MVD and rat vas deferens, RVD bioassays). The results were then compared to the parent compounds morphine-6-O-sulfate (M6SU) and morphine, as well as the �- opioid receptor (MOR) selective agonist peptide [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO). An additional objective was to compare the effect of subcutaneously (s.c.) or intracerebroventricularly (i.c.v.) administered 14-O-MeM6SU, M6SU and morphine in thermal nociception, rat tail-flick (RTF) test. In MVD, the EC50 (nM) value was 4.38 for 14-O-MeM6SU, 102.81 for M6SU, 346.63 for morphine and 238.47 for DAMGO. The effect of 14-O-MeM6SU and DAMGO was antagonized by naloxone (NAL) with Ke value 1-2.00 nM. The Emax values (%) were 99.10, 36.87, 42.51 and 96.99 for 14-O-MeM6SU, M6SU, morphine and DAMGO, respectively. In RVD 14-O-MeM6SU and DAMGO but not M6SU or morphine showed agonist activity. In binding experiments the affinity of 14-OMeM6SU, M6SU, morphine and DAMGO for MOR was 1.12, 11.48, 4.37 and 3.24 nM, respectively. The selectivity of 14-O-MeM6SU was κ/µ= 269 and δ/µ= 9. In G-protein activation experiments, 14-O-MeM6SU and DAMGO showed higher Emax values than M6SU or morphine. S.c. or i.c.v-injected 14-O-MeM6SU, M6SU and morphine produced a dose and time-dependent increase in RTF response latency. 14-O-MeM6SU was the most potent. Our results showed that introduction of 14-O-Me in M6SU increased the binding affinity, agonist potency, and most importantly, the intrinsic efficacy (Emax).

Structural and physicochemical profiling of morphine and related compounds of therapeutic interest.

A concise account of the physicochemical properties of morphine and its derivatives of therapeutic interest is provided. Such properties include macroscopic and microscopic acid/base parameters, lipophilicity, solubility, permeability that all influence the fate of drugs in the body. The dependence of these parameters on pH is discussed and subsequent implications in drug administration and formulation are presented.

The chemical and pharmacological importance of morphine analogues.

The object of this review is to summarize the efforts which resulted in the discovery of therapeutically useful morphine-like drugs. The search for new analgesics can be divided into three stages: (a) search for analgesics with high efficacy and reduced unwanted side-effects; (b) understanding of structure-activity relationships; (c) studies on the mechanism of pain perception and its alleviation by investigation of the pharmacology of opioids. An immense body of literature has been produced on the syntheses of thousands of new compounds which resulted in the development of detailed structure-activity relationships. The physical and psychologic dependence of opioid analgesics also facilitated investigators to solve the problem of the separation of strong analgesia from addiction liability. In the past decades more mixed agonist-antagonist analgesics, pure antagonists devoid of agonist action and potent opioids like the 6,14-ethenomorphinan derivatives were developed. Naloxone, Naltrexone, Buprenorphine and Pentazocine are the outstanding representatives which are introduced into clinical therapy.

Site-specific acid-base properties of pholcodine and related compounds.

The acid-base properties of pholcodine, a cough-depressant agent, and related compounds including metabolites were studied by 1H NMR-pH titrations, and are characterised in terms of macroscopic and microscopic protonation constants. New N-methylated derivatives were also synthesized in order to quantitate site- and nucleus-specific protonation shifts and to unravel microscopic acid-base equilibria. The piperidine nitrogen was found to be 38 and 400 times more basic than its morpholine counterpart in pholcodine and norpholcodine, respectively. The protonation data show that the molecule of pholcodine bears an average of positive charge of 1.07 at physiological pH, preventing it from entering the central nervous system, a plausible reason for its lack of analgesic or addictive properties. The protonation constants of pholcodine and its derivatives are interpreted by comparing with related molecules of pharmaceutical interest. The pH-dependent relative concentrations of the variously protonated forms of pholcodine and morphine are depicted in distribution diagrams.

6-oxo-morphinane oximes: pharmacology, chemistry and analytical application.

