Micronization of Thebaine Extracted from Papaver bracteatum Lindl. Using Supercritical Fluid Technology.

BACKGROUND: Thebaine, as a main opiate alkaloid extracted from Papaveraceae plants, is widely used in the synthesis of many pharmaceutical ingredients such as buprenorphine, naltrexone, naloxone, and hydrocodone. Nevertheless, thebaine and related derivatives are often insoluble in aqueous media and have low bioavailability in digestive systems. OBJECTIVE: Reducing particle size and changing the morphology can mitigate the mentioned problem. In this study, extraction of thebaine from the capsule, stem, and root of Papaver bracteatum L. was optimized and micronization of extract components was developed to study solubility. METHODS: The extraction process was performed using supercritical carbon dioxide. Experimental central composite design was employed to determine the optimal conditions. Analysis of extract was done using a validated high performance liquid chromatography method and mass spectrometry. The micronization process was performed using an inhouse developed supercritical technique. The nanoparticles were characterized using field emission scanning electron microscopy (FESEM) and ImageJ software. The effect of micronization was explored on the solubility of extract components via ultraviolet spectroscopy. RESULTS: The percentage of thebaine in dried capsule, stem, and root powder was about 1.05, 0.31, and 0.83% respectively. The extraction results indicate that supercritical pressure has the greatest effect on the extraction yield. Analysis of FESEM images revealed that nanoparticles of extract components with particle size distribution of 5-100 nm were collected successfully. CONCLUSION: The extraction results indicate that pressure has the greatest effect on the extraction yield. In vitro studies illustrated that the solubility of extract components increased up to 1.7 times during the micronization process. HIGHLIGHTS: Expansion of supercritical methods as an effective method was performed for extracting and preparing alkaloid nanoparticles. This process led to improved oral bioavailability of alkaloids.

Altered gene expression and root thebaine production in polyploidized and methyl jasmonate-elicited Papaver bracteatum Lindl.

Persian poppy (Papaver bracteatum Lindl.) is a perennial medicinal plant belonging to the Papaveraceae family that is endemic to the mountainous areas in Northern Iran. It is known for high amounts of the valuable benzylisoquinoline alkaloid thebaine. The effects of induced polyploidy as well as the effect of methyl Jasmonate (MeJA) elicitation on the root production of thebaine and on the expression of five alkaloid biosynthesis related genes were studied. The in vitro tetraploidy induction caused a significant increased expression of norcoclaurine synthase (NCS) and salutaridinol (SAT), and a significant decreased expression of berberine bridge enzyme (BBE) in the leaves. In the root tissues, the BBE, NCS, and SAT showed an increased expression in tetraploid plants, while codeinone reductase (COR) showed a decreased expression. A similar alteration pattern was found in mixoploid plants when compared to their diploid counterparts. MeJA at concentrations of 0.1 and 0.5 mM caused a remarkable increase in the thebaine content in the roots of treated plants, where the highest thebaine content was identified in plants elicited with 0.5 mM MeJA. Elicitation treatment caused a substantial increase in the expression of NCS and SAT in the leaves, while it had no major effect on BBE, codeine 3-O-demethylase (CODM) and COR. Expression analysis in the roots showed that MeJA caused a significant increase in the expression of only BBE and NCS, while expression of other studied genes remained unchanged. Our results may be exploited for improved thebaine production and the processing of Persian poppy.

Methyl-orvinol-Dual activity opioid receptor ligand inhibits gastrointestinal transit and alleviates abdominal pain in the mouse models mimicking diarrhea-predominant irritable bowel syndrome.

BACKGROUND: Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional disorder of the gastrointestinal (GI) tract. The major IBS-D symptoms include diarrhea, abdominal pain and discomfort. High density of opioid receptors (ORs) in the GI tract and their participation in the maintenance of GI homeostasis make ORs ligands an attractive option for developing new anti-IBS-D treatments. The aim of this study was to characterize the effect of methyl-orvinol on the GI motility and secretion and in mouse models mimicking symptoms of IBS-D. METHODS: In vitro, the effects of methyl-orvinol on electrical field stimulated smooth muscle contractility and epithelial ion transport were characterized in the mouse colon. In vivo, the following tests were used to determine methyl-orvinol effect on mouse GI motility: colonic bead expulsion, whole GI transit and fecal pellet output. An antinociceptive action of methyl-orvinol was assessed in the mouse model of visceral pain induced by mustard oil. RESULTS: Methyl-orvinol (10-10 to 10-6M) inhibited colonic smooth muscle contractions in a concentration-dependent manner. This effect was reversed by naloxone (non-selective opioid antagonist) and ß-funaltrexamine (selective MOP antagonist). Experiments with a selective KOP receptor agonist, U50488 revealed that methyl-orvinol is a KOP receptor antagonist in the GI tract. Methyl-orvinol enhanced epithelial ion transport. In vivo, methyl-orvinol inhibited colonic bead expulsion and prolonged GI transit. Methyl-orvinol improved hypermotility and reduced abdominal pain in the mouse models mimicking IBS-D symptoms. CONCLUSION: Methyl-orvinol could become a promising drug candidate in chronic therapy of functional GI diseases such as IBS-D.

