Boldine suppresses dextran sulfate sodium-induced mouse experimental colitis: NF-κB and IL-6/STAT3 as potential targets

Ulcerative colitis (UC) is a nonspecific inflammatory disorder characterized by oxidative and nitrosative stress, leucocyte infiltration, and upregulation of inflammatory mediators. Boldine is an alkaloid compound found in Boldo tree, with multiple pharmacological actions, mainly anti-inflammatory, antioxidant, antitumor, and immunomodulatory activities. Hence, the effect of boldine for its anti-inflammatory properties against dextran sulfate sodium (DSS)-induced UC in BALB/c mice was studied. Administration of boldine to DSS-induced mice protects colon damage by reduced disease activity index, spleen weight, and increased colon length. Also administration of boldine showed a reduction in the activity of myeloperoxidase (MPO) and CD 68+ expression. Boldine reduced the colon damage, with significant reductions in both the extent and the severity of the inflammation as well as in crypt damage and leukocyte infiltration in the mucosa. Analysis in vivo showed clear decrease in the production of tumor necrosis factor (TNF)-α, Interleukin (IL)-6, IL-17, and signal transducer and activator of transcription-(p-STAT3)(Y705) with nuclear factor (p65-NF-κB) production being reduced significantly. Moreover, p65-NF-κB activation was reduced in mouse macrophage RAW 264.7 cells in vitro. The data demonstrated that boldine may be beneficial in colitis through selective immunomodulatory effects, which may be mediated, at least in part, by inhibition of p65-NF-κB and STAT3 signaling pathways. © 2016 BioFactors, 42(3):247-258, 2016.

[Analysis of some species of magnolia introduced to west georgia, on content of aporphine alkaloids and their biological activity]

The goal of research was study of vegetative organs of Magnolia species introduced to west Georgia on qualitative and quantitative content of aporphine alkaloids and evaluate cytotoxic activity of total alkaloids from M. officinalis and M. glauca against A-549, DLD-1 and WS-1. Qualitative and quantitative content of aporphine alkaloids in different vegetative organs were determined by chromatographic methods. Based on the researches alkaloids - liriodenine and lanuginozine are characteristic for leaves, for bark of branches - liriodenine, d-caaverine; for bark of trunk - a liriodenine, a caaverine and a magnoflorine. Liriodenine may be considered as is chemotaxonomic sign of genus Magnolia, as it was found in all analyzed vegetative organs. In vitro cytotoxic activity of total alkaloids of M. officinalis and M. glauca has been investigated against DLD-1, WS-1 and A-549. Total alkaloids of M. glauca expressed significant cytotoxic activity against DLD-1 and WS-1, and medium cytotoxicity against A-549; M. officinalis exerted middle activity against A-549, DLD-1, WS-1.

Isocorydine derivatives and their anticancer activities

In order to improve the anticancer activity of isocorydine (ICD), ten isocorydine derivatives were prepared through chemical structure modifications, and their in vitro and in vivo activities were experimentally investigated. 8-Amino-isocorydine (8) and 6a,7-dihydrogen-isocorydione (10) could inhibit the growth of human lung (A549), gastric (SGC7901) and liver (HepG2) cancer cell lines in vitro. Isocorydione (2) could inhibit the tumor growth of murine sarcoma S180-bearing mice, and 8-acetamino-isocorydine (11), a pro-drug of 8-amino-isocorydine (8), which is instable in water solution at room temperature, had a good inhibitory effect on murine hepatoma H22-induced tumors. The results suggested that the isocorydine structural modifications at C-8 could significantly improve the biological activity of this alkaloid, indicating its suitability as a lead compound in the development of an effective anticancer agent.

Aporphine alkaloids from the leaves of Phoebe grandis (Nees) Mer. (Lauraceae) and their cytotoxic and antibacterial activities

The oxoaporphine alkaloid lysicamine (1), and three proaporphine alkaloids, litsericinone (2), 8,9,11,12-tetrahydromecambrine (3) and hexahydromecambrine A (4) were isolated from the leaves of Phoebe grandis (Nees) Merr. (Lauraceae). Compounds 2 and 3 were first time isolated as new naturally occurring compounds from plants. The NMR data for the compounds 2-4 have never been reported so far. Compounds 1 and 2 showed significant cytotoxic activity against a MCF7 (human estrogen receptor (ER+) positive breast cancer) cell line with IC₅₀ values of 26 and 60 µg/mL, respectively. Furthermore, in vitro cytotoxic activity against HepG2 (human liver cancer) cell line was evaluated for compounds 1-4 with IC₅₀ values of 27, 14, 81 and 20 µg/mL, respectively. Lysicamine (1) displayed strong antibacterial activity against Bacillus subtilis (B145), Staphylococcus aureus (S1434) and Staphylococus epidermidis (a clinically isolated strain) with inhibition zones of 15.50 ± 0.57, 13.33 ± 0.57 and 12.00 ± 0.00 mm, respectively. However, none of the tested pathogenic bacteria were susceptible towards compounds 2 and 3.

