Rauniticine-allo-oxindole B and rauniticinic-allo acid B, new heteroyohimbine-type oxindole alkaloids from the stems of Malaysian Uncaria longiflora var. pteropoda

Two new heteroyohimbine-type oxindole alkaloids, rauniticine-allo-oxindole B and rauniticinic-allo acid B, have been successfully isolated from the stems extract of Malaysian Uncaria longiflora var. pteropoda. The structures of the two new alkaloids were determined by spectroscopic analysis.

Tethered yohimbine analogs as selective human alpha2C-adrenergic receptor ligands

Yohimbine is a potent and relatively nonselective alpha(2)-adrenergic receptor (AR) antagonist. In an earlier report, we demonstrated that dimeric yohimbine analogs containing methylene and methylene-diglycine tethers were highly selective human alpha(2C)-AR ligands. Little work has been done to examine the role of the tether group or the absence of the second yohimbine pharmacophore on selectivity for human alpha(2)-AR subtypes. The goal of our study was to determine the binding affinities and functional subtype selectivities of a series of tethered yohimbine ligands in the absence of the second pharmacophore. The profiles of pharmacological activity for the yohimbine analogs on the three human alpha(2)-AR subtypes expressed in Chinese hamster ovary cells were examined using receptor binding and cAMP inhibition assays. All of the tethered yohimbine analogs exhibited higher binding affinities at the alpha(2C)- versus alpha(2A)- and alpha(2B)-AR subtypes. Notably, the benzyl carboxy alkyl amine and the carboxy alkyl amine analogs exhibited 43- and 1995-fold and 295- and 54-fold selectivities in binding to the alpha(2C)- versus alpha(2A)- and alpha(2B)-ARs, respectively. Data from luciferase reporter gene assays confirmed the functional antagonist activities and selectivity profiles of selected compounds from the tethered series. The data demonstrate that the second pharmacophore may not be essential to obtain alpha(2C)-AR subtype selectivity, previously observed with the dimers. Further changes in the nature of the tether will help in optimization of the structure-activity relationship to obtain potent and selective alpha(2C)-AR ligands. These compounds may be used as pharmacological probes and in the treatment of human disorders.

Human sympathetic activation by alpha2-adrenergic blockade with yohimbine: Bimodal, epistatic influence of cytochrome P450-mediated drug metabolism

BACKGROUND

alpha2-Adrenergic blockade responses suggest adrenergic dysfunction in hypertension. alpha2-Blockade is also used to treat autonomic dysfunction. However, pharmacokinetic determinants of yohimbine disposition are not understood.

METHODS

We evaluated alpha2-blockade with intravenous yohimbine in 172 individuals. Specific cytochrome P450 (CYP) isoform-mediated metabolism was investigated. Results were evaluated by ANOVA and by maximum likelihood analysis for bimodality of response distributions.

RESULTS

Yohimbine metabolism to 11-hydroxy-yohimbine displayed greater than 1000-fold variability, with 17 individuals showing no metabolism. Nonmetabolizers differed from others in ethnicity but not in age, sex, body habitus, blood pressure, heart rate, or family history of hypertension. Bimodality of metabolism was suggested by frequency histogram, as well as maximum likelihood and cluster analysis. Among ethnic groups, subjects of European ancestry had the highest frequency of nonmetabolism. In vitro oxidation suggested that the major route of metabolism (lowest Michaelis-Menten constant and greatest intrinsic clearance) was likely via CYP2D6 to 11-hydroxy-yohimbine. In vivo genotypes at both CYP2D6 and CYP3A4 were necessary to predict metabolism (overall F = 3.03, P =.005); an interaction of alleles at these 2 loci (interaction F = 3.05, P =.033) suggested an epistatic effect on drug metabolism in vivo. Nonmetabolizers had greater activation of sympathetic nervous system activity. Yohimbine increased blood pressure, an effect mediated hemodynamically by elevation of cardiac output rather than systemic vascular resistance. Blood pressure and cardiac output responses did not differ by metabolizer group.

CONCLUSIONS

We conclude that heterogeneous, bimodally distributed yohimbine metabolism depends on common genetic variation in both CYP2D6 and CYP3A4 and contributes to differences in sympathetic neuronal response to alpha2-blockade. These results have implications for both diagnostic and therapeutic uses of this alpha2-antagonist.

Catharanthus roseus L. plants and explants infected with phytoplasmas: alkaloid production and structural observations

The results of several experiments concerning the presence and composition of alkaloids in different tissues (stems, leaves, roots) of Catharanthus roseus L. plants and explants, healthy and infected by clover phyllody phytoplasmas, are reported. The alkaloids extracted and determined by the reverse phase high-pressure liquid chromatography were vindoline, ajmalicine, serpentine, vinblastine, and vincristine. The total alkaloid concentration was higher in infected plants than in the controls, in particular the increase of vinblastine in infected roots was very significant. The ultrastructural observations of infected roots showed alterations of the cell walls and of the nuclei. These results demonstrate that phytoplasmas, detected in all infected tissues by light fluorescence and transmission electron microscopy, play an important role on secondary metabolism of the diseased plants, modifying both the total content of alkaloids and their ratio.

A New 9-Methoxyyohimbine-Type Indole Alkaloid from Mitragyna africanus

A new yohimbine-type indole alkaloid (1). was isolated from the stem bark of Mitragyna africanus (WILLD.) collected in Nigeria, along with known seven Corynanthe-type oxindole alkaloids, two secoiridoids, three lignans, and a quinovic acid derivative. Their structures were elucidated by spectroscopic analyses.

Studies on production of ajmalicine in shake flasks by multiple shoot cultures of Catharanthus roseus

The effects of different concentrations of indole-3-acetic acid (IAA) and benzyladenine (BA) on production of ajmalicine by multiple shoot cultures of Catharanthus roseus (C. roseus) were studied. By supplementing Murashige and Skoog's (MS) medium with a high concentration of IAA (11.42 microM) and a low concentration of BA (2.22 microM), shoot cultures accumulated high levels of ajmalicine. When culture medium was fortified with a low concentration of IAA (2.85 microM) and a high concentration of BA (8.90 microM), shoots released high levels of ajmalicine into the culture medium. Quantification of ajmalicine was performed by high performance liquid chromatography (HPLC). The highest concentration of ajmalicine production (0.166% dry wt) was obtained by shoot cultures grown in MS medium containing IAA (11.42 microM) on 20 days of cultivation. Shoot cultures accumulated ajmalicine 4.2-fold more in IAA (11.42 microM) supplemented medium compared with the high concentration of BA (8.90 microM). The content of ajmalicine concentration in the medium was quantified. Shoot cultures grown in BA (8.90 microM) supplemented medium released the maximum production of ajmalicine (0.853 g/L) into the culture medium after 15 days of cultivation. The experimental data show that the secretion of ajmalicine was 2-fold more into the culture medium supplemented with a high concentration of BA compared to that with a low concentration of BA. Data presented here show that production of ajmalicine by shoot cultures is not correlated with growth rate. Dimeric indole alkaloids vincristine and vinblastine were not present in shoot cultures. Ajmalicine production by shoot cultures was 2.4-fold higher compared to leaves of 1-year-old naturally grown plants.