Possible mechanism for inhibition of morphine formation from 6-acetylmorphine after intake of street heroin.

Heroin is de-acetylated in the body to morphine in two steps. The intermediate 6-acetylmorphine (6-AM) is formed rapidly and is considered important for the pharmacological effect of heroin. In urine drug testing, an atypical pattern of morphine and 6-AM is known to occur in low frequency. The aim of this study was to investigate this atypical pattern in more detail and to identify responsible substances for a possible inhibition of the conversion from 6-AM to morphine. Urine samples were selected from a routine flow of samples sent for drug testing. Out of 695 samples containing morphine and 6-acetylmorphine, 11.5% had the atypical pattern of a 6-AM to morphine ratio above 0.26 as derived from a bimodal frequency distribution. An in vitro study of the conversion of 6-acetylmorphine to morphine in human liver homogenates demonstrated that a number of known carboxylesterase inhibitors were able to inhibit the reaction mimicking the situation in vivo. Compound 3 (3,6-Dimethoxy-4-acetoxy-5-[2-(N-methylacetamido)ethyl]phenanthrene) a substance formed from thebaine during the production of heroin was found to be a strong inhibitor. Liquid chromatography-mass spectrometry was used to identify possible inhibitors present in vivo. This part of the investigation demonstrated that several components may contribute to the effect. It is concluded that inhibition of liver carboxylesterase activity is a possible mechanism causing the atypical pattern and that one candidate compound is the result of the heroin production process. An inhibition of 6-AM metabolism is likely to increase the pharmacological effect of heroin and may be related to a higher risk of lethal toxicity.

Synthesis and pharmacological evaluation of some novel thebaine derivatives: N-(tetrazol-1H-5-yl)-6,14-endoethenotetrahydrothebaine incorporating the 1,3,4-oxadiazole or the 1,3,4-thiadiazole moiety.

In this study, we synthesized some novel N-(tetrazol-1H-5-yl)-6,14-endoethenotetrahydrothebaine 7α-substituted 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives as potential analgesic agents. The structures of the compounds were established on the basis of their IR, ¹H NMR, ¹³C NMR, 2D NMR, and high-resolution mass spectral data. The analgesic activity was evaluated by a rat-hot plate test model and a rat tail-flick model. Compound 12 showed analgesic activity higher than that of morphine. In addition to a histopathological and biochemical evaluation, the LD50 dose for the most active compound 12 was determined.

Synthesis, modeling, and pharmacological evaluation of UMB 425, a mixed µ agonist/δ antagonist opioid analgesic with reduced tolerance liabilities.

Opioid narcotics are used for the treatment of moderate-to-severe pain and primarily exert their analgesic effects through µ receptors. Although traditional µ agonists can cause undesired side effects, including tolerance, addition of δ antagonists can attenuate said side effects. Herein, we report 4a,9-dihydroxy-7a-(hydroxymethyl)-3-methyl-2,3,4,4a,5,6-hexahydro-1H-4,12-methanobenzofuro[3,2-e]isoquinolin-7(7aH)-one (UMB 425) a 5,14-bridged morphinan-based orvinol precursor synthesized from thebaine. Although UMB 425 lacks δ-specific motifs, conformationally sampled pharmacophore models for µ and δ receptors predict it to have efficacy similar to morphine at µ receptors and similar to naltrexone at δ receptors, due to the compound sampling conformations in which the hydroxyl moiety interacts with the receptors similar to orvinols. As predicted, UMB 425 exhibits a mixed µ agonist/δ antagonist profile as determined in receptor binding and [(35)S]GTPγS functional assays in CHO cells. In vivo studies in mice show that UMB 425 displays potent antinociception in the hot plate and tail-flick assays. The antinociceptive effects of UMB 425 are blocked by naloxone, but not by the κ-selective antagonist norbinaltorphimine. During a 6-day tolerance paradigm, UMB 425 maintains significantly greater antinociception compared to morphine. These studies thus indicate that, even in the absence of δ-specific motifs fused to the C-ring, UMB 425 has mixed µ agonist/δ antagonist properties in vitro that translate to reduced tolerance liabilities in vivo.