Acetylcholinesterase and butyrylcholinesterase inhibitory compounds from Corydalis cava Schweigg. & Kort

In the course of screening plants used in Danish folk medicine as memory enhancers, a crude methanolic extract of tubers from Corydalis cava showed significant acetylcholinesterase inhibitory activity in a dose-dependent manner. Activity guided fractionation of the methanolic extract resulted in the isolation of three alkaloids, bulbocapnine (1), corydaline (2) and corydine (3) as active constituents. Bulbocapnine inhibited acetylcholinesterase as well as butyrylcholinesterase in a dose-dependent manner with IC(50) values of 40+/-2 microM and 83+/-3 microM, respectively. Corydaline inhibited acetylcholinesterase in a dose-dependent manner with an IC(50) value of 15+/-3 microM and corydine inhibited butyrylcholinesterase in a dose-dependent manner with an IC(50) value of 52+/-4 microM. Corydaline was considered inactive against butyrylcholinesterase and corydine against acetylcholinesterase, due to IC(50)>100 microM.

[Study on pharmacokinetics of crebanine injection in rabbits]

OBJECTIVE

To develop an HPLC method for the determination of serum level of Crebanine (Cre) and study on the pharmacokinetics of Cre injection in rabbits.

METHOD

To sample blood serum from the rabbits' ears which were injected the Cre by 2.0 mg x kg(-1) at different time and use HPLC to determine the concentration of Cre in it, the pharmacokinetic parameters were accessed by the DAS software.

RESULT

Cre was fitted to a two compartment open pharmacokinetic model in rabbits. There was no signifiant difference between the male and female rabbits'pharmacokinetic by t-test. The mainly pharmacokinetic parameters were: t1/2alpha = (3. 246 +/-0.222) min, t1/2beta = (36.67+/-5.52) min, Cmax = (1.401 +/- 0.062) mg x L(-1), Vd = (5.928 +/- 0.877) L x kg(-1), Cl = (0. 051 +/-0.003) L x min(-1) x kg(-1).

CONCLUSION

This experiment can objectively show the pharmacokinetics regularity of Crebanine injection in rabbits. Crebanine injection was a speeding disposition drug (t1/2 <1 h) and disposed extensively and rapidly in rabbits.

Anthelmintic activity of aporphine alkaloids from Cissampelos capensis

Two known aporphine alkaloids, (S)-dicentrine (1) and (S)-neolitsine (2), have been isolated from the MeOH extract of the aerial parts of Cissampelos capensis (Menispermaceae). The structures of these compounds were elucidated by NMR and MS analysis and comparison to literature data. These compounds were isolated by bioassay-guided fractionation using the Haemonchus contortus larval development assay. Compounds 1 and 2 exhibited EC90 values (concentration at which 90% loss of larval motility is observed) of 6.3 and 6.4 microg/mL, respectively. In an IN VIVO assay, administration of 1 resulted in 67% reduction of worm counts in mice at 25 mg/kg when dosed orally.

8-NH2-boldine, an antagonist of alpha1A and alpha1B adrenoceptors without affinity for the alpha1D subtype: structural requirements for aporphines at alpha1-adrenoceptor subtypes

Structure-activity analysis of 21 aporphine derivatives was performed by examining their affinities for cloned human alpha (1A), alpha (1B) and alpha (1D) adrenoceptors (AR) using membranes prepared from rat-1 fibroblasts stably expressing each alpha (1)-AR subtype. All the compounds tested competed for [ (125)I]-HEAT binding with steep and monophasic curves. The most interesting compound was 8-NH (2)-boldine, which retains the selective affinity for alpha(1A)-AR (pKi = 6.37 +/- 0.21) vs. alpha(1B)-AR (pKi = 5.53 +/- 0.11) exhibited by 1,2,9,10-tetraoxygenated aporphines, but shows low affinity for alpha(1D)-AR (pKi < 2.5). Binding studies on native adrenoceptors present in rat cerebral cortex confirms the results obtained for human cloned alpha (1)-AR subtypes. The compounds selective for the alpha (1A) subtype discriminate two binding sites in rat cerebral cortex confirming a mixed population of alpha (1A)- and alpha (1B)-AR in this tissue. All compounds are more selective as inhibitors of [ (3)H]-prazosin binding than of [ (3)H]-diltiazem binding to rat cerebral cortical membranes. A close relationship was found between affinities obtained for cloned alpha (1A)-AR and inhibitory potencies on noradrenaline-induced contraction or inositol phosphate accumulation in tail artery, confirming that there is a homogeneous functional population of alpha(1A)-AR in this vessel. On the contrary, a poor correlation seems to exist between the affinity of 8-NH (2)-boldine for cloned alpha (1D)-AR and its potency as an inhibitor of noradrenaline-induced contraction or inositol phosphate accumulation in rat aorta, which confirms that a heterogeneous population of alpha (1)-AR mediates the adrenergic response in this vessel.