Production of ajmalicine and ajmaline in hairy root cultures of Rauvolfia micrantha Hook f., a rare and endemic medicinal plant

Hairy roots of Rauvolfia micrantha were induced from hypocotyl explants of 2-3 weeks old aseptic seedlings using Agrobacterium rhizogenes ATCC 15834. Hairy roots grown in half-strength Murashige & Skoog (MS) medium with 0.2 mg indole 3-butyric acid l-1 and 0.1 mg alpha-naphthaleneacetic acid l-1 produced more ajmaline (0.01 mg g-1 dry wt) and ajmalicine (0.006 mg g-1 dry wt) than roots grown in auxin-free medium. Ajmaline (0.003 mg g-1 dry wt) and ajmalicine (0.0007 mg g-1 dry wt) were also produced in normal root cultures. This is the first report of production of ajmaline and ajmalicine in hairy root cultures of Rauvolfia micrantha.

Plant-cell bioreactors with simultaneous electropermeabilization and electrophoresis

Experimental investigations on using low-level electric currents and voltages to extract, transport, and collect intracellular secondary metabolites from plant cells while maintaining their viabilities were conducted focusing on the production of: (1) ionic betalains, mainly negatively-charged betanin, from Beta vulgaris cells, and (2) ionic alkaloids, particularly positively-charged ajmalicine and yohimbine, from Catharanthus roseus cells. Three versions of tubular membrane reactors in which electropermeabilization of cell membranes and electrophoresis and diffusion of ionic products take place simultaneously, with or without convective flow, to achieve desirable extraction were developed. Concentrations of secondary metabolites produced from these plant-cell reactors under steady and oscillatory electrical forcings were recorded and the viabilities of treated cells examined. Oscillatory application of electrical field appears to produce more products while retaining higher cell viability.

Yohimbine dimers exhibiting selectivity for the human alpha 2C-adrenoceptor subtype

Yohimbine is a potent and selective alpha2- versus alpha1-adrenoceptor antagonist. To date, drugs with high specificity for the alpha2-adrenoceptor show marginal selectivity among the three alpha2-adrenoceptor subtypes. Initial studies showed that yohimbine was about 4- and 15-fold more selective for the human alpha2C-adrenoceptor in comparison with the alpha2A- and alpha2B-adrenoceptors, respectively. To improve on this alpha2-adrenoceptor subtype selectivity, a series of yohimbine dimers (varying from n = 2 to 24 spacer atoms) were prepared and evaluated for receptor binding on human alpha2-adrenoceptor subtypes expressed in Chinese hamster ovary cells. Each dimeric analog showed higher affinities for alpha2A- and alpha2C-adrenoceptor versus the alpha2B-adrenoceptor; and yohimbine dimers with spacers of n = 2, 3, 4, 18, and 24 exhibited selectivity for the alpha2C-adrenoceptor. The yohimbine dimers n = 3 and n = 24 showed the highest potency and selectivity (32- and 82-fold. respectively) for the alpha2C-adrenoceptor in receptor binding and in functional studies (42- and 29-fold, respectively) measuring cAMP changes using a cell-based luciferase reporter gene assay. The dimers (n = 3 and n = 24) had high selectivity (>1000-fold) for the alpha2C-adrenoceptor compared with the three alpha1-adrenoceptor subtypes. These findings demonstrate that the addition of spacer linkages to bivalent yohimbine molecules provides a successful approach to the development of ligands that are potent and highly selective for the alpha2C-adrenoceptor.

The effect of ajmalicine spiking and resin addition timing on the production of indole alkaloids from Catharanthus roseus cell cultures

The potential for the feedback inhibition of indole alkaloid synthesis was investigated by spiking suspension cultures of Catharanthus roseus with 0, 9, or 18 mg/L ajmalicine on day 0. The production of ajmalicine, catharanthine, and serpentine were inhibited in a dose-dependent manner. The inhibition was transient as the exogenous ajmalicine was ultimately either metabolized in the medium or within the cell. The addition of neutral resin has previously been shown to enhance ajmalicine production. To minimize product inhibition and product metabolism, Amberlite XAD-7 resin was added to immobilized cultures of C. roseus starting on either day 0, 5, or 15, and fresh resin was exchanged for spent resin every 5 days. The addition of resin did not decrease the viability of the culture. Growth was reduced only in cultures with resin added on day 0. Alkaloid production was enhanced to different extents by the timing of resin addition, suggesting that feedback inhibition or product metabolism was present throughout the culture period. Ajmalicine recovery was nearly 100% when the resin was added initially either on day 0 or day 5. Ajmalicine recovery was reduced to 55% when the resin was added later in the culture period starting on day 15, presumably because of resin saturation or the inaccessibility of alkaloids trapped in the vacuole. Delaying the addition of XAD-7 resin until 5 days after the start of the culture resulted in the highest improvement in ajmalicine production, i.e approximately 70% and also resulted in the complete recovery of ajmalicine from the cell.

[Effect of almitrine/raubasine on cerebral metabolism in the elderly]

Recent neurobiological data has led to renewed interest in oxygen (O2). The discovery of neuroglobin, protein varyingly present in the brain, has been enhanced by the elucidation of the mechanisms through which oxygen intervenes in neuronal metabolism. Almitrine/raubasine activates the metabolism of hypoxic/ischemic neurones by increasing O2 bioavailability. This mechanism supports the effects on behaviour obtained in various animal models and the benefits observed during clinical trials in elderly patients presenting with cognitive defects.

Influence of fungal elicitors on production of ajmalicine by cell cultures of Catharanthus roseus

Suspension cultures of Catharanthus roseus (C. roseus) were elicited with fungal cell wall fragments of Aspergillus niger (A. niger), Fusarium moniliforme (F. moniliforme), and Trichoderma viride (T. viride). The effects of elicitor dosage, exposures time, and age of subculture on ajmalicine accumulation were studied. A higher concentration of elicitor extract responded positively to C. roseus suspension cultures. Ajmalicine accumulation increased by about 3-fold when cells were treated with A. niger, F.moniliforme, and T. viride. The maximum ajmalicine production (75 microg g(-1) dry weight (DW)) was observed in cells treated with T. viride. Cell cultures were elicited with 5% preparation of A. niger, F. moniliforme, and T. viride and exposed for 24, 48, 72, and 96 h. for elicitation. Suspension cultures elicited with T. viride for 48 h showed a 3-fold increase (87 microg g(-1) DW) in ajmalicine contents, whereas A. niger and F. moniliforme synthesized a 2-fold increase in alkaloid and yielded 52 and 56 microg g(-1) DW ajmalicine, respectively. C. roseus cells of different age (5,10, 15, 20, and 25 days old) were treated with a 5% elicitor of A. niger, F. moniliforme, and T. viride and investigated elicitors activity at different age of cell cultures. Maximum yield 166 microg g(-1) DW of ajmalicine was synthesized in 20 day old suspension cultures treated with T. viride. A longer period of incubation of cell cultures with elicitors adversely affected the ajmalicine synthesis.

