Levodopa Concentrations Research Articles

Sequential injection spectrophotometric system for evaluation of mushroom tyrosinase-inhibitory activity

A sequential injection (SI) spectrophotometric method with absorbance detection at 475nm has been developed for evaluating activity of some compounds on an inhibition of the mushroom tyrosinase. The method involved a reaction of 3,4-dihydroxyphenylalanine (l-DOPA) and mushroom tyrosinase to form the o-dopaquinone. The decrease of the o-dopaquinone was related to an increase of tyrosinase-inhibitory activity. Under the optimum conditions (concentration and volume of l-DOPA and mushroom tyrosinase of 2.0mM, 60μL and 142UmL−1, 15μL, respectively), some antioxidant compounds were examined for the tyrosinase-inhibitory activity. A batch enzymatic assay of tyrosinase-inhibitory activity was applied as the reference method for comparison. The results of IC50 values obtained from the proposed method and the batch method were correlated well, with r2 of 0.969. The SIA provides higher precision and degrees of automation, consumes smaller amounts of chemicals and it is simpler and faster than the batch method.

Electrochemical investigation of L-dopa and simultaneous resolution in the presence of uric acid and ascorbic acid at a poly (methyl orange) film coated electrode: A voltammetric study

A poly (methyl orange) (PMO) film on the surface of carbon paste electrode (CPE) was synthesized by electrochemical process and was used for the sensitive and selective determination of L-dopa by employing voltammetric techniques. The electrocatalytic response of the synthesized film coated electrode was found to exhibit excellent activity. The simultaneous determination of L-dopa in the presence of high concentrations of Ascorbic acid (AA) and Uric acid (UA) was found to exhibit very good response at polymer film coated electrode. The effect of pH, scan rate, accumulation time and concentration of L-dopa was studied at developed polymer film modified electrode. The PMOCPE exhibited an efficient electron mediating behaviour together with well resolved peaks for L-dopa, AA, and UA in 0.1M phosphate buffer (PBS) solution of pH 5.0. The anodic peak current showed a linear relation of L-dopa with correlation coefficient of 0.9918 and detection limit 3.7μM and quantification limit 12.37μM respectively. The results showed a good sensitivity and selectivity and high reproducibility of synthesized polymer electrode. The developed method was applied for the determination of L-dopa in pharmaceutical formulations with satisfactory results. The interfacial electron transfer behaviour of L-dopa was studied by electron impedance spectroscopy (EIS), the studies showed that the charge transfer rate was enhanced at PMOCPE when compared with bare CPE.

Frequent administration of levodopa/carbidopa microtablets vs levodopa/carbidopa/entacapone in healthy volunteers

An oral dispersible microtablet formulation of levodopa/carbidopa 5/1.25 mg (LC-5) was developed for individualized repeated dosing. The aim was to compare pharmacokinetic profiles of LC-5 and levodopa/carbidopa/entacapone (LCE). A randomized, crossover study was carried out in 11 healthy subjects. Plasma concentrations of levodopa, carbidopa and 3-O-methyldopa were determined after intake of 300 mg levodopa during the day, either as three intakes of 100/25/200 mg LCE or as a morning dose of 75/18.25 mg followed by five repeated doses of 45/11.25 mg LC-5. Repeated dosing (2.4-hourly) with LC-5 microtablets compared to LCE (6-hourly) avoided long periods with low plasma levodopa levels. Time to maximum plasma concentrations was significantly shorter for LC-5. LC-5 showed lower fluctuation index (FI) in plasma compared to LCE (ANOVA P = 0.0028). FI for dose 2-5 was on average 1.26 for levodopa in LC-5, and 2.23 for dose 1-2 of LCE. The ratio between the two mean FI:s is 0.565; that is, LC-5 gave nearly half the FI as compared to LCE. Fractionation of levodopa with LC-5 into small, frequent administrations as compared to standard administrations of LCE decreased the FI in plasma for both levodopa and carbidopa by nearly half.

