Development and validation of a simple and sensitive method for quantification of levodopa and carbidopa in rat and monkey plasma using derivatization and UPLC–MS/MS

Determination of levodopa by chromatography-based methods in biological samples: a review

Levodopa (L-DOPA) is the most effective drug for Parkinson's disease; however, various side effects occur during therapy. L-DOPA metabolites and the high cumulative dose of L-DOPA were responsible for its side effects. It is necessary to monitor the concentration of L-DOPA and its metabolites for individualized therapy. This review focuses on L-DOPA analysis by chromatography-based methods in biological matrices. Literature published up to September 2021 was collected in the PubMed, Web of Science, and Embase by using search strategy ("levodopa" OR "L-DOPA") AND ("chromatography"). A total of 1249 articles were identified and 32 articles were included. The contents for method development and validation were summarized and analyzed. Due to the instability of catecholamines (L-DOPA, dopamine, and 3-O-methyldopa) and carbidopa, antioxidation (0.5 mg sodium metabisulfite for 100 μL sample) and environment temperature control were used alone or in combination to enhance stability. Sample was mainly pretreated by protein precipitation (0.4-0.7 M perchloric acid). Separation was usually achieved using methanol or acetonitrile:water (with formic acid) on C18 columns. Mass spectrometry, electrochemical detector, ultraviolet-visible detector and fluorescence detector were used for detection. For L-DOPA, the calibration range was 2.5-10,000 ng/mL, the matrix effect and its coefficient of variation was 85-115 and -9.0-8.5%, and the recovery was 66.8-127.0%. Without stabilization strategy, L-DOPA was stable in plasma at room temperature for 1-7 h (4-6 h for most studies), at - 70 °C to - 80 °C for 10-20 days and after 3-5 freeze-thaw cycles. With stabilization strategies, the stability of L-DOPA in plasma was significantly improved. Metabolites of L-DOPA and enzyme inhibitors (carbidopa, entacapone, tolcapone and benserazide) were all stable in biological matrix. This study might be useful for researchers to develop their methods for individualized therapy of patients with Parkinson.

Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) in practice: analysis of drugs and pharmaceutical formulations

Background

UHPLC-MS/MS is connected in various research facilities for the qualitative and quantitative investigation of a pharmaceutical substance, pharmaceutical items, and biological specimen.

Main body

The commence review article is an endeavor to offer pervasive awareness around assorted aspects and details about the UHPLC-MS/MS and related techniques with the aim on practice to an estimation of medicinal active agents in the last 10 years. The article also focused on isolation, separation, and characterization of present impurity in drug and biological samples.

Conclusion

Review article compiles a general overview of medicinally important drugs and their analysis with UHPLC-MS/MS. It gives fundamental thought regarding applications of UHPLC-MS/MS for the study on safety limit. The summary of developed UHPLC-MS/MS methods gives a contribution to the future trend and limitations in this area of research.

The Determination of Parkinson's Drugs in Human Urine by Applying Chemometric Methods

The spectrophotometric-chemometric analysis of levodopa and carbidopa that are used for Parkinson's disease was analyzed without any prior reservation. Parkinson's drugs in the urine sample of a healthy person (never used drugs in his life) were analyzed at the same time spectrophotometrically. The chemometric methods used were partial least squares regression (PLS) and principal component regression (PCR). PLS and PCR were successfully applied as chemometric determination of levodopa and carbidopa in human urine samples. A concentration set including binary mixtures of levodopa and carbidopa in 15 different combinations was randomly prepared in acetate buffer (pH 3.5).). UV spectrophotometry is a relatively inexpensive, reliable, and less time-consuming method. Minitab program was used for absorbance and concentration values. The normalization values for each active substance were good (r2>0.9997). Additionally, experimental data were validated statistically. The results of the analyses of the results revealed high recoveries and low standard deviations. Hence, the results encouraged us to apply the method to drug analysis. The proposed methods are highly sensitive and precise, and therefore they were implemented for the determination of the active substances in the urine sample of a healthy person in triumph.

Monitoring of the deuterated and nondeuterated forms of levodopa and five metabolites in plasma and urine by LC-MS/MS

To compare pharmacokinetics, metabolism and excretion of levodopa and a triply deuterated form, which is being developed as an improved treatment for Parkinson's disease, methods were needed for quantification of the deuterated and nondeuterated forms of levodopa and five metabolites in human plasma and urine. Results: The natural heavy isotopes in the nondeuterated compounds caused an absolute contribution of up to 100% in the response of the deuterated compounds. Similarly, heavy isotopes in the deuterated analytes contributed to the response of the internal standards, but this did not affect the reliability of the results. Conclusion: Deuterated and nondeuterated analytes can be quantified together by LC-MS/MS, but overestimation of the concentrations of the deuterated molecules may be unavoidable and a careful interpretation of the concentration data is essential.