Effects of stress factors, bioregulators, and synthetic precursors on indole alkaloid production in compact callus clusters cultures of Catharanthus roseus

Compact callus cluster (CCC) cultures established from Catharanthus roseus consist of cohesive callus aggregates displaying certain levels of cellular or tissue differentiation. CCC cultures synthesize about two-fold more indole alkaloids than normal dispersed-cell cultures. Our studies here show that additions of KCl, mannitol, and a variety of synthetic precursors and bioregulators to the CCC cultures markedly improved indole alkaloid production and release of these alkaloids into the medium. Treatment with 250 mM mannitol and 4 g/l KCl yielded 42.3 mg l(-1) and 33.6 mg l(-1)of ajmalicine, respectively; these amounts were about four-fold higher than the control. Succinic acid, tryptamine, and tryptophan feedings also significantly increased ajmalicine (41.5 mg l(-1), 36.9 mg l(-1), and 31.8 mg l(-1), respectively) and catharanthine (21.1 mg l(-1), 17.2 mg l(-1), and 18 mg l(-1), respectively) production by the CCC cultures, while geraniol feeding inhibited biomass and alkaloid accumulation. We also found that tetramethyl ammonium bromide could significantly improve ajmalicine production (49.3 mg l(-1)) and catharanthine production (18.3 mg l(-1)) in C. roseus CCC cultures. The mechanisms responsible for these treatment effects are discussed herein.

Hydroxylation of yohimbine in superacidic media: one-step access to human metabolites 10 and 11-hydroxyyohimbine

Two major human metabolites of yohimbine (1), 10- and 11-hydroxyyohimbine (2 and 3), were prepared by direct hydroxylation of 1 under superacidic conditions. In this medium, the four positions of the benzene part of yohimbine were hydroxylated and the corresponding monohydroxylated compounds (2-5) were isolated. The structures of 2-5 were elucidated by spectroscopic methods including 1D and 2D NMR techniques.

The effect of inoculum density and conditioned medium on the production of ajmalicine and catharanthine from immobilized Catharanthus roseus cells

The effect of the cell-inoculum size and the addition of conditioned medium on ajmalicine and catharanthine production were studied using immobilized Catharanthus roseus cells. Higher specific-uptake rates of ammonium, nitrate, and sugars were observed in the low-inoculum-density cultures (50 g FW/L) compared to the high-inoculum-density cultures (100 g FW/L). Alkaloid production was not correlated with the exhaustion of a particular nutrient from the medium. The high-inoculum-density cultures produced higher ajmalicine concentrations throughout the experiment. Catharanthine production was similar between the two inoculum-density cultures. The addition of conditioned medium to MS-production medium dramatically improved the production of ajmalicine and catharanthine. The addition of conditioned medium enhanced ajmalicine production from immobilized Catharanthus roseus cultures on day 15 by at least two- to fourfold compared to media without the conditioning factors. Catharanthine production was increased by nearly fivefold in cultures with conditioned medium compared to those without conditioned medium. The enhancing effects of conditioned medium on alkaloid production were attributed to an unidentified factor produced and secreted by suspension cultures of C. roseus. The presence of conditioned medium also decreased the sucrose hydrolysis rate. The ajmalicine concentration in these immobilized cell cultures was found to be a function of the fresh-weight concentration, irrespective of the inoculum density or the culture medium. The medium choice and the inoculum density determined how rapidly fresh weight was accumulated and thus, how quickly ajmalicine was produced. Ajmalicine production correlated positively with fresh-weight concentration, but catharanthine production was not correlated with fresh-weight concentration.

Characterization of a new radioiodinated probe for the alpha2C adrenoceptor in the mouse brain

[125I]17alpha-hydroxy-20alpha-yohimban-16beta-(N-4-p6 hydroxyphenethyl)carboxamide or [125I]rauwolscine-OHPC, a new radioiodinated probe derived from rauwolscine was synthesized and its binding characteristics investigated on sections of the mouse caudate putamen. [125I]rauwolscine-OHPC binding was saturable and revealed interaction with a single class of binding sites (KD= 0.171 nM, Bmax = 3082 pCi/mg of tissue). The kinetically derived affinity was in close agreement with the affinity evaluated by saturation experiments: k(-1)/k(+1)(0.0403 min(-1)/114 10(6) M(-1) min(-1))=0.35 nM. Competition studies revealed interaction with one single class of binding sites for each of the twelve compounds tested. The rank of potency suggested an interaction with alpha2 adrenoceptors (atipamezole > or = RX 821002 > yohimbine > (-)epinephrine). Moreover, the good affinity of [125I] rauwolscine-OHPC binding sites for spiroxatrine, yohimbine, WB 4101, the relatively good affinity for prazosin (Ki =37.4 nM) and the affinity ratio prazosin/oxymetazoline (37.4/43.4=0.86) were consistent with an alpha2C selective labelling of [125I]rauwolscine-OHPC. The distribution of [125I]rauwolscine-OHPC binding sites in mouse brain was characterized by autoradiography. The density of binding sites was high in the islands of Calleja, accumbens nucleus, caudate putamen and olfactory tubercles, moderate in the hippocampus, amygdala and anterodorsal nucleus of the thalamus. These findings demonstrated that [125I]rauwolscine-OHPC is a useful radioiodinated probe to label alpha2C adrenoceptors in mouse brain.

A simple structured model for maintenance, biomass formation, and ajmalicine production by nondividing Catharanthus roseus cells

The stoichiometry of maintenance and carbohydrate storage as well as ajmalicine production kinetics of non-dividing Catharanthus roseus cells in the second stage of a two-stage batch process were investigated. For the mathematical description of these processes, a simple structured model with 5 parameters is proposed. In the model the biomass is divided in two compartments: active biomass and storage carbohydrates. In induction medium (standard medium without phosphate, nitrogen and hormones), biomass formation, glucose consumption, and CO(2) production appeared to be constant in time. Therefore, it is assumed that the active biomass level is constant. The maintenance coefficient m(S), and the yield of storage carbohydrates on glucose Y(SC) were optimized by fitting the model on experimental data: 0.003 C-mol/C-mol/h and 0.82 C-mol/C-mol, respectively. Production kinetics were incorporated in this model and related to the active biomass fraction. The maximum specific ajmalicine production rate q(p)(max) was fitted on the data: 7.5 micromol/C-mol/h. The model was tested at several different experimental conditions, and proved to describe the experimental results adequately. An independent experiment at a very high cell density in order to obtain maximum product formation was used to validate the model. It provided a satisfactory description of the results, but the final ajmalicine concentration (198 micromol/L after 18 days) was lower than the calculated maximum, due to accumulation of inhibiting gaseous metabolites.