Ocular pharmacology of bicyclic hexahydroaporphines

This paper explores the ocular hypotensive actions of bicyclic analogs of hexahydroaporphine (HHA), specifically nor-HHA, in an attempt to shed light on the mechanism(s) by which they lower intraocular pressure (IOP). Studies involving the measurement of IOP and aqueous humor production were conducted in ocular normotensive albino rabbits, while those involving smooth muscle contractility utilized isolated bovine iris. The ability of nor-HHA to produce a sustained drop in IOP is linked to both a functioning adrenergic nervous system and the availability of the products of cyclooxygenase metabolism. Although aqueous flow is not impacted by the bicyclic structures, the significant enhancement of outflow facility points to a probable mechanism of IOP-lowering action. Nor-HHA had no direct contractile or relaxant action on bovine irides, but does cause a concentration-dependent inhibition of carbachol-evoked contractions. This inhibition was reversed by inhibitors of phospholipase A(2) and cyclooxygenase, but not by inhibitors of lipoxygenase, again indicating a role for prostaglandins in the ocular pharmacological action of bicyclic HHAs. Pretreatment with a nitric oxide (NO) scavenger also reversed the ability of nor-HHA to inhibit carbachol-induced contractions, implying a role for NO in the postjunctional actions of HHAs.

Vascular activity of (-)-anonaine, (-)-roemerine and (-)-pukateine, three natural 6a(R)-1,2-methylenedioxyaporphines with different affinities for alpha1-adrenoceptor subtypes

We have studied the mechanism of action of three 6a( R)-1,2-methylenedioxyaporphines as vasorelaxant compounds. The alkaloids assayed showed different affinities for the three human cloned alpha (1)-adrenoceptor (AR) subtypes stably expressed in rat-1 fibroblasts, showing lower affinity for alpha(1B)-AR with regard to the alpha(1A)- or alpha(1D)-subtypes. These three natural compounds are more potent inhibitors of [ (3)H]-prazosin binding than of [ (3)H]-diltiazem binding to rat cerebral cortical membranes. As all these alkaloids inhibited noradrenaline (NA)-induced [ (3)H]-inositol phosphate formation in cerebral cortex and rat tail artery, they may be safely viewed as alpha (1)-AR antagonists, as is demonstrated by the vasorelaxant responses observed in isolated rat tail artery and/or aorta precontracted with NA. The alkaloids also inhibited the contractile response evoked by KCl (80 mM) but with a lower potency than that shown against NA-induced contraction. We have also examined their ability to inhibit the different forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aortic smooth muscle and endothelial cells, with negative results. We conclude that N-methylation favours the interaction of (R)-aporphines with all alpha (1)-AR subtypes, and that the topography of the binding site recognizing the basic or protonated nitrogen atom is similar in all three alpha (1)-AR subtypes. The presence of a hydroxy group at C-11 has different effects on the affinity for each alpha (1)-AR subtype but decreases the affinity for Ca (2+) channels. These results confirm and extend the view that subtle changes in the hydroxylation patterns on the aromatic ring of the aporphine structure affect the interactions of these compounds with the three alpha (1)-AR subtypes in different ways, suggesting that the binding site recognizing the aporphine skeleton is different in each of the three subtypes.

Nantenine: an antagonist of the behavioral and physiological effects of MDMA in mice

RATIONALE

No selective antagonists for the effects of MDMA have yet been identified. The structurally-similar, naturally-occurring plant alkaloid nantenine (9,10-methylenedioxy-1,2 dimethoxyaporphine) may represent such a compound.

OBJECTIVES

To investigate the capacity of nantenine to block and/or reverse MDMA-induced hyperthermia, lethality, locomotor stimulation, and head twitches in mice, and to compare these actions with those of the selective alpha1 antagonist prazosin and the selective 5-HT2A antagonist M100907.

METHODS

Pretreatments of either 10 mg/kg nantenine or 1 mg/kg prazosin were administered 15 min before 32 mg/kg MDMA; core temperature and locomotor stimulation were then monitored via radiotelemetry for at least 3 h. In further hyperthermia studies, 32 mg/kg MDMA was administered first and temperature was allowed to rise for 30 min; 10 mg/kg nantenine, 1 mg/kg prazosin, or 1 mg/kg M100907 was then administered in an attempt to reverse MDMA-induced hyperthermia. In lethality assays, percent lethality was quantified 2 h after MDMA injection in two distinct housing conditions, one or 12 mice per cage, with or without 15 min pretreatments of 10 mg/kg nantenine or 1 mg/kg prazosin. Drug elicited head twitches were quantified for 10 min following administration of either MDMA enantiomer, with and without pretreatments of 1 mg/kg nantenine, 0.1 mg/kg prazosin, or 0.001 mg/kg M100907.

RESULTS

Nantenine blocked and rapidly reversed MDMA-induced hyperthermia, attenuated lethality in both housing conditions, and reduced MDMA-induced locomotor stimulation and head twitches in mice. Prazosin blocked, but did not reverse, MDMA-induced hyperthermia, attenuated lethality (more effectively in singly-housed animals), and reduced MDMA-induced locomotor stimulation and head twitches. M100907 did not reverse MDMA-induced hyperthermia, but effectively blocked drug-elicited head twitches.

