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

Greenness and whiteness appraisal for bioanalysis of quetiapine, levodopa and carbidopa in spiked human plasma by high performance thin layer chromatography

A sustainable HPTLC-densitometric method was developed for quantitative determination of Quetiapine (QUET), Levodopa (LD) and Carbidopa (CD) in presence of Dopamine (DOP) as an internal standard. This applicable technique was achieved by spiking human plasma and extraction was performed using the protein precipitation approach. The mobile phase used was acetone, dichloromethane, n-butanol, glacial acetic acid and water (3: 2.5: 2: 2: 1.75, by volume). Method validation was done according to US-FDA guidelines and was able to quantify Quetiapine, Levodopa and Carbidopa in the ranges of 100-4000, 200-8000 and 30-1300 ng/mL, respectively. Bioanalytical method validation parameters were assessed for the studied drugs. Finally, the analytical suggested methodology was evaluated using various green and white analytical chemistry metrics and other tools, such as the green solvent selection tool, analytical eco-scale, green analytical procedure index, analytical greenness metric approach and the red-green-blue algorithm tool. The results revealed that the applied analytical method had a minor impact on the environment and is a relatively greener option than other previously reported chromatographic methods.

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.

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.