Biopharmaceutics and metabolism of yohimbine in humans

The biopharmaceutics of yohimbine (YO) and the pharmacokinetics of 10-hydroxy-yohimbine (10-OH-YO) and 11-hydroxy-yohimbine (11-OH-YO) were investigated in healthy subjects following i.v. (5 mg) and oral (8 mg) dosing. One subject was found as a slow hydroxylator of YO. The mean (+/-S.D.) oral absolute bioavailability of YO was 22.3+/-21. 5%. Total plasma clearance (CL) and renal clearance (CL(r)) of YO following i.v. dosing were 0.728+/-0.256 ml/min and 0.001+/-0.002 ml/min, respectively. Based on the steady-state volume of distribution (V(ss)), YO had a relatively low distribution (V(ss) = 32.2+/-12.1 l). The overall renal excretion of YO, 10-OH-YO and 11-OH-YO, expressed as percent of the dose of YO administered, were not different following i.v. and oral dosing, and were around 0.1, 0.2 and 14%, respectively. Following i.v. dosing of YO, the mean apparent terminal half-life of 11-OH-YO (347+/-63 min) was almost four times higher than that of YO (91.0+/-33.6 min) suggesting an elimination rate-limited kinetics for 11-OH-YO.

Design and evaluation of nitrosylated alpha-adrenergic receptor antagonists as potential agents for the treatment of impotence

We designed and evaluated a new class of molecules, nitrosylated alpha-adrenergic receptor antagonists, as potential agents for the treatment of impotence. In in vitro studies with human and rabbit corpus cavernosum strips in organ chambers, the alpha-adrenergic receptor antagonists (alpha-ARAs) moxisylyte and yohimbine and their corresponding nitrosylated compounds, SNO-moxisylyte (NMI-221) and SNO-yohimbine (NMI-187), concentration-dependently relaxed endothelin-induced contraction. The nitrosylated compounds were significantly more potent than the parent alpha-ARA. In human tissues, the specific phosphodiesterase type 5 inhibitor zaprinast potentiated the relaxing effects of the nitrosylated compounds. Only nitrosylated compounds induced accumulation of cyclic GMP in rabbit corpus cavernosum strips. Yohimbine and NMI-187 demonstrated a potent alpha2-blocking activity, with no significant differences in pA2 values (8.9 versus 8.2, respectively). Moxisylyte and NMI-221 showed moderate potency in antagonizing phenylephrine contraction, with comparable pA2 values for both molecules (6.5 versus 6.6, respectively). alpha-Adrenergic receptor-binding studies showed similar binding affinities for the alpha-ARA and their corresponding nitrosylated compounds. In vivo, intracavernosal injection of nitrosylated molecules caused greater increases in intracavernosal pressure (NMI-221 versus moxisylyte) that were more long lasting than those of moxisylyte or yohimbine. There were no significant differences between nitrosylated and non-nitrosylated compounds in the magnitude of systemic mean arterial pressure decrease after intracavernosal injection. alpha-ARA and the nitrosylated compounds showed no pain-inducing activity as evaluated with the paw-lick model in mice. In summary, nitrosylated alpha-ARA have the dual functionalities of nitric oxide donors and alpha-ARA. These drugs induced penile erection in animals, suggesting their possible therapeutic value as agents for the local pharmacological treatment of impotence.

Transient studies of light-adapted cultures of hairy roots of Catharanthus roseus: growth and indole alkaloid accumulation

Cultures of C. roseus transgenic ("hairy") root clones LBE-6-1 and LBE-4-2 were adapted with periodic daily illumination to investigate the effect of light on growth and nutrient utilization, and the accumulation of the indole alkaloids. Light-adapted roots appeared green and had radially thickened morphology compared with dark-grown controls. Their growth rates were higher than dark-grown controls, with 45% lower doubling times: LBE-6-1, 3.6 days; LBE-4-2, 2.8 days. Relative to dark-grown controls, light-adapted growth increased the biomass (DW) of LBE-6-1 by 25%, but had no effect on the DW of LBE-4-2. The macronutrients NH4+, NO3-, Pi, and sugars, were depleted completely by light-adapted root cultures in that order. The specific and total levels of the indole alkaloid serpentine was enhanced and of tabersonine was lowered in both root clones, while the overall trends of growth and non-growth association of tabersonine and serpentine, respectively, remained unaltered by light adaptation. Ajmalicine accumulation was enhanced in LBE-6-1, but lowered in LBE-4-2; its accumulation was growth-associated in dark-grown LBE-6-1, but appeared non-growth associated in light-adapted cultures. The accumulation of tabersonine-related compounds, lochnericine, and hörhammericine exhibited growth-associated trends, and were either negatively affected or unaffected by light adaptation of LBE-6-1. Neither vindoline nor its precursor, deacetylvindoline, was detected.

Effect of modulators on the ATPase activity and vanadate nucleotide trapping of human P-glycoprotein

P-Glycoprotein (Pgp) is responsible for the energy-dependent efflux of many natural product oncolytics. Overexpression of Pgp may result in multidrug resistance (MDR). Modulators can block Pgp efflux and sensitize multidrug resistant cells to these oncolytics. To study the interaction of modulators with Pgp, Pgp-ATPase activity was examined, using plasma membranes isolated from the multidrug-resistant cell line CEM/VLB100. A survey of modulators indicated that verapamil, trifluoperazine, and nicardipine stimulated ATPase activity by 1.3- to 1.8-fold, whereas two others, trimethoxybenzoylyohimbine (TMBY) and vindoline, had no effect. Further evaluation showed that TMBY completely blocked the stimulation by verapamil of ATPase activity by competitive inhibition, with a Ki of 2.1 microM. When the effects of these two modulators on the formation of the enzyme-nucleotide complex important in the catalytic cycle were examined, verapamil increased the amount of vanadate-trapped 8-azido-[alpha-32P]ATP bound to Pgp by two-fold, whereas TMBY had no effect. Moreover, TMBY blocked the verapamil stimulation of vanadate-8-azido-[alpha-32P]ATP. Together, these data indicate that verapamil and TMBY bind to Pgp at a common site or overlapping sites, but only verapamil results in enhanced Pgp-ATP hydrolysis and formation of the vanadate-nucleotide-enzyme complex.

Cerebrospinal fluid and plasma disposition of yohimbine and 11-hydroxy-yohimbine in young and older healthy subjects, and Alzheimer's disease patients

OBJECTIVE

The plasma and cerebrospinal fluid (CSF) disposition of yohimbine (YO) and 11-hydroxy-yohimbine (11-OH-YO), after oral administration of a single dose of YO (0.65 mg.kg-1) were studied in young and older healthy subjects and in patients with Alzheimer's disease (AD).