Silver Nanoparticles Enhanced Luminescence of Terbium Complex in Solution for L-Dopa Determination

Luminescent properties of a terbium (Tb3+)-L-3, 4-dihydroxyphenylalanine (L-dopa) complex by binding to colloidal silver nanoparticles (Ag NPs) have been presented. Luminescence intensity of the L-dopa complex was dramatically enhanced about 6-7 times by introducing Ag NPs. The Ag NPs concentration on the luminescent intensity was regarded as a main factor that balancing between an enhancing and a quenching effect of the Ag NPs. It was observed that changing the concentration of L-dopa causes the change in luminescence intensity. Under the optimized condition, the luminescence intensity of the system was linearly related to the concentration of L-dopa. Based on this observation, L-dopa-Tb3+ complex containing Ag NPs has been applied for the determination of L-dopa in pharmaceutical formulation. Linear responses of luminescence intensity were observed in the concentration range of 0.25 to 1.5 nM (r = 0.9934) of L-dopa with limit of detection 0.042 nM. The performance of the system was tested using 1.0 x 10(-9) M of L-dopa, yielding a precision of 1.21% RSD for nine replicate measurements. The present method has been successfully applied to determine L-dopa in pharmaceutical samples.

Pharmacokinetics of Levodopa/Carbidopa Delivered From Gastric‐Retentive Extended‐Release Formulations in Patients With Parkinson's Disease

The investigators conducted a single-dose pharmacokinetic (PK) study of levodopa/carbidopa delivered from novel gastric-retentive extended-release (ER) tablets versus a comparator ER tablet (M-ER) in patients with Parkinson's disease. Two levodopa/carbidopa (200 mg/50 mg) gastric-retentive ER formulations (4 hours and 6 hours) and M-ER were administered orally with food. Blood samples were collected for up to 24 hours post dose to determine levodopa and carbidopa concentrations. Tolerability was assessed by monitoring adverse events and measuring vital signs. PK modeling was conducted to estimate the release characteristics for future gastric-retentive ER formulations to achieve a less fluctuating plasma concentration profiles. Compared with M-ER, both gastric-retentive ER formulations exhibited a longer time to reach a lower maximal plasma concentration for levodopa and carbidopa. The 4-hour formulation demonstrated a similar area under the concentration-time curve compared with M-ER, whereas the 6-hour formulation demonstrated a lower area under the concentration-time curve. All formulations were well tolerated. Modeling suggests that a gastric-retentive ER formulation with a longer release duration administered twice daily may achieve a less fluctuating levodopa concentration profile than M-ER administered 3 times daily. This study demonstrates that gastric-retentive ER dosage forms may reduce dose frequency while minimizing the plasma peak-to-trough fluctuation and consequently reduce motor fluctuation in patients with Parkinson's disease.

Coadministration of Domperidone Increases Plasma Levodopa Concentration in Patients With Parkinson Disease

The aim of this study was to examine the effects of the peripheral dopamine D2-receptor antagonist, domperidone, on the plasma kinetics of levodopa in patients with Parkinson disease (PD). In a randomized crossover design, 18 hospitalized patients with PD received a single dose of levodopa/benserazide, 100/25 mg, with or without domperidone, 10 mg, under fasting conditions. Plasma levodopa concentrations were determined up to 3 hours after dose administration. Mean ± SEM levodopa maximum plasma concentration (Cmax) (14.1 ± 2.9 vs 9.7 ± 1.6 μmol/L; P < 0.01), plasma concentration at 30 min (C30 min) (13.7 ± 3.0 vs 8.1 ± 2.0 μmol/L; P < 0.01), and area under the plasma concentration-time curve from 0 to 3 hours (AUC0-3 hr) (15.9 ± 3.1 vs 12.1 ± 2.4 μmol/L · hour; P < 0.05) were significantly higher after coadministration of levodopa with domperidone compared to levodopa alone. Thus, domperidone increased levodopa Cmax and AUC0-3 hr by 1.5- and 1.3-fold, respectively. There were no exacerbations of PD by concomitant domperidone administration. The results demonstrate that coadministration of domperidone increased the bioavailability of levodopa. This may be the reason for no exacerbation of PD in concomitant administration of domperidone, a dopamine D2-receptor blocker.