Pharmacological mechanisms underlying the antinociceptive and tolerance effects of the 6,14-bridged oripavine compound 030418.

AIM: To investigate possible pharmacological mechanisms underlying the antinociceptive effect of and tolerance to N-methyl-7α-[(R)-1-hydroxy-1-methyl-3-(thien-3-yl)-propyl]-6,14-endo-ethanotetrahydronororipavine (030418), a derivative of thienorphine. METHODS: The binding affinity and efficacy of 030418 were determined using receptor binding and guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPγS) assays in CHO-µ, CHO-κ, CHO-δ, and CHO-ORL1 cell membranes. The analgesic activity of and tolerance to 030418 were evaluated in thermal nociceptive tests in mice. The effects of 030418 on opioid receptors were further investigated using in vivo pharmacological antagonist blockade and in vitro tissue preparations. RESULTS: The compound 030418 displayed high binding affinity to all subtypes of opioid receptors with K(i) values in the nanomolar range. In [(35)S]GTPγS binding assay, the maximal stimulation of 030418 to µ-, κ-, δ-receptors and the ORL1 receptor was 89%, 86%, 67% and 91%, respectively. In hot-plate test, the antinociceptive effect of 030418 was more potent and longer than morphine. The nonselective opioid receptor antagonist naloxone could completely block 030418-induced antinociception, while both the µ-opioid receptor antagonist ß-FNA and the κ-opioid receptor antagonist nor-BNI attenuated 030418-induced antinociception. In contrast, the ORL1 receptor antagonist J-113397 enhanced the antinociceptive effect of 030418. Additionally, chronic treatment with 030418 resulted in a dramatic development of tolerance that could not be effectively prevented by J-113397. In guinea pig ileum preparation, the existing action of 030418 could be removed with difficulty after prolonged washing. CONCLUSION: The compound 030418 is a novel agonist of opioid receptors with high efficiency, long-lasting effect and liability to tolerance, which may be closely correlated with the methyl group at the N(17) position and the high hydrophobicity of the C(7)-thiophene group in its chemical structure.

Recent developments in the chemistry of thebaine and its transformation products as pharmacological targets.

The most practical synthetic routes to the preparation of as important pharmaceuticals as oxycodone, naloxone, naltrexone, nalbuphine and buprenorphine have utilized the alkaloid, thebaine, as a starting material. This review intends to focus on chemical transformations of morphinans which resulted in morphinandiene derivatives with well-established and novel pharmacological potencies. These chemical transformations were mainly associated with the formation and substitution of the unique diene structure of the ring C of the morphinan backbone.

Cinnamoyl derivatives of 7alpha-aminomethyl-6,14-endo-ethanotetrahydrothebaine and 7alpha-aminomethyl-6,14-endo-ethanotetrahydrooripavine and related opioid ligands.

A new series of ligands has been synthesized where the cinnamoyl group of the 14-cinnamoylamino morphinones has been introduced to the 7alpha-substituent of the 6,14-bridged oripavine series. In vitro the compounds were mostly low efficacy partial agonists or antagonists with some selectivity for the mu opioid receptor, with evidence of micro efficacy in vivo. The similarity in SAR between these 6,14-bridged oripavines and the 14-cinnamoylamino series suggests a similar mode of interaction with the micro opioid receptor.

The orvinols and related opioids--high affinity ligands with diverse efficacy profiles.