RESULTS

Plasma disposition of YO displayed large variability; no significant differences among subject groups were observed. In contrast, 11-OH-YO Cmax and AUC were significantly lower in the older normal subjects than in the young normal or AD subjects. A strong positive correlation between CSF and plasma YO concentrations was observed. A weak positive correlation between CSF and plasma concentrations of 11-OH-YO was also observed. CSF to plasma concentration ratios for yohimbine and 11-OH-YO were low (approximately 2%).

A three-dimensional protein model for human cytochrome P450 2D6 based on the crystal structures of P450 101, P450 102, and P450 108

Cytochromes P450 (P450s) constitute a superfamily of phase I enzymes capable of oxidizing and reducing various substrates. P450 2D6 is a polymorphic enzyme, which is absent in 5-9% of the Caucasian population as a result of a recessive inheritance of gene mutations. This deficiency leads to impaired metabolism of a variety of drugs. All drugs metabolized by P450 2D6 contain a basic nitrogen atom, and a flat hydrophobic region coplanar to the oxidation site which is either 5 or 7 A away from the basic nitrogen atom. The aim of this study was to build a three-dimensional structure for the protein and more specifically for the active site of P450 2D6 in order to determine the amino acid residues possibly responsible for binding and/ or catalytic activity. Furthermore, the structural features of the active site can be implemented into the existing small molecule substrate model, thus enhancing its predictive value with respect to possible metabolism by P450 2D6. As no crystal structures are yet available for membrane-bound P450s (such as P450 2D6), the crystal structures of bacterial (soluble) P450 101 (P450cam), P450 102 (P450BM3), and P450 108 (P450terp) have been used to build a three-dimensional model for P450 2D6 with molecular modeling techniques. Several important P450 2D6 substrates were consecutively docked into the active site of the protein model. The energy optimized positions of the substrates in the protein agreed well with the original relative positions of the substrates within the substrate model. This confirms the usefulness of small molecule models in the absence of structural protein data. Furthermore, the derived protein model indicates new leads for experimental validation and extension of the substrate model.

[Separation and preparation of indole alkaloids in Lycorma delicatula White. by HPLC]

A HPLC method for separating and preparing indole alkaloids is described. HPLC conditions for analysis: BIO-RAD series 700 HPLC, model 700 data station, UV: model 1749 UV-VIS monitor, column: BIO-RAD Hi-pore RP318, 250 mm x 10 mm, mobile phase: 80% methanol-H2O(gradient), flow rate: 1.5 ml/min, detection wavelength: 254 nm. On the basis of spectral (1HNMR, 13CNMR, H-H COSY, MS, DEPT) and chemical evidence, the structures of two compounds were elucidated as beta-yohimbine (yohimban-16-carboxylic acid-17-hydroxy methylester (3 alpha, 16 alpha, 17 beta)) and ajmalicine (oxayohimban-16-carboxylic acid-16,17-didehydro-19-ethyl methyl ester (19 alpha)).

Enzymology of indole alkaloid biosynthesis in Catharanthus roseus

Indole alkaloids in Catharanthus roseus have been in focus because of their medicinal value. These alkaloids consist of an indole moiety provided by tryptamine and a terpenoid portion provided by the secologanin. The most important catharanthus alkaloids are vinblastine (VLB), vincristine (VCR) and ajmalicine. VLB and VCR are clinically useful anticancer agents whereas ajmalicine is used for the treatment of circulatory diseases. VCR and VLB are the most expensive because of their low abundance in the plant, and are formed by the coupling of monomeric indole alkaloids vindoline and catharanthine, catalysed by peroxidases. The pathway that lead to monomeric indole alkaloids involves more than 20 enzymes of which 16 enzymes have been isolated and characterized biochemically, and only three at the molecular level. The present state of knowledge on enzymes and genes involved in indole alkaloid biosynthesis and various aspects of their regulation has been discussed.

Prevalence of impaired responsiveness to epinephrine in platelets among Japanese

The responsiveness of platelets only to epinephrine was markedly impaired in 23/140 (16%) healthy Japanese. The impaired responsiveness was not altered by changes in time and environment. Circulating level of catecholamines did not affect the responsiveness of platelets to epinephrine. A pilot family study indicated a possible familial nature of the defect. 3H methyl-yohimbine binding studies indicated that this defect was due to the decreased number of alpha 2 adrenergic receptor. Despite the defect, the potentiating effect of epinephrine on platelet aggregation stimulated by a low dose of ADP was normal. This abnormality is not apparently associated with any bleeding disorders and the clinical implication is unknown at present. It is, however, essential to acknowledge the prevalence of such defect in pursuing research on platelets stimulated by epinephrine.

A structure-function relationship among reserpine and yohimbine analogues in their ability to increase expression of mdr1 and P-glycoprotein in a human colon carcinoma cell line

We previously showed that there is a structure-function relationship among reserpine and yohimbine analogues in their ability to inhibit the function of P-glycoprotein (P-gp) and reverse multidrug resistance (MDR). Because some P-gp inhibitors (e.g., verapamil and nifedipine) can increase mdr1 and P-gp expression in human colon carcinoma cell lines, we used our reserpine/yohimbine analogues to determine whether there was a structural requirement for this induction. We found that 10 microM reserpine increased both mdr1 and P-gp expression by 4-10-fold in 48 hr in a human colon carcinoma cell line that expresses moderate levels of mdr1 (LS180-Ad50) but not in several other cell lines that expressed no mdr1. The reserpine/yohimbine analogues rescinnamine, trimethoxybenzoylyohimbine, and LY191401 (compound G), all of which contain the three structural elements used to describe the MDR pharmacophore, also increased both mdr1 and P-gp expression significantly. Despite some exceptions, we found that there was a good association between the ability of these analogues to induce mdr1 and P-gp expression and their ability to reverse vinblastine and doxorubicin resistance, revealing a structure-function relationship for this phenomenon. The increased P-gp expressed by these cells appeared to be functional, as determined by flow cytometric detection of rhodamine 123 retention. The increased expression was suppressed by 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, an RNA synthesis inhibitor, whereas the protein synthesis inhibitor cycloheximide enhanced the expression several-fold, suggesting that induction of mdr1 by these analogues is regulated at both the transcriptional and post-transcriptional levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of ajmalicine in reserpine raw materials by liquid chromatography with fluorescence detection

A method is presented for determination of ajmalicine in reserpine raw materials by liquid chromatography (LC) with fluorescence detection. The sample is dissolved in a very small volume of chloroform, and the resulting solution is diluted with methanol. The reference solution of ajmalicine is prepared directly in methanol. For LC, a 30 cm long normal-phase column is used. The mobile phase is methanol containing a small volume of an aqueous solution of 1-pentanesulfonic acid, sodium salt. Detection is by fluorescence with excitation at 280 nm and emission at 360 nm. In 3 samples, the ajmalicine contents ranged from 1.2 to 1.9%.