L-DOPA pharmacokinetics in the MPTP-lesioned macaque model of Parkinson's disease

ObjectiveThe 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned non-human primate is widely used to model Parkinson's disease (PD) and to evaluate the efficacy of new therapies. However, some doubts have been raised about the translatability of findings in the MPTP-lesioned monkey, because the doses of l-3,4-dihydroxyphenylalanine (l-DOPA) required to alleviate parkinsonism and elicit dyskinesia are high, on a mg/kg basis, when compared to clinical practice. Thus, in the MPTP-lesioned macaque, doses ranging from 20 to 40 mg/kg might be used, while in the clinic single l-DOPA administrations ranging from 100 to 200 mg are more typical. However, bioavailability of drugs varies between species and it is unknown how plasma l-DOPA levels providing therapeutic benefit in the non-human primate compare to those having similar actions in PD patients. MethodsWe administered acute challenges of l-DOPA 30 mg/kg orally to MPTP-lesioned macaques with established dyskinesia, and determined plasma, brain and cerebrospinal fluid (CSF) levels of l-DOPA using high-performance liquid chromatography–mass spectrometry/mass spectrometry. ResultsThe maximal plasma concentration of l-DOPA (Cmax) was 18.2 ± 3.8 nmol/ml and was achieved 1.6 ± 0.3 h after administration (tmax). Half-life was 58.8 ± 22.7 min. l-DOPA levels in the caudate nucleus at peak behavioural effect were 3.3 ± 0.7 μg/g tissue protein while they were 1.5 ± 0.1 nmol/ml in the CSF. ConclusionsAlthough therapeutically-active doses of l-DOPA administered to the MPTP-lesioned macaque are higher on a mg/kg basis than those administered in clinical settings, they lead to l-DOPA Cmax similar to those achieved with 200 mg l-DOPA in clinic. l-DOPA tmax and half-life are also similar to those reported in human.

Extraction of Mucuna seed oil using supercritical carbon dioxide to increase the concentration of l-Dopa in the defatted meal

The main aim of this investigation was to extract oil from seeds of Mucuna in order to increase the concentration of l-Dopa in the defatted Mucuna meal. Three different varieties of Mucuna (aterrima, cinerium, deeringiana) and solvents (supercritical carbon dioxide, dichloromethane, hexane) were used. The experiments under supercritical CO2 conditions were performed in a laboratory scale unit at 40 and 60°C over the pressure range from 150 to 250bar. A constant flow rate of CO2 close to 3mL/min was always kept. The results revealed that temperature, pressure and density were important variables for CO2 extraction. The concentration of l-Dopa in the defatted meal from supercritical fluid extraction was always higher than those without oil extraction or extracted using organic solvents. Quantitative and qualitative analyses of the oil extracted under the different investigated experimental conditions shown no significant differences in terms of fatty acid and free glycerol compounds. The same analyses indicated linoleic acid (omega-6) as the major oil component and a content of free fatty acids in the oil extracted with supercritical CO2 close to 5%. The kinetics of oil extraction with CO2 was also investigated at all the considered operating conditions.

Inhibitors of Catechol-O-Methyltransferase

Since the identification of Catechol-O-Methyltransferase (COMT) by Axelrod in 1957, many inhibitors of this enzyme have been reported. While COMT inhibition may be beneficial in a number of disease states, most of the effort over the years has been directed at boosting L-DOPA concentrations as adjunct treatment for Parkinson's disease. This review summarizes the major classes of COMT inhibitors, from early catechol and pyrogallol variants to bisubstrate inhibitors. The nitrocatechol substructure has proven to be a particularly productive scaffold, resulting in two marketed drugs and several improved drug candidates working their way through clinical trials.