The thevinols and orvinols derived from thebaine via the thebaine-methylvinyl ketone adduct (thevinone) were thoroughly investigated in the 1960's and 1970's by the Reckitt group. From this work a number of important opioids emerged. Buprenorphine is a mu partial agonist, kappa/delta-antagonist that is now used primarily in the treatment of heroin abuse and dependence though it was initially launched as an analgesic for the treatment of moderate to severe pain. Etorphine and dihydroetorphine are very potent mu agonists that have found application in veterinary and human medicine respectively. Diprenorphine is primarily a mu antagonist though it also has some kappa-partial agonist effects. It has high affinity for all types of opioid receptors and as a "universal" opioid ligand has been much in demand as a pharmacological tool. It has also been converted into a [11C] version for use in Positron Emission Tomography (PET) studies of brain function related to the opioid receptor system. More recent medicinal chemistry investigations have been concerned with gaining a greater understanding of buprenorphine's unique opioid profile. This has involved the synthesis and evaluation of a number of series of buprenorphine analogues in which the C20 t-butyl group has been constrained in a ring system. These studies have suggested that the methyls in the t-butyl group inhibit the conformational changes in the kappa-receptor required for generation of an agonist response. Introduction of a 7alpha-cinnamoylaminomethyl group in place of the orvinol tertiary alcohol function leads to selective irreversible mu antagonism.

Differential binding properties of oripavines at cloned mu- and delta-opioid receptors.

This study examines the possibility that oripavine opioid receptor agonists bind equally to both high and low affinity states of the mu-opioid receptor. Studies were performed in C6 cells expressing mu- or delta-opioid receptors; high and low agonist affinity states of the receptors were defined by the absence and presence, respectively of Na+ ions and the GTP analog Gpp(NH)p. At the mu-opioid receptor dihydroetorphine and etorphine were full agonists, buprenorphine had moderate efficacy while diprenorphine was an antagonist. At the delta-opioid receptor, dihydroetorphine, etorphine, and diprenorphine had moderate efficacy while buprenorphine was an antagonist. The binding affinities of the oripavines at the mu-opioid receptor decreased only one to 2-fold in the presence of NaCl and Gpp(NH)p. In contrast, decreases in oripavine affinity at the delta-opioid receptor correlated with delta-opioid receptor efficacy. The ability of oripavine agonists to bind with high affinity to the low agonist affinity state of the nu-opioid receptor may explain the high potencies of these compounds in vivo.

Synthesis and pharmacological activity of thebaine-derived mu-opioid receptor agonists.

Thebaine-derived mu-opioid agonists were synthesized through the reaction of thebaine with N-aryl maleimide and tested for opioid activity. Morphine was used as reference compound. Our results show that an attachment of aryl succinimide group to thebaine produced series of compounds with mu-opioid agonist activity. The most active compound in smooth muscle preparation was compound 6 with an IC50 ratio of delta/mu = 248.69 and was as potent as morphine with ED50 value 26.65 mg kg-1 i.p. in hot-plate test and showed good antinociceptive activity.

Stereoselective mu- and delta-opioid receptor-related antinociception and binding with (+)-thebaine.

In vivo and in vitro binding studies with natural thebaine and its enantiomer, (+)-thebaine were conducted to elucidate further their interactions with the opioid system. (-)-Thebaine a key intermediate in the biosynthesis of morphine in the poppy plant (Papaver somniferum) and in mammalian tissue, was poorly effective antinociceptively in mice at doses to 30 mg/kg. Its principal behavioral manifestation was lethal convulsions. Naltrindole, at doses of 1 and 10 mg/kg did not block either the convulsions or lethal effects, suggesting that the delta-opioid receptor system was not involved in this action. Surprisingly, the dextrorotatory isomer exhibited significant antinociceptive activity in the tail-flick [ED50 = 8.9 (3.4-22.1) mg/kg], hot-plate [ED50 = 22.9 (10.9-48.1) mg/kg] and phenylquinone [ED50) = 1.9 (1.6-9.5) mg/kg] assays. Studies with opioid receptor-subtype antagonists, beta-funaltrexamine, nor-binaltorphimine and naltrindole, indicated that antinociception was associated with mu- and delta-opioid receptors. Results of displacement experiments supported the in vivo data. Significant competition for [3H]diprenorphine binding with both isomers for cloned mu- and delta-opioid receptors was observed. However, (-)-thebaine was more effective at the delta-opioid receptor (Ki = 1.02+/-0.01 microM) whereas (+)-thebaine was more effective at the mu-opioid receptor ( Ki = 2.75+/-0.01 microM). Opioid-induced antinociception associated with unnatural thebaine raises the possibility of additional mu- and delta-opioid receptor sites.

[Pharmacological study on an irreversible ligand of opioid receptors, A-alpha-CAM, and its reaction with the sulfhydryl group].