Large-scale cultivation of Catharanthus roseus cells: production of ajmalicine in a 20-l airlift bioreactor

Bioreactor systems have been developed for the production of ajmalicine, an alkaloid used in the treatment of hypertension. Cell cultures of Catharanthus roseus produced higher levels of ajmalicine (323 micrograms g-1 dry weight) in a production medium enriched with tryptophan. The cell cultures were grown in medium prepared in tap water and market sugar with a view to minimise the costs of production. Large-scale cultivation of cell suspension was performed in a 20-l airlift bioreactor under controlled conditions. An ajmalicine production of 315 micrograms g-1 dry weight was achieved in the bioreactor after 14 d of cultivation.

2,4-D and alkaloid accumulation in periwinkle cell suspensions

Omission of 2,4-D from culture medium during one subculture of Catharanthus roseus cells, strain C20, resulted in an increased alkaloid accumulation, without effect on growth. Alkaloid accumulation, rather than growth, seemed to be more sensitive to 2,4-D. 2,4-D inhibited alkaloid accumulation essentially during growth phase, but its inhibitory effect during this period was partially reversible. As this reversibility was underlined only during the stationary phase, this suggested that this action could be situated upstream in a terpenoid non-specific pathway. 2,4-D feeding showed that inhibition is weaker and weaker as the alkaloid accumulation period proceeds. Auxin action during this period could take place downstream in specific alkaloid pathways. The lower alkaloid accumulation obtained after loganic acid feeding compared to that obtained with secologanin and loganin could indicate that loganic acid methylation should be one of the 2,4-D target(s).

Development of a pharmacophore for inhibition of human liver cytochrome P-450 2D6: molecular modeling and inhibition studies

To gain insight into the specificity of cytochrome P-450 2D6 toward inhibitors, a preliminary pharmacophore model was built up using strong competitive inhibitors. Ajmalicine (1), the strongest inhibitor known (Ki = 3 nM) was selected as template because of its rigid structure. The preliminary pharmacophore model was validated by performing inhibition studies with derivatives of ajmalicine (1) and quinidine (9). Bufuralol (18) was chosen as substrate and the metabolite 1'-hydroxybufuralol (19) was separated by high performance liquid chromatography. All incubations were carried out using human liver microsomes after demonstration that the Ki values obtained with microsomes were in accordance with those obtained with a reconstituted monooxygenase system containing purified cytochrome P-450 2D6. Large differences of Ki values ranging between 0.005 and 100 microM were observed. Low-energy conformers of tested compounds were fit within the preliminary pharmacophore model. The analysis of steric and electronic properties of these compounds led to the definition of a final pharmacophore model. Characteristic properties are a positive charge on a nitrogen atom and a flat hydrophobic region, the plane of which is almost perpendicular to the N-H axis and maximally extends up to a distance of 7.5 A from the nitrogen atom. Compounds with high inhibitory potency had additional functional groups with negative molecular electrostatic potential and hydrogen bond acceptor properties on the opposite side at respective distances of 4.8-5.5 A and 6.6-7.5 A from the nitrogen atom. The superposition of strong and weak inhibitors led to the definition of an excluded volume map. Compounds that required additional space were not inhibitors. This is apparently the first pharmacophore model for inhibitors of a cytochrome P-450 enzyme and offers the opportunity to classify compounds according to their potency of inhibition. Adverse drug interactions which occur when both substrates and inhibitors of cytochrome P-450 2D6 are applied may be predicted.

Alpha 2-adrenoceptor antagonist potencies of two hydroxylated metabolites of yohimbine

1. The alpha 2-adrenoceptor antagonist capacities of two hydroxylated metabolites of yohimbine in man (10-OH-yohimbine and 11-OH-yohimbine) were investigated on the alpha 2-adrenoceptors of human platelets and adipocytes and compared to those of yohimbine. 2. Yohimbine and 11-OH-yohimbine exhibited similar alpha 2-adrenoceptor affinity in biological studies i.e. inhibition of adrenaline-induced platelet aggregation and inhibition of UK14304-induced antilipolysis in adipocytes. 3. Yohimbine and the two metabolites displaced [3H]-RX 821002 binding with equivalent affinities in platelet and adipocyte membranes with the following order of potency: yohimbine > 11-OH-yohimbine > 10-OH-yohimbine. However, when binding studies were carried out in binding buffer supplemented with 5% albumin, the apparent affinity of yohimbine was reduced about 10 fold and was similar to that of 11-OH-yohimbine. 4. Yohimbine and its metabolites were bound to different extents to plasma proteins, the bound fraction being 82%, 43% and 32% respectively for yohimbine, 11-OH-yohimbine and 10-OH-yohimbine. 5. These results show that the main hydroxylated metabolite of yohimbine in man (11-OH-yohimbine) possesses alpha 2-adrenoceptor antagonist properties. The discrepancies found in binding studies (i.e. 10 fold lower affinity of 11-OH-yohimbine than yohimbine for alpha 2-adrenoceptors but similar capacities in blocking biological alpha 2-adrenoceptor effects in cells) are attributable to the higher degree of binding of yohimbine to plasma protein.

Induction of ajmalicine formation and related enzyme activities in Catharanthus roseus cells: effect of inoculum density

In Catharanthus roseus cell cultures the time courses of four enzyme activities, tryptophan decarboxylase (TDC), strictosidine synthase (SSS), geraniol-10-hydroxylase (G10H) and anthranilate synthase (AS), and alkaloid accumulation were compared under two different culture conditions (low-inoculum density and high-inoculum density on induction medium) and a control on growth medium. In growth medium a transient increase in TDC activity was first observed after which G10H reached its maximum activity; only tryptamine accumulated, no ajmalicine could be detected. Apparently, a concerted induction of enzyme activities is required for ajmalicine formation. Cells inoculated in induction medium showed such a concerted induction of AS, TDC and G10H activities. After 30 days the low-density culture had accumulated six times more ajmalicine (in mumoles/g) than the high-density culture. Thus, increase in biomass concentration (high-density cultures) did not enhance the total alkaloid production. The major differences observed in enzyme levels between high- and low-density cultures were in the AS and TDC activities, which were two to three times higher in the low-density culture, indicating that there is a positive correlation between ajmalicine formation and AS and TDC activities.

Neurologic and histologic evaluation of almitrine+raubasine (Duxil) in middle cerebral artery occlusion in cats

Impairment of energy metabolism is the fundamental mechanism leading to cell death in ischemia. Using the middle cerebral artery (MCA) occlusion model in cats, we studied the effect of Duxil (almitrine and raubasine combination), which was given either before and after or only after MCA occlusion, on ischemia in terms of neurological function and histological changes. Neurological function was assessed consecutively for 7 days after MCA occlusion using a categorical rating scale in 18 cats. Neurological function was significantly improved in treated animals than in non-treated controls regarding to the motor and sensory function, walking, posture and stepping reflex. Animals were killed on the 8th day and histological changes were examined by light and electron microscopies. Significant improvement in the morphological scores based on the light-microscopy changes were found in animals treated with Duxil compared to non-treated ones. Under the electron microscopy, the protective effects of Duxil were characterized by retaining glycogen and mitochondria. Morphological improvement was associated with the recovery of neurological function and especially profound in penumbra areas of MCA infarction. These results suggest that Duxil has a protective effect against ischemic damage induced by occlusion of MCA in cats.