Modulation of PC12 Cell Viability by Forskolin-Induced Cyclic AMP Levels Through ERK and JNK Pathways: An Implication for L-DOPA-Induced Cytotoxicity in Nigrostriatal Dopamine Neurons

The intracellular levels of cyclic AMP (cAMP) increase in response to cytotoxic concentrations of L-DOPA in PC12 cells, and forskolin that induces intracellular cAMP levels either protects PC12 cells from L-DOPA-induced cytotoxicity or enhances cytotoxicity in a concentration-dependent manner. This study investigated the effects of cAMP induced by forskolin on cell viability of PC12 cells, relevant to L-DOPA-induced cytotoxicity in Parkinson's disease therapy. The low levels of forskolin (0.01 and 0.1 μM)-induced cAMP increased dopamine biosynthesis and tyrosine hydroxylase (TH) phosphorylation, and induced transient phosphorylation of ERK1/2 within 1 h. However, at the high levels of forskolin (1.0 and 10 μM)-induced cAMP, dopamine biosynthesis and TH phosphorylation did not increase, but rapid differentiation in neurite-like formation was observed with a steady state. The high levels of forskolin-induced cAMP also induced sustained increase in ERK1/2 phosphorylation within 0.25-6 h and then led to apoptosis, which was apparently mediated by JNK1/2 and caspase-3 activation. Multiple treatment of PC12 cells with nontoxic L-DOPA (20 μM) for 4-6 days induced neurite-like formation and decreased intracellular dopamine levels by reducing TH phosphorylation. These results suggest that the low levels of forskolin-induced cAMP increased dopamine biosynthesis in cell survival via transient ERK1/2 phosphorylation. In contrast, the high levels of forskolin-induced cAMP induced differentiation via sustained ERK1/2 phosphorylation and then led to apoptosis. Taken together, the intracellular levels of cAMP play a dual role in cell survival and death through the ERK1/2 and JNK1/2 pathways in PC12 cells.

LC–ESI/MS Analysis of Levodopa and Methyldopa (IS) in Beagle Dog Pharmacokinetic Study after Oral Administration and Domperidone Given in Advance

AbstractA simple, sensitive and accurate method was developed for the quantification of levodopa and methyldopa (IS) in beagle dog plasma by LC–ESI/MS, chromatographic separation was carried out by a Diamonsil C18 column (150 mm × 4.6 mm i.d., 5 mm) with an ODS guard column maintained at 30 °C. The mobile phase was methanol (A) and 0.5% formic acid aqueous solution (B) system in the gradient elution profile, the retention time of levodopa and IS were 4.8 and 6.1 min, respectively, linear range for levodopa concentration was 0.08‐20.0 μg/mL in plasma samples with a correlation coefficient(r) of 0.9978, the limit of detection was 32 ng/mL. CV of intra‐day and inter‐day assays were all less than 15%, mean recoveries of levodopa were all more than 90% in 0.32, 1.6 and 16.0 μg/mL concentrations of levodopa (n = 3). The validated method was successfully applied to the determination of levodopa in plasma samples, pharmacokinetic of levodopa following a single oral dose of compound levodopa tablets and antiemetic drug – domperidone administrated to beagle dogs has been carried out, the main pharmacokinetic parameters of levodopa with domperidone were as follows: Tmax (0.50 ± 0.18) h, Cmax (39.72 ± 7.91) μg/mL, tl/2 (0.65 ± 0.07) h, AUCo‐t (49.01 ± 12.13) μg·h/mL , AUCo‐∞ (49.10 ± 12.16) μg·h/mL, we also evaluated the effect of domperidone on pharmacokinetics of levodopa in beagle dog. We thought non‐oral sustained‐release formulations should be a very good choice instead of this common oral dosage forms on the market, the test results can provide a reference for clinical trials on drug therapy of Parkinson‘s disease.

Pharmacokinetics and Pharmacodynamics of Gastroretentive Delivery of Levodopa/Carbidopa in Patients With Parkinson Disease