The permanent therapeutic importance of morphine derivatives in pain treatment has inspired continual synthetic efforts to modify the rigid pentacyclic systems in search for new selective analgesic agents. As a result, several morphinane oximes have been synthesized recently, which have the additional advantage of possessing an oxime group that can provide a method for selective determination of opiate alkaloids in biological matrices. The oximes of hydrocodone and oxycodone have stronger analgesic effect than the parent ketones and they also proved to be effective in preventing the respiratory depressant and hypotensive actions of fentanyl. In this work a review is given on the present status of oxime pharmacology, chemistry and analysis and also the oxime and O-methyl oxime formation of 6-oxo-morphinanes with therapeutic interest (codeinone, oxycodone, hydrocodone and 14-OH-codeinone). The oxime formation was monitored by reversed-phase HPLC and the chromatographic properties of oxime isomers have been characterized. The assignation of the individual isomers isolated by preparative HPLC was performed by (1)H NMR spectroscopy based on the chemical shift differences of the 5-H signals. In this way the isomeric ratio in the oxime products could also be determined. It was found that in the case of Delta(7)-6-oxo-morphinanes, depending on the substituents, the formation of the Z-isomer highly dominates (73-96%) over that of the E-isomer. However, for the saturated 7,8-(dihydro) derivatives the E-isomer is definitely preferred (>98%). In conclusion of a survey on the theoretical background of oxime isomerism, the conformational differences between the saturated and unsaturated morphinane systems were found responsible for the different E/Z ratios. On the basis of the isomeric ratio and the on-line CD and UV spectra of the pure isomers, the molar ellipticities and absorbancies of the isomers were calculated by a parameter estimation method.

Effects of structural modifications of N-CPM-normorphine derivatives on agonist and antagonist activities in isolated organs.

The agonistic and antagonistic properties of N-cyclopropylmethyl (N-CPM) morphine derivatives were observed in mouse vas deferens (MVD), longitudinal muscle of guinea pig ileum (GPI) and rabbit vas deferens (LVD). In MVD the K(e) values of the titled compounds (N-CPM-morphine, N-CPM-isomorphine, N-CPM-dihydromorphine, N-CPM-dihydroisomorpPhine, N-CPM-dihydromorphone and naltrexone) were measured for mu-, kappa- and delta-receptors using normorphine, ethylketocyclazocine (EKC) and D-Pen2-D-Pen5-enkephaline (DPDPE) as selective agonists on the receptors, respectively. For mu-receptors of MVD the tested compounds showed similar affinity. For kappa-receptors the non-iso-6-OH derivatives possessed much less affinity than the iso-derivatives. Similar difference could be observed for delta-receptors. The agonistic activities of these compounds in MVD were observed to be between 0-20% of the inhibition of muscle contractions. In GPI the compounds except naltrexone possessed strong agonistic activities effectively antagonized by nor-binaltorphimine (nor-BNI) (K(e) of nor-BNI was 0.23 nM) suggesting that they were strong kappa-receptor agonists. We investigated these agents in LVD too, which contains kappa-receptors, but they did not produce any agonist potencies. It raises the possibility that the kappa-receptor subtypes of LVD and MVD are different from the kappa-receptor subtype of GPI or the vasa deferentia contain much fewer kappa-receptors than GPI and the intrinsic activities of these compounds are too small to reach the 50% inhibition of the contractions.

Determination of 6-oxo-morphinans, as the oximes, by difference circular dichroism spectroscopy.

A negative Cotton effect is observed in the circular dichroism (CD) spectra of 6-oxo-morphinans in the wavelength range of n-pi* electron transitions. 6-oxo-Morphinans can be transformed into oxime derivatives with hydroxylamine and after oxime formation the CD spectra are significantly different. Oxime formation was monitored by CD and by HPLC. It was established that under the experimental conditions used oxime formation was complete within 90 min. The method suggested for the determination of 6-oxo-morphinans is based on the considerable differences between the ellipticities before and after the oxime formation. The ellipticity difference varies linearly with concentration in the range 2 x 10(-5)-5 x 10(-4) mol L(-1) for the three 6-oxo-morphinans examined (oxycodone, hydrocodone, and 14-hydroxycodeinone). For hydrocodone the dependence is also linear in a lower concentration range (5 x 10(-6)-10(-4) mol L(-1)). The new difference CD spectroscopic method can be applied to the selective determination of 6-oxo-morphinans in bulk and dosage forms.

[Heroin. II. Preparation, hydrolysis, stability, pharmacokinetics]. / A heroin. II. Rész: elóállítás, hidrolízis, stabilitás, farmakokinetika.