Structure of a chiral intermediate in the synthesis of (+)-19-epiajmalicine

[2S*-(2 beta,3 alpha,6 alpha,12b beta)]-Methyl 3-acetyl-1,2,3,4,6,7,12,12b-octahydro-6-methoxycarbonyl-indolo+ ++[2,3-a] quinolizine-3-ethanoate, C22H26N2O5, M(r) = 398.46, orthorhombic, P2(1)2(1)2(1), a = 9.463 (2), b = 11.251 (3), c = 18.871 (6) A, V = 2009.2 (9) A3, Z = 4, Dx = 1.32 g cm-3 (178 K), lambda(Mo K alpha) = 0.7107 A, mu = 0.8762 cm-1, F(000) = 848, T = 178 K, R = 0.0536 for 1673 reflections [Fo > or = 6 sigma (Fo)]. Molecules are hydrogen bonded along the 2(1)-screw axis parallel to a. The hydrogen-bond geometric parameters for N12-H12...O19 (related by 0.5 + x, 1.5 - y, 1 - z) are N...O 2.986 (6), H...O 2.30 (5) A, N-H...O 161 (5) degrees. The C and D rings are trans fused with ring-junction torsion angles of -39.6 (5) and 63.8 (5) degrees for C12a-C12b-N5-C6 and C1-C12b-N5-C4, respectively. The conformation of the C ring is half chair with N5 and C6 -0.168 (4) and 0.552 (5) A, respectively, out of the plane defined by the remaining four atoms of the ring. The D ring is in the chair conformation.

Synthesis of a yohimbine-agarose matrix useful for large-scale and micropurification of multiple alpha 2-receptor subtypes

We have provided a detailed protocol for the synthesis of a yohimbine-agarose matrix that has been shown to be effective for isolation of the alpha 2A-adrenergic receptor from human platelet and purification of the alpha 2A-adrenergic receptor to apparent homogeneity from porcine brain cortex using chromatography on only two sequential yohimbine-agarose columns. In addition, this affinity matrix also interacts with alpha 2 receptors of the alpha 2B subtype extracted from cultured NG108-15 cells. Finally, this affinity matrix has proven useful for monitoring posttranslational modifications of the receptor in digitonin extracts of metabolically labeled cells. Thus, this affinity matrix can be exploited for the purification of multiple alpha 2-adrenergic receptor subtypes on both a macro- and microscale and should be of value to any laboratory exploring the molecular basis for alpha 2-adrenergic functions.

Effects of four non-cholinergic cognitive enhancers in comparison with tacrine and galanthamine on scopolamine-induced amnesia in rats

Amnesia can be induced in rats in the passive avoidance paradigm by administration of scopolamine, a central muscarinic receptor antagonist. Tacrine or galanthamine, inhibitors of acetylcholinesterase, given in conjunction with scopolamine partially reversed the scopolamine-induced deficit in passive avoidance performance. Four so-called cognitive enhancers, all widely used for the treatment of the symptoms associated with mental aging, cerebral insufficiency and senile memory disorder, were investigated in this paradigm. Piracetam, an extract of Ginkgo biloba, dihydroergocristine and a combination of raubasine with dihydroergocristine, all attenuated the amnesia induced by scopolamine. In contrast, nicergoline had no significant effect. Raubasine alone also failed to significantly attenuate scopolamine-induced amnesia, although some doses of raubasine had a non-significant tendency (P less than 0.10) to reduce the amnesia.

Structure of a key intermediate in the synthesis of (-)-5-carboxytetrahydroalstonine and (-)-tetrahydroalstonine

Methyl [4aS*-(4 alpha,4a beta,7 beta,13b beta,14a beta)]-7,8,13,13b,14,14a- hexahydro-4-methyl-5-oxo-4H-indolo-[2,3-a]pyrano[3,4-g]qu inolizine-7-carboxylate acetone solvate, C22H22N2O4.C3H6O, Mr = 424.50, triclinic, P1, a = 9.9955(13), b = 10.8523(14), c = 11.9352(14) A, alpha = 63.189(9), beta = 72.286(9), gamma = 72.901(10) degrees, V = 1081.8(2) A3, Z = 2, Dx = 1.30 g cm-3(198K), mu = 0.8554 cm-1, Mo K alpha radiation, lambda = 0.7107 A, F(000) = 452, T = 198 K, R = 0.0435 for 3842 reflections, FO greater than or equal to 4 sigma (FO). The acetone solvent is hydrogen bonded to the indole NH group with relevant parameters: N13...O1A 2.982(2), H13...O1A 2.10(2) A, N--H...O 164(2) degrees. The conformation at the C and D ring junction is quasi-cis [relevant torsion angles are C7--N6--C13B--C13A 9.4(2) degrees and C5--N6--C13B--C14 46.7(2) degrees] while the conformation at the D and E ring junction is cis [relevant torsion angles are 37.8(2) degrees for C5--C4A--C14A--C14 and 41.3(2) degrees for C4--C4A--C14A--C1].

Genotoxic, mutagenic and recombinogenic effects of rauwolfia alkaloids

In the last decade, the possible correlation between the use of reserpine and rauwolfia drugs as antihypertensive agents and breast cancer incidence has been investigated. For the purpose of evaluating the mutagenic and genotoxic effects of these drugs, reserpine and ajmalicine were studied using the SOS Chromotest and the induction of gene conversion, crossing-over and reverse mutation in the yeast diploid strain XS2316. The results indicated a lack of genotoxic, mutagenic and recombinogenic effects.

Almitrine-raubasine and cognitive impairment in the elderly: results of a 6-month controlled multicenter study

Two-hundred four patients between 70 and 85 years of age were included in a double-blind randomized controlled multicenter study (almitrine-raubasine/placebo). Inclusion criteria were a complaint of cognitive disorders and an objective cognitive impairment evaluated by Folstein et al. "Mini-Mental State" (MMS) and by Sandoz Clinical Assessment for Geriatrics (SCAG). Patients were treated for 6 months and evaluations were performed at the beginning of the trial (T0), then 3 (T3) and 6 (T6) months later. Evaluations included a visual analogic self-rating scale and the following psychometric tests: Trail Making A (TMA), Shopping List Task, Word Fluency, Crossing Out Letters, Logical Memory, Digit Span, and Visual Retention. Anxiety and Depression Scales were also used to assess the effects of almitrine-raubasine on affective status. Statistical analysis involving the whole sample did not show any significant difference between the almitrine-raubasine and placebo groups concerning changes in assessment criteria from T0 to T6. However, these results may have been due to the wide heterogeneity of baseline performances in psychometric tests. To prevent this possible bias, further statistical analysis was performed for each psychometric test after patients had been divided into three classes according to baseline score levels. Considering scores on TMA and Digit Span for patients with scores in the intermediate class on TMA, almitrine-raubasine induced a significantly higher improvement in performance from T0 to T6 than that induced by placebo. On the other hand, no side effects were noted with almitrine-raubasine when compared with placebo. These data suggest that almitrine-raubasine enhances concentrated attention in patients with mild to moderate impairment of this function.