A-alpha-CAM is an irreversible partial agonist of opiate receptors. Its binding to opioid receptors from P2 membrane preparations of rat brain and its effect on isolated tissues (GPI, MVD, RVD and RbVD) could not be washed away, indicating the irreversible nature of its binding. A-alpha-CAM inhibited the electrically elicited contraction of GPI, a pure agonist, with an IC50 of 2.6 mumol/L, and this effect could not be antagonized by Nx. A-alpha-CAM acted as a partial agonist on MVD with an IC50 of 0.153 mumol/L. With RVD and RbVD, A-alpha-CAM acted as an antagonist with PA2 values of 7.4 and 7.7 respectively. Possibly, covalent binding of A-alpha-CAM with the sulfhydryl groups of opioid receptors is the biochemical mechanisms responsible for its irreversible action.

[Molecular basis of pharmacological action of irreversible opioid receptor agonist alpha-CAO].

Molecular mechanism of opioid effect was studied in mouse brain using alpha-CAO (7 alpha-N, N-Bis (beta-chloroethyl)amino-6, 14-endo-ethenotetrahydrooripavine), an irreversible opioid receptor agonist. There was a biphasic response in cerebral cAMP content, including an initial sharp decline and a subsequent increase 3 days later, the response being in line with analgesic effect initiated by administration of alpha-CAO and development of habituation due to sustained drug administration. Further laboratory study indicated that in the acute stage, adenylate cyclase activity in the mouse brain was inhibited by 48% and the inhibitory effect was reversible by naloxone. The delayed effect of alpha-CAO in development of habituation was accompanied by increase of AC activity and cAMP content of the brain, calmodulin content in the brain. The later being also causative factor in development of habituation.

[Irreversible action of the opioid agonist alpha-CAM and its reaction with SH groups at opioid receptor binding sites].

7 alpha-Bis (beta-chloroethyl)amino-methyl-6,14-endoethenotetrahydrooripavine (alpha-CAM) was found to bind to opioid receptors irreversibly and react directly with sulfhydryl (SH) groups in P2 preparations of rat brain. The P2 preparations were pretreated as follows: protection of the SH groups at the opioid receptor binding sites by morphine or etorphine, and inactivation of the SH groups outside the binding sites by N-ethylmaleimide (NEM), followed by removal of the morphine or etorphine by washing. alpha-CAM was still able to bind the pretreated P2 preparations in an irreversible manner. The results indicate that the formation of covalent bonds between alpha-CAM and the SH groups of opioid receptor binding sites is possibly one of the biochemical mechanisms of the irreversible action of alpha-CAM.

Pharmacological study of an irreversible partial agonist of opiate receptors, A-alpha-CAO.

A-alpha-CAO induces weak analgesia with very short duration in mice and is able to antagonize the analgesic effect of morphine (Mor) up to 3-4 days after a single injection. No tendency of dependence has been observed. It acts as a partial agonist on MVD with Ke value of 9 X 10(-9) mol/L. Its antagonist effect remains after several washes and its agonist effect cannot be reversed by naloxone (Nx), provided the incubation time or the concentration of the agent is sufficient. On isolated GPI, A-alpha-CAO is a pure agonist with IC50 of 5.7 X 10(-10) mol/L; this agonist effect cannot be removed by washing but can be reversed by Nx. On RVD and RbVD, it has antagonist effect against beta-endorphine (beta-end) and U50488H, which cannot be washed out easily, and the pA2 are 7.5 and 7.6 respectively. A-alpha-CAO also inhibits the specific binding of 3H-etorphine (3H-Etor) to the P2 fraction of the mouse brain membrane with an IC50 of 3.2 X 10(-9) mol/L. The inhibition on the high affinity binding sites of 3H-Etor remains 95% even after 6 washes.

[Pharmacological study on a new irreversible agonist of opioid receptors, 7 alpha-bis(beta-chloroethyl) aminomethyl-6, 14-endoetheno-tetrahydrooripavine].

7 alpha-bis (beta-chloroethyl) aminomethyl-6, 14-endoetheno-tetrahydro oripavine (alpha-CAM) is a new irreversible opioid receptor agonist. Its effect on isolated tissues (guinea pig ileum, mouse vas deferens, rat vas deferens and rabbit vas deferens) were studied. It was shown to be bound irreversibly to rat brain P2 membrane preparations. The ED50 of its analgesic effect in mice (icv) was found to be 0.12 nmol/mouse, and the effect may last as long as 2-3 days. It is a compound which produces the longest analgesia known up to date. A single dose (icv) of alpha-CAM was sufficient to produce dependence in mice. Thus, the compound may serve as an agent for studying the mechanism of physical dependence.