CONCLUSIONS

Nantenine functions as an effective antagonist against a wide range of MDMA-induced effects in mice. The antagonist actions of this compound at serotonin and adrenergic receptors may be differentially implicated across endpoints.

Alkaloids from Cassytha filiformis and related aporphines: antitrypanosomal activity, cytotoxicity, and interaction with DNA and topoisomerases

Cassytha filiformis (Lauraceae), a widely distributed parasitic plant, contains several aporphine alkaloids and is often used in African folk medicine to treat cancer, African trypanosomiasis and other diseases. In a previous investigation, we showed that the alkaloid plant extract and the isolated aporphines possessed in vitro cytotoxic properties. In this paper, we evaluated the in vitro activity of the alkaloid extract (IC50 = 2.2 microg/mL) and its three major aporphine alkaloids (actinodaphnine, cassythine, and dicentrine) on Trypanosoma brucei brucei as well as four related commercially available aporphines (bulbocapnine, glaucine, isocorydine, boldine). Only the three alkaloids from Cassytha filiformis were active on the trypanosomes in vitro (IC50 = 3-15 microM). Additionally, we compared the cytotoxicity of these seven compounds on HeLa cells. Glaucine was the most cytotoxic compound on HeLa cells (IC50 = 8.2 microM) in the series. In order to elucidate their mechanism of action, the binding mode of these molecules to DNA was studied by UV absorption, circular and linear dichroism spectroscopy. The results of the optical measurements indicated that all seven aporphines effectively bind to DNA and behave as typical intercalating agents. Biochemical experiments showed that actinodaphnine, cassythine and dicentrine also interfere with the catalytic activity of topoisomerases in contrast to the four other aporphines. These interactions with DNA may explain, at least in part, the effects observed on cancer cells and on trypanosomes.

Acute cardiovascular effects of (+)-nantenine, an alkaloid isolated from Platycapnos spicata, in anaesthetised normotensive rats

This is the first study of the in vivo potential activity of (+)-nantenine (a natural aporphinoid alkaloid) on the rat cardiovascular system. In anaesthetized normotensive rats, acute intravenous ( i. v.) administration of (+)-nantenine (3 - 6 mg/kg) produced a dose-dependent fall in mean arterial pressure (MAP), accompanied by a significant decrease in heart rate (HR). In addition, (+)-nantenine (5 mg/kg i. v.) did not modify the cardiovascular effects induced by angiotensin II (0.2 microg/kg i. v.) and the selective alpha (2)-adrenoceptor agonist B-HT 920 (0.2 mg/kg i. v.) [unlike nifedipine (0.8 mg/kg i. v.) and yohimbine (1 mg/kg i. v.), respectively] but markedly attenuated [like prazosin (0.2 mg/kg i. v.)] the hypertension evoked by phenylephrine (PE, 25 microg/kg, i. v.), a selective alpha (1)-adrenergic receptor agonist and, like ketanserin (1 mg/kg i. v.), the second phase (rise in MAP) of the cardiovascular response caused by 5-hydroxytryptamine (5-HT, 0.3 mg/kg i. v.). On the other hand, pre-treatment of anaesthetised rats with NG-nitro- L-arginine ( L-NOARG, 5 mg/kg i. v.) did not significantly affect the cardiovascular effects of (+)-nantenine. These results indicate that the hypotension and bradycardia elicited by this aporphine alkaloid in anaesthetised normotensive rats seem to be due, at least in part, to a combined alpha (1)-adrenergic and 5-HT (2A) receptor blockade but not to the release of nitric oxide (NO) from vascular endothelium, to an alpha (2)-adrenoceptor antagonism or to a calcium antagonist activity. Abbreviations. BP:blood pressure HR:heart rate 5-HT:5-hydroxytryptamine i. v.:intravenous L-NOARG: NG-nitro- L-arginine MAP:mean arterial pressure NO:nitric oxide PE:phenylephrine

Cytotoxic and DNA damaging activity of some aporphine alkaloids from Stephania dinklagei

Six aporphine alkaloids, liriodenine, corydine, isocorydine, atherospermidine, stephalagine and dehydrostephalagine, were isolated by bioassay-guided fractionation of the EtOH extract of the stems of Stephania dinklagei. Liriodenine showed strong cytotoxic activity while corydine and atherospermidine showed DNA damaging activity. Dehydrostephalagine and atherospermidine were isolated from this plant for the first time.