Progress in understanding the pathophysiology of cerebral ischemia: the almitrine-raubasine approach

Cerebral ischemia occurs frequently and is disabling. In addition to preventing and correcting risks factors, drugs prevent cell death induced by ischemia-hypoxia. Precise knowledge of the pathophysiology of cerebral ischemia is the prerequisite for drug development, and the main proofs of efficiency are histopathological and clinical (i.e., the results of controlled studies). Different animal models are considered valid for global, focal, or multifocal ischemia. These models have enabled the identification of deleterious phenomena that could be corrected or neutralized by drugs: hypoxia, lactic acidosis, release of neurotransmitters, influx of calcium, activation of phospholipase A2, release of excitatory amino acids, excess of free radicals, and neuronal cell metabolic paralysis (decrease of oxygen and glucose consumption). The chronology of these events clearly described herein will prompt the choice of the best drug, based on the delay between the ischemic event and the decision to treat. The main pharmacological effects required are the following: antagonism of hypoperfusion, oxygenation improvement, blockade of calcium influx and neurotransmitters action, reduction of acidosis and potassium efflux, blockade of arachidonic cascade and free radicals production, and antiedematous effect. The analysis of almitrine-raubasine (Duxil) pharmacological properties will be used as an example of these potentially anti-ischemic drugs. Almitrine-raubasine pharmacological studies indicate that this drug has several beneficial effects on cerebral ischemic processes. These studies have dealt with effects of hypobaric hypoxia on deoxyglucose uptake in the rat, protective effects on permanent or temporary cerebral ischemia-induced neurobehavioral problems in the gerbil, and preservation of the glycogen content and of the swelling in astrocytes after bilateral occlusion of the carotid arteries in the rabbit.

Efficacy of almitrine-raubasine in cognitive disorders of aging: a double-blind, placebo-controlled, clinical and psychometric study

Early treatment of age-related cognitive impairment can be decisive in enabling elderly patients to remain at home. A double-blind, placebo-controlled trial of almitrine-raubasine was conducted in 40 elderly outpatients (25 women, 15 men; mean age: 73.5 years) with moderate cognitive impairment randomized into two groups, one receiving almitrine and raubasine, the other placebo, two tablets daily for 90 days. They were assessed at T0, T45 and T90 days, using the Toulouse-Pieron test, 8 subtests from the Wechsler Adult Intelligence Scale (WAIS) and the Sandoz Clinical Assessment for Geriatrics (SCAG). End-of-study results were significantly better in the almitrine-raubasine group in all tests: Toulouse-Pieron test (p less than 0.001), WAIS (p less than 0.001), and SCAG (p less than 0.001).

Role of synaptosomal enzymatic alterations and drug treatment in brain aging

The activity patterns of enzyme linked to energy transduction are measured as an estimate of the energy potential capacity of the brain during aging. Early investigations provided information on age-related modifications in the apparent activity of these enzymes in the brain as a whole without taking into account the anatomical, morphological, and functional heterogeneity of the discrete brain regions, the metabolic compartments, and their different time course of aging processes. These considerations prompted the investigators to focus their efforts on subcellular organelles, representative of metabolic compartments, isolated from selected brain regions. In the present study, to better elucidate the role of the synaptic compartment during aging, the maximum rate (Vmax) of enzymes involved in energy metabolic pathways is evaluated in synaptosomes isolated from the cerebral cortex of rats aged 4, 12, and 24 months. The potential catalytic activity of phosphofructokinase and citrate synthase is not affected by aging. In contrast, the Vmax of pyruvate dehydrogenase and particularly of cytochrome oxidase decreases in aged rats. A marked increase is found in the Vmax of glucose-6-phosphate dehydrogenase in 24-month-old rats and could support the availability of nicotinamide adenine dinucleotide phosphate (NADPH) for antiperoxidative processes. Pretreatments of the animals with certain drugs are performed in order to check the responsiveness of the tissue and the plasticity of enzyme proteins during aging. Papaverine (acting on macrocirculation) is ineffective, but raubasine (acting on microcirculation and metabolism) and almitrine (acting on oxygen availability) both interfere with the potential activity of some of the enzymes tested. Their influence differs with the age of the animal and are in agreement with their action on brain carbohydrate and phospholipid metabolism.

Long-term effects and safety of almitrine-raubasine in age-associated cognitive decline

Twenty elderly patients (8 men, 12 women, mean age 67.5 years, range 59-74 years) with age-associated cognitive decline (memory impairment, slowing of thought and inability to concentrate, mean Mini Mental State score 22.0, range 18-24) were included by their general practitioners in an open study of the efficacy and safety of long-term combination therapy with almitrine and raubasine. After a 2-week washout period, patients received almitrine-raubasine for 13 months. Efficacy was evaluated at 2-month intervals using two well-being scales (visual analog and psychoaffective profile) and two behavioral scales (Widlocher's scale, and a scale derived from the Sandoz Clinical Assessment Geriatric scale). Memory was assessed every 6 months. Safety was evaluated by full medical examination and routine laboratory parameters at 2- and 6-month intervals, respectively. On treatment, scores on all scales improved significantly (two-way analysis of variance) throughout the study, as did scores in the two objective memory tests (Friedman test). Safety was demonstrated by the lack of any changes in clinical or laboratory parameters outside the normal range.

Metabolic and circulatory evaluation of cerebral ischemic accident in humans by positron emission tomography: a pilot study with almitrine-raubasine

Positron emission tomography and oxygen-15 were used to evaluate the effect of almitrine-raubasine combination on cerebral blood flow and oxidative metabolism in patients with cerebral ischemia. In five patients aged between 58 and 74 years, with a cerebral ischemic accident in the territory of the middle cerebral artery, blood flow rate, oxygen metabolic rate, and cerebral oxygen extraction were measured before and after a 90-min intravenous perfusion of almitrine bismesilate 15 mg and raubasine 5 mg. Investigations were performed from day 2 to day 7 after stroke occurred. One patient showed evidence of initial relative luxury perfusion, the degree of which was reduced by such combined treatment. The other four patients had a focal reduction in cerebral blood flow and oxygen consumption prior to treatment. The statistical analysis of three cerebral areas (epicenter of lesion, anterior and posterior juxtalesional areas, and homologous heterolateral areas) showed a 3.6% increase in oxygen metabolic rate at the epicenter, when both hemispheres were taken together, and a significant increase in cerebral blood flow in all three areas (3% on the healthy hemisphere, 13% on the injured hemisphere). These changes were greater in some patients than in others. This suggests that heterogeneity of drug responses may correspond to the heterogeneity of the initial status.