To investigate, in patients with Parkinson disease, the pharmacokinetics and pharmacodynamics of levodopa/carbidopa delivered via 3 different extended-release (ER) tablet formulations. This was a randomized, crossover study in patients with stable idiopathic Parkinson disease comparing a conventional ER tablet (C-ER) administered orally 3 times daily with 2 levodopa/carbidopa gastroretentive ER formulations administered orally twice daily, one with an immediate release (IR) component (IR/ER) and one without (ER). Blood samples were collected for pharmacokinetic (PK) analysis, and a finger-tapping test was performed to assess pharmacodynamics. Tolerability was evaluated by monitoring adverse events and measuring vital signs. PK modeling was performed to estimate steady-state levodopa concentrations. Fourteen patients completed the study. Compared with C-ER, both gastroretentive ER tablets significantly extended the first maximum time (6.0 vs 2.5 h; P < 0.025) and had smoother plasma concentration-time profiles while achieving a similar maximum plasma concentration and area under the curve. The IR/ER formulation exhibited a significantly longer duration of concentration above the presumed efficacious threshold of 300 ng/mL (21 vs 18 h; P = 0.0027) compared with C-ER. PK modeling predicts a steady-state levodopa peak/trough ratio of 4 for both IR/ER and ER formulations and a ratio of 21 for C-ER. Furthermore, superior response in the finger tapping test was observed for the IR/ER and ER formulations compared with the C-ER formulation. This study demonstrated that the gastroretentive ER formulations achieved more constant plasma levodopa concentrations and better pharmacodynamics with reduced dose frequency, potentially reducing the on-off phenomena that have been associated with fluctuations in plasma levodopa concentrations.

Citrate-capped Mn-modified CdSe/CdS quantum dots as luminescent probes for levodopa detection in aqueous solution

A novel kind of citrate capped Mn-modified CdSe/CdS quantum dots (QDs) was developed. The Mn-modified CdSe/CdS QDs had a narrow, symmetric emission and strong fluorescence with quantum yield over 41%. The interaction between the QDs and levodopa was investigated. The results showed that levodopa selectively quenched the fluorescence intensity of the QDs. Based on the fluorescence quenching of the synthesized QDs by levodopa, a simple, rapid and specific quantitative method for levodopa was proposed. The factors affecting the fluorescence detection for levodopa were studied. Under the optimum conditions, the quenched intensity of the fluorescence versus levodopa concentration from 1 to 100μM gave a linear response with an excellent correlation coefficient of 0.9996, and the limit of detection (3σ/K) was 2×10−7M. The contents of levodopa in pharmaceutical tablets were determined by the proposed method and the results agreed with the claimed values.

Epinephrine and l-DOPA promote larval settlement and metamorphosis of the tropical oyster, Crassostrea iredalei (Faustino, 1932): An oyster hatchery perspective

The critical and foundation stage of most invertebrates is during the larval settlement and metamorphosis period. Neuroactive compounds at different levels of concentration and exposure time are frequently used as an inducer in the settlement of most bivalve larvae. The larval settlement of the tropical oyster Crassostrea iredalei was investigated by exposing competent larvae to epinephrine (EPI) and l-3,4-dihydroxyphenylalanine (l-DOPA) at five different concentrations (10−3, 10−4, 10−5, 10−6 and 10−7M) for 1 and 24h. The control group consisted of the larvae exposed to 1μm filtered seawater. The optimum yield, 60% of cemented spat, was recorded when larvae were exposed to 10−6M EPI for 1 and 24h. Larvae exposed to all concentrations of l-DOPA yielded lower percentages of cemented spats (<50%) compared to the larvae exposed to EPI. In this study, it was shown that the use of EPI effectively induced cemented spats compared to l-DOPA. After the larvae had cemented onto the substrate, the larvae started to metamorphose. A delay in the larvae settlement caused the mortality of some larvae. The results showed significant differences (p<0.05) between the control and the treatment groups and they provide useful information on the technique of seed production in hatcheries where the chemicals are able to promote the larval settlement and metamorphosis of the larvae of C. iredalei.

Development of a sensor for L-Dopa based on Co(DMG)2ClPy/multi-walled carbon nanotubes composite immobilized on basal plane pyrolytic graphite electrode