(+)-Nantenine isolated from Nandina domestica Thunb. inhibits adrenergic pressor responses in pithed rats

The effects of (+)-nantenine on various pressor responses, recently reported exerting competitive antagonistic activity at the alpha1-adrenoceptor/5-hydroxytryptamine (5-HT)2A receptor, were examined in vivo. (+)-Nantenine (0.03-3 mg/kg) caused a dose-dependent inhibition of the pressor response to phenylephrine (alpha1-adrenoceptor agonist) or 5-HT (5-HT receptor agonist) in both anesthetized and pithed rats. The pressor response to UK 14304 (5-Bromo-N-[2-imidazolin-2-yl]-6-quinoxalinamine) (an alpha2-adrenoceptor agonist) was inhibited by (+)-nantenine (0.003-3 mg/kg) in pithed rats in a dose-dependent manner without affecting the angiotensin II-induced pressor response in anesthetized rats. The pressor response to sympathetic nerve stimulation was also inhibited by (+)-nantenine (0.3-3 mg/kg) in a dose-dependent manner. (+)-Nantenine (3 mg/kg) facilitated the norepinephrine release induced by sympathetic nerve stimulation in pithed rats. In the guinea pig vas deferens, the initial component of contractions induced by electrical field stimulation was enhanced by (+)-nantenine (1-30 microM) in a concentration-dependent manner, while the later component was inhibited by it. These data suggest that (+)-nantenine has antagonistic activities on alpha1-adrenoceptors, alpha2-adrenoceptors and 5-HT2A receptors in pithed rats.

Pharmacological effects of (+)-nantenine, an alkaloid isolated from Platycapnos spicata, in several rat isolated tissues

In this work, the potential activity of (+)-nantenine (a natural aporphin alkaloid) in several rat isolated tissues was studied. In rat isolated intact aorta, (+)-nantenine (0.05 - 0.5 microM) competitively antagonized with almost equal effectiveness the contractions produced by phenylephrine (PE) and 5-hydroxytryptamine (5-HT) in normal Krebs solution. However, at higher concentrations (2 microM), the alkaloid also reduced the maximal effect induced by these two agonists. In depolarizing Ca2+-free high KCl 50 mM solution, (+)-nantenine (1.5 - 6 microM) inhibited, in a non-competitive way, the increase in tension evoked by Ca2+ with depression of the maximum response. On the other hand, (+)-nantenine (3 - 30 microM) did not affect the contractile effect caused by okadaic acid (OA, 1 microM) while, however, this alkaloid totally relaxed, in a concentration-dependent fashion, the contractions produced by phorbol 12-myristate 13-acetate (PMA, 1 microM) in endothelium-containing rat aortic rings. (+)-Nantenine (1 - 30 microM) reversed and competitively antagonized the inhibitory action induced by B-HT 920 in electrically-stimulated rat vas deferens. In isolated rat atria, (+)-nantenine (3 - 10 microM) diminished the contraction frequency. (+)-Nantenine (3 microM) significantly reduced the depolarization (voltage)-activated transient (T-type) and sustained (long-lasting, L-type) barium inward currents [ IBa(T) and IBa(L) ] recorded in whole cell-clamped rat aortic myocytes. These results indicate that the pharmacological effects of (+)-nantenine observed at concentrations lower than 1 microM can be attributed to alpha 1 -adrenergic and 5-HT 2A receptor blocking properties whereas at higher concentrations (> 1 microM) the pharmacological activity of this natural compound may be also due to a decrease of Ca2+ influx through transmembrane calcium channels (calcium antagonist activity), to an inhibition of PKC actions and/or to an alpha 2 -adrenoceptor blockade.

Nantenine alkaloid presents anticonvulsant effect on two classical animal models

The present study investigated the anticonvulsant and convulsant profiles of nantenine, an aporphine alkaloid found in several vegetal species. At lower doses (20-50 mg/kg, i.p.) the alkaloid proved to be effective in inhibiting pentylenotetrazol- (PTZ 100 mg/kg, s.c.) and maximal electroshock-induced seizures (80 mA, 50 pulses/s, 0.2 s), suggesting its potential as an anticonvulsant drug. However, at higher doses (> or = 75 mg/kg, i.p.) a convulsant activity was observed. Comparing the present in vivo nantenine effects on seizures with previous in vitro biphasic action on Na+, K+-ATPase activity, the convulsant effect appears to be related to inhibition of these phosphatase at high doses whereas anticonvulsant effect, observed at low doses, seems attributable to its stimulation and the resultant decrease of Ca2+-influx into the cell.

Potential sites of action of TNPA: a dopamine-2 receptor agonist

The purpose of this study was to correlate potential mechanisms with site(s) of action for TNPA-induced ocular hypotension. In response to R(-)-2, 10, 11-trihydroxy-N-propyl-noraporphine hydrobromide (TNPA, 75 microg), a D2 dopamine receptor agonist, the intraocular pressure decreased by 4.5 and 8 mm Hg at 1 and 2 hr, respectively, as measured by pneumatonometry. The levels of norepinephrine in aqueous humor, as determined by high performance liquid chromatography with electrochemical detection, were reduced by 38% and 79% at 1 and 2 hr, respectively, following topical application of TNPA (75 microg). Following pretreatment with raclopride (750 microg), a D2 receptor antagonist, and a subsequent challenge with TNPA (75 microg), the depression of intraocular pressure and levels of norepinephrine induced by TNPA (75 microg, 2 hr) were antagonized. In order to examine sites of action, immunohistochemistry of D2 dopamine receptors was performed in the ciliary body of normal and sympathetically denervated rabbits utilizing a goat polyclonal D2 receptor IgG and anti-goat IgG-FITC. Results from immunolocalization experiments demonstrated that D2 receptors are present on postganglionic sympathetic nerves in the ciliary body of normal rabbits but minimally detectable in that of sympathectomized rabbits. It is concluded that immunohistochemical identification of D2 receptors in the ciliary body associated with the suppression of aqueous norepinephrine levels by topical application of the D2 receptor agonist, TNPA, provide strong evidence of prejunctional (neuronal) site of action of TNPA. Antagonism of TNPA-induced ocular hypotension by raclopride coupled with the immunohistochemical and norepinephrine data suggest that D2 dopamine receptors are located on postganglionic sympathetic neurons in the ciliary body.