Heroin is prepared by treating morphine with acetyl chloride or acetic anhydride. It is a simple reaction and the yields are generally quantitative. Nowadays the whole process is illegal. Morphine is the major alkaloid present in the opium poppy. Opium is manufactured illicitly then morphine is extracted from it in clandestine laboratories. Numerous studies were carried out on heroin to investigate its rate of hydrolysis. It has been shown that heroin is rapidly deacylated in aqueous solution at alkaline or acidic pH to form 6-acethylmorphine and finally, to morphine. Heroin also rapidly decomposes in biological medium yielding first 6-acetylmorphine and then morphine. Hydrolysis can be performed in blood and in tissue homogenates. Heroin can be administered by several routes. Smoking and intravenous administration are preferred, but intranasal, intramuscular and subcutaneous administration are also common. Recently, there has been a shift in heroin use patterns from injection to sniffing and smoking. Sharing of the injection equipment can result in several severe infectious diseases, such as AIDS, hepatitis B and C. Soon after administration, heroin metabolizes to 6-acetylmorphine and morphine. Most of the pharmacological activities of heroin are due to these active metabolites. Therefore, knowledge of distribution of 6-acetylmorphine and morphine is essential to understand pharmacological properties of heroin. Heroin, which is relatively nonpolar compound compared with morphine, has high lipid solubility facilitating rapid absorption from the bloodstream and passage through the blood-brain barrier. When heroin is administered by intravenously the drug takes 10 s to reach the brain i.e. pharmacological effects appear quickly.

[The history of heroin]. / A heroin története.

The discovery of heroin and the development of heroin abuse are introduced. Heroin, the hydrochloride of diacetylmorphine, was discovered by acetylation of morphine. Heroin, in pharmacological studies, proved to be more effective than morphine or codeine. The Bayer Company started the production of heroin in 1898 on a commercial scale. The first clinical results were so promising that heroin was considered a wonder drug. Indeed, heroin was more effective than codeine in respiratory diseases. It has turned out, however, that repeated administration of heroin results in the development of tolerance and the patients become heroin-addicts soon. In the early 1910s morphine addicts "discovered" the euphorising properties of heroin and this effect was enhanced by intravenous administration. Heroin became a narcotic drug and its abuse began to spread quickly. Restrictions on its production, use and distribution were regulated by international treties. The total ban on heroin production was also proposed. As a result of the strict regulations the production and cosumption of heroin showed a significant decrease after 1931. At the same time the underworld recognized the shortage of heroin and started the illicit production and trafficking. The quantity of heroin seized by law enforcement agencies in the past decades rose gradually. As an indicator of the worldwide heroin market, the quantity of confiscated heroin underwent a tenfold increase since 1970. The paper surveys the most important heroin-producing and trafficking countries. Heroin, prepared in clandestine ("kitchen" or "jungle") laboratories, is diluted ("cut") by every member of the illegal heroin distributing chain, i.e. smugglers, traffickers, dealers and vendors.

Tritiated kappa receptor antagonist norbinal torphimine: synthesis and in vitro binding in three different tissues.

Recently a new antagonist with high selectivity for the kappa receptors (norbinaltorphimine) was developed and tested in various systems. This compound was radiolabelled with tritium resulting in high specific radioactivity (47.2 Ci/mmol). [3H]Norbinaltorphimine was characterized by in vitro radioligand binding assays. The radioligand binds to kappa-opioid receptors with a high potency and selectivity in guinea pig, frog and rat brain membranes. Our results suggest the kappa1 specificity of the radioligand.

[Synthesis and analytical characterization of the dansyl derivatives of 6,14-ethenomorphinans]. / 6,14-Etenomorfinánok danzil-származékainak szintézise és analitikai jellemzése.

The synthesis of the dansyl derivatives of the pharmacologically important 6,14-ethenomorphinans has not been reported. The authors realized the preparation of the dansyl derivatives (2a-i) of some 20-alkyl(aralkyl)-orvinols (1a-i). The authors unequivocally proved the structure of the parent compounds, and their dansyl derivatives. The authors also investigated certain analitical characteristics (thin-layer chromatography, UV-spectral data and reversed-phase HPLC purity tests) for the detection if necessary of these compound in biological fluid. Namely, due to the fluorescent properties of the dansyl derivatives, the sensitivity and selectivity of the analytical determinations of the parent compounds are significantly enhanced.

Affinity profiles of novel delta-receptor selective benzofuran derivatives of non-peptide opioids.