L-Dopa is the immediate precursor of the neurotransmitter dopamine, being the most widely prescribed drug in the treatment of Parkinson's disease. A sensitive and selective method is presented for the voltammetric determination of L-Dopa in pharmaceutical formulations using a basal plane pyrolytic graphite (BPPG) electrode modified with chloro(pyridine)bis(dimethylglyoximato)cobalt(III) (Co(DMG)2ClPy) absorbed in a multi-walled carbon nanotube (MWCNT). Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy were used to characterize the materials. The electrocatalytical oxidation of L-Dopa using the Co(DMG)2ClPy/MWCNT/BPPG electrode was investigated by cyclic voltammetry and square wave voltammetry. The parameters that influence the electrode response (the amount of Co(DMG)2ClPy and of MWCNT, buffer solution, buffer concentration, buffer pH, frequency and potential pulse amplitude) were investigated. Voltammetric peak currents showed a linear response for L-Dopa concentration in the range of 3 to 100μM, with a sensitivity of 4.43μAcm−2/μM and a detection limit of 0.86μM. The related standard deviation for 10 determinations of 50μML-Dopa was 1.6%. The results obtained for L-Dopa determination in pharmaceutical formulations (tablets) were in agreement with the compared official method. The sensor was successfully applied for L-Dopa selective determination in pharmaceutical formulations.

Pharmacokinetics of Levodopa/Carbidopa Microtablets Versus Levodopa/Benserazide and Levodopa/Carbidopa in Healthy Volunteers

To compare bioavailability and pharmacokinetics of single doses of 3 different levodopa formulations given orally in healthy volunteers. Two marketed formulations, standard levodopa/carbidopa, 100/25 mg (LC-100), and dispersible levodopa/benserazide, 100/25 mg (LB-100), were used as reference formulations for a newly developed dispersible microtablet formulation of levodopa/carbidopa, 5/1.25 mg (LC-5). The microtablets are intended for individualized dosing of levodopa/carbidopa in Parkinson disease by means of an electronic dose dispenser with a built-in diary for symptom registration. A single-dose, open, randomized, 3-way crossover study was performed in 19 healthy subjects. Concentrations of levodopa, carbidopa, and the metabolite 3-O-MD in plasma were determined after intake of 100 mg of levodopa, that is, one tablet of reference formulations and 20 microtablets of the new formulation. The LC-5 microtablets were bioequivalent to the LC-100 tablets in area under the curve (AUC) and maximum concentration in plasma (Cmax) for levodopa, and to the LB-100 tablets in AUC. The dispersible levodopa/benserazide formulation showed earlier time to Cmax and significantly higher Cmax for levodopa in plasma compared to the microtablets. Carbidopa showed larger interindividual variation in AUC and Cmax than levodopa, and the bioequivalence comparison LC-5/LC-100 for this compound did not reach the target. Nevertheless, comparison of 3-O-MD levels for LC-5/LC-100, assuming proportionality to levodopa levels, demonstrated bioequivalence. The new levodopa/carbidopa microtablets had a pharmacokinetic profile that would allow for a convenient switch of therapy from standard tablets. Frequent dose administration of levodopa/carbidopa microtablets with an electronic dose dispenser might offer an optimal oral drug delivery in Parkinson disease.

Two Decades of Evolving Care with Pump Therapies – What have we Learned?

Since the discovery that the gold standard treatment in Parkinson’s disease (PD), oral levodopa, contributes to motor fluctuations, the treatment strategy of delivering dopaminergic drugs in a continuous manner has been investigated. Motor fluctuations are believed to be the result of a combination of progressive denervation of the striatum with advancing disease and erratic gastric emptying with oral levodopa, which leads to peaks and troughs in plasma levodopa concentration and thus pulsatile stimulation of dopaminergic neurons. Methods have been developed to provide continuous dopaminergic stimulation, such as the delivery of apomorphine by subcutaneous infusion and levodopa/carbidopa by intestinal gel infusion. These therapies have been shown to significantly reduce ‘off’ time and improve motor fluctuations, and therefore have been a major advance in the management of PD.