Pharmacological evaluation of ocoteine, isolated from Cassytha filiformis, as an alpha 1-adrenoceptor antagonist in rat thoracic aorta

Ocoteine, isolated from Cassytha filiformis, was found to be an alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of phenylephrine-induced vasoconstriction (pA2 = 7.67 +/- 0.09). Removal of endothelium from the aorta did not affect its antagonistic potency (pA2 = 7.97 +/- 0.07). [3H]-Inositol monophosphate formation caused by noradrenaline (3 microM) was suppressed by ocoteine (10 microM) and prazosin (3 microM). Ocoteine did not affect the contraction induced by U-46619, prostaglandin F2 alpha or angiotensin II, but inhibited slightly those by high K+ and endothelin I. Neither the cyclic AMP nor cyclic GMP content of rat thoracic aorta was changed by ocoteine (10 microM). Comparing the EC50 values, the potency of ocoteine against 5-hydroxytryptamine (5-HT) was about 60 times less than that against phenylephrine. Ocoteine (10 microM) also slightly antagonized the clonidine-induced inhibition of the twitch response evoked by field stimulation in rat vas deferens. In guinea pig trachea, the contraction caused by carbachol, histamine, neurokinin A or leukotriene C4 and beta 2-adrenoceptor-mediated relaxing responses induced by isoprenaline were not affected by ocoteine (10 microM). The voltage clamp study in rat ventricular single myocytes revealed that ocoteine (3, 10 microM) inhibited steady state outward currents, but not transient outward currents or slow inward Ca2+ currents. It is concluded that ocoteine is a selective alpha 1-adrenoceptor antagonist in isolated rat thoracic aorta. At high concentrations, it also blocks 5-HT receptors and Na+ and steady state outward currents in rat ventricular myocytes.

Determination of boldine in plasma by high-performance liquid chromatography

A sensitive method for the determination of boldine in blood plasma is described. The procedure involves a direct pH-buffered chloroform extraction of boldine from blood plasma, followed by its assay under isocratic conditions by HPLC with UV detection. The extraction recovery is excellent, and sensitivity and precision of the method are very high, when applied to plasma samples containing pharmacologically relevant concentrations of boldine.

Effects of thaliblastine on cytotoxicity and DNA damage in drug-sensitive and -resistant rat ovarian tumor cells treated with cisplatin

Combination effects of cisplatin (DDP) and thaliblastine (TBL) in DDP-sensitive (0-342) and -resistant (0-342/DDP) rat ovarian tumor cells were investigated. TBL alone, at either 40 or 80 micrograms/ml, exerted higher cytotoxicity in the DDP-resistant 0-342/DDP cells than in the parental sensitive 0-342 cells in growth inhibition assay (% inhibitions: 12.5 and 42.8 in 0-342 cells vs. 37.5 and 66.1 in 0-342/DDP cells, at 40 and 80 micrograms/ml of TBL, respectively). TBL at 40 micrograms/ml showed an additive effect with DDP in the sensitive cells, while a synergistic cytotoxicity was observed in the resistant subline when the two drugs were used in combination, as exhibited by either % inhibition or cell viability. At 80 micrograms/ml of TBL, however, the combination effects were less than additive (infraadditive) in both lines, but still this treatment was more cytotoxic in 0-342/DDP cells. Alkaline elution assay showed that DDP induced higher DNA interstrand crosslings (ISCL) in 0-342 cells, while TBL produced DNA single strand breaks (SSB) in a dose-dependent manner in the resistant line but not in the sensitive cells. Combination of these two compounds resulted in a dramatic increase of DNA-SSB in 0-342/DDP cells. It is tentatively concluded that TBL might have some potential in combination with DDP to conquer the resistance in clinical use, which may result from its selective SSB-inducing activity in the resistant cells.