Highly selective heterocyclic opioid ligands with potent delta-antagonist activity have been developed on the basis of the "message-address" concept. Using this strategy, benzofuran derivatives corresponding to the non-selective opioid antagonist, naloxone, and to the mu-opioid receptor selective agonists, oxymorphone and oxycodone, were synthesized. In vitro opioid receptor binding profiles and agonist/antagonist character of these compounds were determined in rat brain membrane preparations with highly selective radioligands. All three benzofuran derivatives displayed high affinities for the delta-opioid receptor, much less potency toward the mu-binding site, and were the least effective at the kappa-site. The results indicated that the addition of the bezofuran moiety to these fused ring opioids confers delta-receptor selectivity. The Na+ indices suggested a partial agonist character for oxymorphone- and oxycodone-benzofuran, and an antagonist character for naloxone-benzofuran. These compounds were capable of irreversible inhibition of opioid binding sites in a dose-dependent.

The discovery of alkaloids.

This paper presents the history of the discovery of the first alkaloids. Isolation of alkaloids is connected with the study of the active principles of medicines of plant origin, for example opium and cinchona bark. Sertürner described morphine as a plant alkali and claimed that it was capable of neutralizing free acids yielding salts. The recognition of alkaloids as a new class of compounds was an important step at that time because of the dogmatic denial of the possible existence of plant bases. Isolation of alkaloids is a significant event from the point of view of chemistry, physiology and medicine. The discovery caused essential conceptual changes in chemistry. Priority claims with reference to the discovery of the alkaloids are also reviewed.

New nepenthone and thevinone derivatives.

The diastereoselective reaction of thevinone (2a) and nepenthone (2c) and their dihydro derivatives (2b and d) with Grignard reagents afforded new N-substituted (20S)- and (20R)-phenyl-6,14-ethenomorphinan derivatives (6a-y). The Grignard reaction of the N-substituted-N-demethyl derivatives 4a-f and 4m-r with methylmagnesium iodide resulted in the (20R)-phenyl tertiary alcohols 5a-f and 5m-r, respectively, but the conversion of 4g-1 and that of the N-substituted-dihydrothevinone derivatives with phenylmagnesium bromide afforded the (20S)-phenyl derivatives 5g-l and 5s-y, respectively. The N-cyclopropylmethyl-, N-beta-phenylethyl-, and N-propyl derivatives were prepared by the 3-O-demethylation of compounds 5. For the synthesis of the N-allyl-, N-dimethylallyl-, and N-propargyl compounds 2a-d were reacted with the corresponding Grignard reagent, and treatment of the products with cyanogen bromide gave the cyanamides 8a-d. These latter compounds were transformed into 10a, b,d, whose alkylation led to the target derivatives 6d-f, j-l, p-r, and w-y. The biochemical investigation of these substances showed that the affinities to the delta-opioid receptors were high, but the selectivity was low. In two cases (6c and 11d) a mu-opioid receptor specificity was observed.

Endogenous morphine.

This review surveys the discovery of endogenous alkaloids in mammals. The formation of morphine in mammalian brain was assumed in 1970. The existence of morphine was demonstrated by radioimmunoassay. Identification of morphine was performed by spectroscopic methods. The isolation of mammalian morphine raises the question of biosynthesis. Recently, it has been shown that the biosynthetic pathway is similar to that that exists in poppy.

Dihydrocodeinone-hydrazone, dihydrocodeinone-oxime, naloxone-3-OMe-oxime, and clocinnamox fail to irreversibly inhibit opioid kappa receptor binding.

Previous work from our lab identified two subtypes of the opioid kappa receptor. Whereas the kappa1 receptor can be labeled by [3H]U69,593 (5 alpha,7 alpha,8 beta-(-)- N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl]-phenyl- benzeneacetamide), the kappa2 receptor can be labeled by [125I]OXY (6 beta-125iodo-3,14-dihydroxy-17-cyclopropylmethyl-4,5 alpha-epoxymorphinan). Other data demonstrate that [125I]IOXY, like [3H]bremazocine, labels two populations of kappa2 receptors in guinea pig brain: kappa2a and kappa2b binding sites. In the present study, we tested the hypothesis that certain dihydrocodeinone and oxicodone derivatives, which have been shown to irreversibly block low affinity [3H]naloxone binding sites, would also bind irreversibly to opioid kappa receptor subtypes. We also tested the novel irreversible mu receptor antagonist, clocinnamox (14 beta-(p-chlorocinnamoylamino)-7,8-dihydro-N-cyclopropylmethylno rmorphinone mesylate). Wash-resistant inhibition (WRI) assays were conducted to detect apparent irreversible inhibition. The proportion of WRI attributable to inhibition of receptor binding, termed receptor inhibition (RI), was calculated by the equation: RI = WRI (wash-resistant inhibition) - SI (supernatant inhibition or inhibition attributable to residual drug.) Dihydrocodeinone-hydrazone, dihydrocodeinone-oxime and naloxone-3-OMe-oxime failed to produce any wash-resistant inhibition of kappa receptor binding. In contrast, preincubating guinea pig membranes with 1 microM clocinnamox produced a substantial degree of wash-resistant inhibition (greater than 90%) at kappa1 and kappa2 binding sites. However, as indicated by supernatant inhibition values of 70% to 90%, there was a large amount of residual clocinnamox which remained despite the use of an extensive washing procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of spatial orientation of the C-6-OH group in ring C of morphine derivatives on opioid activity.