Enhancement of L-DOPA Production in Micropropagated Plants of two Different Varieties of Mucuna pruriens L., Available in India

Reports on increment in L-DOPA content in micropropagated plants, regenerated through a simple technique following shoot bud multiplication in four strains of two different varieties of Mucuna pruriens are made. Nodal segments from in vitro grown seedlings were cultured on modified MS with various concentrations and combinations of BAP, 2iP, Kn either alone or with NAA. Highest shoot regeneration from the callus was achieved in modified MS fortified with BAP at 1.33 µM level. The regenerated shoots were rooted in vitro in half-strength of liquid MS supplemented with various levels of NAA (0.54 - 10.7 mM) or IBA (0.49 - 9.85 mM). However, roots of superior quality were obtained at 5.4 mM NAA level after two weeks in culture. The regenerants were acclimatized for 2 - 3 weeks and about 85% survival rate was observed after transferring to the field. Both chromosome number stability as well as stability in nuclear DNA contents of the regenerants of all these strains was recorded with complete absence of aneuploidy. The different strains have revealed two to three-folds increase in L-DOPA contents in the cultured plants. The L-DOPA concentration in leaves of the regenerated plants varied from11.85 - 15.42 mg/g dry weight in all these accessions. However, the highest amount was observed in the wild strain of M. pruriens. This is the first report on enhancement of L-DOPA content in differentiated tissue of cultured plants of both the varieties of M. pruriens. Key words: L-DOPA, Micropropagation, Mucuna pruriens, Nuclear DNA D. O. I. 10.3329/ptcb.v21i2.10224 Plant Tissue Cult. &amp; Biotech. 21(2): 115-125, 2011 (December)

Levodopa infusion combined with entacapone or tolcapone in Parkinson disease: a pilot trial

Catechol-O-methyltransferase inhibitors may be used to decrease levodopa requirement. The objective was to investigate whether the levodopa/carbidopa intestinal gel infusion dose can be reduced by 20% without worsening of motor fluctuations and levodopa concentration stability when oral catechol-O-methyltransferase inhibitors are added. A short-term, randomized, partly blinded, crossover, investigator-initiated clinical trial was performed, with levodopa/carbidopa intestinal gel combined with oral entacapone and tolcapone on two different days in 10 patients. The primary outcome measure was difference in coefficient of variation of levodopa in plasma between levodopa/carbidopa, levodopa/carbidopa/entacapone, and levodopa/carbidopa/tolcapone. The secondary outcome measures other pharmacokinetic variables, patient-reported outcome, and blinded analysis of motor performance. Variation of plasma levodopa concentrations did not differ significantly between the treatments. The treatments did not differ regarding motor performance. Levodopa concentrations were significantly higher using tolcapone. Concentrations of the metabolite 3-O-methyldopa decreased gradually during catechol-O-methyltransferase inhibition. According to this small, short-term pilot study, oral catechol-O-methyltransferase inhibitors administered in 5-h intervals may be useful in cases where levodopa/carbidopa intestinal gel dose reduction is wanted. Stability of plasma levodopa levels is not significantly altered, and off-time is not increased when decreasing the levodopa/carbidopa intestinal gel dose by 20%. Rather, the dose should probably be decreased more than 20%, especially under tolcapone co-treatment, to avoid increased dyskinesias with time.

Use of cross-linked tyrosinase aggregates as catalyst for synthesis of l-DOPA

Mushroom tyrosinase immobilized as cross-linked enzyme aggregates (CLEAs) was used as the catalyst for production of l-3,4-dihydroxyphenylalanine (l-DOPA) from l-tyrosine. The synthetic reaction catalyzed by this immobilized enzyme was investigated in different processes. In the batch process, a conversion of 53.0% was obtained during 2h with a productivity of 209.0mgl−1h−1, much superior to other batch processes catalyzed by the same enzyme immobilized with traditional carrier-bound immobilization methods. The effects of pH, temperature, and l-ascorbic acid (as the reducing agent) on the l-DOPA production were examined. Reactions can be tracked by determining the l-DOPA concentration with the spectrophotometric and HPLC methods, both giving consistent results as long as the reducing agent is in sufficient supply. In the continuous synthetic processes carried out in a continuous stirred-tank reactor and a packed bed reactor, a productivity of 103.0 and 48.9mgl−1h−1 was obtained, respectively. The operational stability of the tyrosinase CLEAs can be dramatically improved by entrapment into calcium alginate gels. The CLEA/alginate beads in the continuous stirred-tank reactor achieved a long life time of >104h, producing l-DOPA with a productivity of 57.4mgl−1h−1.