Haemodynamic effects of dicentrine, a novel alpha 1-adrenoceptor antagonist: comparison with prazosin in spontaneously hypertensive and normotensive Wistar-Kyoto rats

1. The haemodynamic effects of dicentrine, an aporphine derivative isolated from the plant Lindera megaphylla, were investigated and compared with prazosin in rats. 2. In anaesthetized normotensive Wistar-Kyoto (WKY) rats, i.v. administration of dicentrine (0.1, 0.5, 1.0 mg kg-1) and prazosin (0.01, 0.05, 0.1 mg kg-1) induced a dose-related reduction of mean arterial pressure (MAP) which reached a maximal effect 5-10 min after injection and persisted for 2 h. 3. In anaesthetized WKY rats, a higher dose of dicentrine (1.0 mg kg-1, i.v.) did not cause any significant changes in heart rate (HR), cardiac output (CO) and stroke volume (SV) but markedly increased tail blood flow. In contrast, a higher dose of prazosin (0.1 mg kg-1, i.v.) produced a decrease in HR which paralleled the time course of the hypotensive response. 4. The hypotensive activity of dicentrine was completely abolished by alpha-adrenoceptor blockade. Both dicentrine and prazosin significantly attenuated pressor responses to noradrenaline but failed, even at maximal hypotensive doses, to impair the pressor effects of angiotensin II or vasopressin. These observations suggest that dicentrine appears to exert its hypotensive action through alpha 1-adrenoceptor blockade. 5. In conscious normotensive and spontaneously hypertensive (SH) rats, dicentrine (0.5-2.0 mg kg-1, i.v.) and prazosin (0.05-0.2 mg kg-1, i.v.) also evoked dose-related decreases in MAP which were of greater magnitude in SH rats. Oral administration of dicentrine (5 and 8 mg kg-1) to conscious SH rats caused a hypotensive effect which persisted for over 15 h.6. These results suggest that dicentrine may have therapeutic potential as an oral antihypertensive drug via alpha-adrenoceptor blockade.

Antiproliferative activity of the non-myelotoxic antitumour agent of plant origin, Thaliblastine, on two human glioma cell lines

The antiproliferative activity of the non-myelotoxic antitumour agent of plant origin, Thaliblastine, on two human glioma cell lines is described. Thaliblastine was added once one day following start of culture; proliferation was monitored over 7 days. The antiproliferative activity of Thaliblastine was strongly dependent on concentration and time of incubation. The ID50 of Thaliblastine in T406 and GW27 glioma lines was 5.1 micrograms/ml and 8.2 micrograms/ml (7.0 microM and 11.2 microM), respectively.

Interaction of 99mTc-labeled liposomes with Walker tumour cells in vitro. Liposome-mediated introduction of thaliblastine into resistant Walker tumour cells

A method for labeling phospholipid vesicles (liposomes) with 99mTc-pertechnetate is described. The labeling methodology involves the chemical reduction of sodium 99mTc-pertechnetate by stannous chloride, which produces a 99mTc-SnCl2 complex with high binding capacity to phospholipids. Binding studies in vitro showed that Walker tumour cells can incorporate large amounts of 99mTc-labeled liposomes without cytotoxic effects. Fusion of liposomes with the cell plasma membrane may represent an important pathway for lipid incorporation. A Walker cell line resistant to thaliblastine, on treatment with the antitumour alkaloid thaliblastine entrapped in liposomes, showed a marked growth inhibition at concentrations that had little effect when used as free drug. The usefulness of 99mTc-labeled liposomes for kinetic binding studies with tumour cells in cultures and their possible use as carriers of cytotoxic agents in selective cancer chemotherapy, are discussed.

Preliminiary data on the pharmacokinetics of glaziovine in man

The pharmacokinetic parameters of Glaziovine, a pro-aporphine alkaloid with neuropharmacological properties, were investigated in healthy human volunteers. Glaziovine-14C 20 mg was administered in capsules (oral route) and in vials (i.v. route). Total radioactivity was meausred in plasma, urine and faeces. When administered orally, peak plasma levels were encountered at 2 h. The cumulative urinary excretion of total radioactivity over a 24 h period was 38% after oral and 50% after i.v. administration. Investigation of metabolites in urine revealed Glaziovine glucuronide as the sole metabolite of the drug. By comparing the percentage of urinary excretion or the area under the plasma level-time curve (AUC) obtained in the first 24 hours after i.v. and oral administration, enteral absorption was found to range from 78 to 84%. Thus, glaziovine appears to show very high enteratral absorption.

Effects of intravenous kainic acid, N-methyl-D-aspartate, and (--)-nuciferine on the cat spinal cord

Kainic acid (a rigid conformational analogue of glutamate), N-methyl-D-aspartate (the methylated derivative of aspartate), and (--)-nuciferine (an aporphine alkaloid with a depressant effect on glutamate-induced neuronal firing), which, so far, have been examined in microiontophoretic studies, were investigated in spinal cats for their effects on some spinal cord activities after intravenous injections. At low doses, kainic acid (0.3 mg kg-1) enhanced segmental monosynaptic but not polysynaptic ventral root reflexes and increased the excitability of motoneurones, whereas N-methyl-D-aspartate (3 mg kg-1) facilitated polysynaptic but not monosynaptic reflexes. Higher doses of the two amino acids depolarized motoneurones and primary afferent endings, enhanced monosynaptic reflexes and depressed polysynaptic reflexes. (--)-Nuciferine (1--10 mg kg-1) depressed monosynaptic but not polysynaptic ventral root reflexes in a dose-dependent manner and antagonized the effects of kainic acid but not of N-methyl-D-aspartate on the spinal cord. The results are consistent with the hypothetical excitatory transmitter role of glutamate in primary afferents and of aspartate in excitatory spinal cord interneurones; the findings also suggest that (--)-nuciferine may be used as a systemically effective, rather selective blocker of central glutamate receptors.