The effect of epimerization on agonist and antagonist activities of morphine and dihydromorphine, and those of their N-allyl, -propyl and -cyclopropylmethyl derivatives, were studied in rat tail flick, hot plate and mice hot plate and in isolated guinea-pig ileum assays, respectively. Using the rat tail flick, hot plate and mice hot plate tests, isomorphine and dihydroisomorphine were observed to produce dose-dependent, naloxone-reversible agonist (antinociceptive) actions, in a similar dose range as their parent molecules (relative potencies: 0.6-1.9). Also, these compounds produced agonist activities in isolated tissue preparations in a naloxone-reversible manner. While the N-substituted derivatives of isomorphine and dihydroisomorphine failed to produce antinociceptive activities in the rat tail flick test, they proved to be strong agonists in the guinea-pig ileum experiments, although the Ke values of naloxone were 5-6 times higher against these compounds than against their N-CH3 counterparts. Both the agonist and antagonist activities of the N-cyclopropylmethyl derivatives were found to be most potent in the guinea-pig ileum. The epimerization of morphine and dihydromorphine and their N-substituted derivatives evoked only slight changes in opioid activities in vitro. In vivo, merely the allyl substitution on nitrogen influenced the antagonist activities of epimer pairs. In contrast, substantial changes in opioid profile were observed when N-methyl was replaced by allyl-, propyl- or cyclopropylmethyl. Changes performed this way evoked, on the one hand, an enhancement of the affinities of compounds to mu-receptors, with simultaneous loss of intrinsic efficacy at these receptors, and, on the other hand, promoted the appearance of an agonist profile on a distinct (kappa) opioid receptor.

[Synthesis and analytical characterization of dansyl derivatives of morphine-like substances]. / Morfin alkaloidok danzil-származékainak elöállítása és analitikai jellemzése.

Dansyl derivatives of morphine-like substances were prepared using dansyl-chloride in acetone in the presence of sodium hydrogen carbonate. The reaction was selective for the phenolic hydroxyl group and was also quantitative. The purity of crystalline dansyl derivatives was checked by thin layer chromatography. Their structure was confirmed by PMR and MS spectra. Characteristic chemical shifts and MS fragments of the new derivatives were determined. UV spectra of the parent compounds and the dansyl derivatives were recorded. It was found that the absorbance of dansyl derivatives at 286 nm increased four-fold and a new band appeared at 320 nm. Some thin-layer chromatographic systems were elaborated to detect and separate dansyl derivatives. HPLC studies were done using normal as well as reversed phase. Parent compounds and their dansyl derivatives were separated easily by HPLC.

[Structure-activity relationship of synthetic and semisynthetic opioid agonists and antagonists]. / Hatás-szerkezet összefüggések a szintetikus és félszintetikus opioid agonisták és antagonisták körében.

This account presents the chemical structure-pharmacological activity relationships of semi-synthetic morphine and synthetic morphinan and benzomorphan derivatives. Substitution of nitrogen confers the analgesic or morphine antagonist activity. Opiate receptor selectivity of these compounds is also discussed. The importance of morphine agonists, and antagonists is mentioned with particular reference to the opiate receptor mapping.

Synthesis and analgetic activity of nicotinic esters of morphine derivatives.

The synthesis of morphine nicotinates is described using nicotinyl chloride in the presence of pyridine. Isomorphine and isocodeine nicotinates were prepared from the corresponding morphine and codeine derivatives with nicotinic acid in the presence of triphenylphosphine and diethyl azodicarboxylate. Unexpectedly the reaction of 14-hydroxy-dihydromorphinone derivatives was anomalous, enolesters were formed. The analgetic activity of selected compounds was determined.