Sensitive LC–MS/MS method for quantitation of levodopa and carbidopa in plasma: application to a pharmacokinetic study

Aim: The combination of levodopa with carbidopa has been used for treatment of Parkinson's disease being an important therapy in dopamine level control in the brain. Both are very polar compounds becoming a challenge for analysis by LC–MS/MS.Materials & methods: In this work, it was developed and validated a sensitive bioanalytical method by UHPLC–MS/MS for simultaneous levodopa and carbidopa quantification in human plasma using a fast protein precipitation method. Moreover, the bioanalytical method was applied to a pharmacokinetic study in healthy volunteers. Results/Conclusion: The results demonstrated a sensitive and adequate method for application to pharmacokinetic/bioequivalence studies.

Novel contribution to the simultaneous monitoring of pramipexole dihydrochloride monohydrate and levodopa as co-administered drugs in human plasma utilizing UPLC-MS/MS

An efficient, selective, sensitive, and rapid ultra-performance liquid chromatography tandem mass spectrometry method was established and validated for the quantification of pramipexole dihydrochloride monohydrate and levodopa simultaneously in human plasma with the aid of diphenhydramine as an internal standard. A simple protein precipitation technique with HPLC grade acetonitrile was efficiently utilized for the cleanup of plasma. The analysis was performed using a Hypersil gold 50 mm × 2.1 mm (1.9 µm) column and a mobile phase of 0.2% formic acid and methanol (90: 10 v/v). The triple-quadrupole mass spectrometer equipped with an electrospray source operated in the positive mode was set up in the selective reaction monitoring mode (SRM) to detect the ion transitions m/z 212.15 →153.01, m/z 198.10→ 135.16, and m/z 255.75 → 166.16 for pramipexole dihydrochloride monohydrate, levodopa, and diphenhydramine, respectively. The method was thoroughly validated according to FDA guidelines and proved to be linear, accurate, and precise over the range 100-4000 pg/mL for pramipexole dihydrochloride monohydrate and 60-4000 ng/mL for levodopa. The proposed method was effectively applied for monitoring both drugs in plasma samples of healthy volunteers.

Potential of Aqueous Two-Phase Systems for the Separation of Levodopa from Similar Biomolecules

BACKGROUND

Levodopa is a precursor of several neurotransmitters, such as dopamine, and is used in the treatment of the Parkinson's disease. In this work, an alternative strategy was studied to separate levodopa from similar biomolecules using aqueous two-phase systems (ATPS).

RESULTS

Ternary ATPS composed of polyethylene glycol (PEG) 400 or ionic liquids (ILs), citrate buffer (K3C6H5O7/C6H8O7) at pH 7.0 and water, and quaternary ATPS composed of PEG 400, K3C6H5O7/C6H8O7 at pH 7.0, water and the same ILs at 5 wt%, were studied. The respective liquid-liquid phase diagrams were determined at 298 K to appraise the mixture compositions required to form two-phase systems, followed by studies of the partition of levodopa and structurally similar biomolecules (dopamine, L-phenylalanine, and L-tyrosine). Their partition coefficients and extraction efficiencies have been determined, and the selectivity of the ATPS to separate levodopa from the remaining biomolecules evaluated.

CONCLUSION

The results obtained indicated that PEG-based ATPS were the most effective to separate levodopa from L-phenylalanine while the separation from the other biomolecules was better using IL-based ATPS, in particular those based on [P4444]Cl and [N4444]Cl, with extraction efficiencies of levodopa to the salt-rich phase ranging between 62.7 and 74.0%, and of the remaining biomolecules to polymer/IL-rich phase up to 91.5%.

Simultaneous estimation of levodopa, carbidopa and 3-oxymethyldopa in rat plasma using HPLC-ECD

The aim of study was to develop a suitable analytical method for simultaneous estimation of levodopa, carbidopa and 3-O-methyl dopa in rat plasma. Chromatographic separation of plasma samples was achieved using a reverse-phase C18 column. The mobile phase used consisted of a mixture of methanol and phosphate buffer (10 mM, pH 3.50) in the ratio of 90:10 v/v. All analytes were estimated by electrochemical detection at +800 mV. The developed method has been validated as per the standard guidelines. Precision study results were found to be satisfactory, with percentage relative standard deviation for repeatability and intermediate precision <3.96 and 6.56%, respectively, for all analytes detected in rat plasma. The developed method in rat plasma was found to be simple, rapid, accurate, precise and specific. The proposed method has been successfully applied for analysis of rat plasma samples obtained during an oral pharmacokinetic study of sustained release pellets of levodopa and carbidopa in rats. Copyright © 2016 John Wiley & Sons, Ltd.

Determination of Picogram Levels of Levodopa in Pharmaceutical Preparations and Biofluids by Flow-Injection Chemiluminescence

An ultrasensitive method for determination of L-dopa at picogram levels by flow-injection chemiluminescence (FI-CL) as presented for the first time, based on the quenching effect of levodopa (L-dopa) on the luminol-lysozyme reaction. It was found that the decrement of CL intensity was linearly proportional to the logarithm of L-dopa concentration ranging from 3.0 to 7.0 × 103pg mL-1(R= 0.9967), with the limit of detection (LOD) of 1.0 pg mL-1(3σ). The proposed procedure was successfully applied to the determination of L-dopa in pharmaceutical preparations, human saliva, serum, and urine samples with the recoveries ranging from 96.7% to 104.3% and RSDs less than 4.0% (n= 5).