Absorption, fate and excretion of glaziovine-14C in the dog

The pharmacokinetic parameters of glaziovine, a proaporphine alkaloid with neuropharmacological properties, were investigated in dogs. At alkaline pH, glaziovine-14C showed a very high partition coefficient value from a buffered water solution and both benzene and chloroform. When administered i.v. to both conscious and anaesthetized dogs, levels of glaziovine-14C were higher in the heart, liver, kidneys and brain, and lower in skeletal muscle, skin and plasma. The high amount of radioactivity found in the small intestine as well as that found in bile obtained from a biliary fistula demonstrates that glaziovine is excreted both via the bile and via urine in not dissimilar amounts at least in dogs. When administered orally, peak plasma levels were encountered in 1 hr. Cumulative urinary excretion of glaziovine over a 24 hr period was 49% after the i.v. route and 39% after the oral route. By comparing the percentage of urinary excretion or the area under the plasma level time curve (AUC) obtained in the first 24 hr after i.v. and oral administration, percentages of bioavailability were obtained ranging from 80 to 98%. Glaziovine thus seems to possess a very high enteral absorption.

Aporphines, 21. (1,2) Dopaminergic activity of aporphine and benzylisoquinoline derivatives. Synthesis of 8-hydroxyaporphines and 1-(hydroxybenzyl)-2-n-propyl-1,2,3,4-tetrahydroisoquinolines

The synthesis and physical properties of 8-hydroxyaporphine (3a) and 8-hydroxy-N-n-propylnoraporphine (3b) are described. The replacement of the rigid aporphine ring system by the more flexible benzyltetrahydroisoquinoline moiety, still containing all the necessary substitutents of the potent dopamine agonist N-n-propylnorapomorphine (1b) (NPA), resulted in the synthesis of 1-(3,4-dihydroxybenzyl)-2-propyl-1,2,3,4-tetrahydroisoquinoline (4). Analogous to 4,1-(4-hydroxybenzyl)-2-propyl-1,2,3,4-tetrahydroisoquinoline (5) was synthesized for a direct comparison with the biological activity of the corresponding 10-hydroxyaporphine (2). All compounds synthesized were evaluated as salts of their racemates. In animals with unilateral 6-OHDA lesion of the nigrostriatal pathway, (-)NPA and 2 caused dose-dependent contralateral circling behavior although activity was greatly reduced for the monohydroxylated aporphine 2. 3b,4, and 5 were inactive at doses of 0.25-4.0 mg/kg sc. Compounds 2 and 3b exhibited very weak activity in the stereotype tests in comparison to the response obtained with apomorphine and (-)-NPA. 4 and 5 failed to induce any sterotyped response. These compounds were also investigated for their ability to stimulate locomotor activity following direct injection into the nucleus accumbens. (-)-NPA induced a modest increase in activity but apomorphine completely failed to elicit a locomotor responses and antagonized the effect induced by dopamine. 2,3b, 4 and 5 neither enhanced locomotor activity on direct injection into the nucleus accumbens nor antagonized the hyperactivity response to intraacumbens dopamine when administered peripherally. On direct injection into the caudate-putamen only apomorphine induced stereotyped biting; (-)-NPA, 2, 3b, 4, and 5 were inactive. The differential activity of the aporphine derivatives in these tests strongly supports the possible existence of different types of dopamine receptors within the extrapyramidal and mesolimbic systems. The present studies confirm that the flexible benzylisoquinolines 4 and 5 do not adopt the active dopamine conformation and that the rigid aporphines, preferably containing hydroxyl functions at the 10 or 11 positions, are of greater importance in eliciting potent dopamine agonist activity.

Phase I study of thalicarpine (NAC-68075), a plant alkaloid of noval structure

An initial clinical trial of daily and weekly X 6 ihtravenous infusions of thalicarpine, a plant alkaloid of novel structure, was carried out in 36 patients. Twenty-eight patients received 33 courses of single-dose administration at doses of 200-1900 mg/m2. At the maximum tolerable dose of 1400 mg/m2, toxic effects included arm pain (nine or ten), central nervous system depression (seven of ten), nausea and vomiting (two of ten), hypotension (two of ten), hypertension (two of ten), arrhythmia (premature ventricular contractions) (one of ten), and electrocardiographic changes (mainly T-wave flattening) (five of ten). At the maximum tolerable dose for weekly administration, 1100 mg/m2/week X 6, arm pain was seen in seven of eight, central nervous system depression in three of eight, hypotension in one of eight, and electrocardiographic changes in three of eight. The recommended dose for phase II trials is 1100 mg/m2/week by a 2-hour intravenous infusion.