Chiral enantiomers of drugs often exhibit distinct pharmacological activities despite their similar physical and chemical properties. Developing efficient methods for their distinguishment is crucial for pharmaceutical quality control. Here, we presented a novel approach using a CTT (Chlorite-Tetramethylammonium Hydroxide-Tetrathionate) clock reaction system for kinetic chiral enantiomer recognition. DOPA enantiomers were selected for this purpose, in which L-DOPA is therapeutic efficacy in treating Parkinson's disease by precursoring dopamine while D-DOPA lacks such a function. By introducing equal amounts of L-DOPA and D-DOPA into the CTT clock system, we observed a more prolonged induction period for L-DOPA compared to D-DOPA, enabling their quick differentiation. Moreover, a linear relationship between the induction period and the concentration (1.190 × 10 −6 mol/L to 4.5238 × 10 −6 mol/L) of L-DOPA or D-DOPA allowed quantitative detection of L-DOPA or D-DOPA samples. This method could also be applied to analyze varying concentration ratios of L-DOPA and D-DOPA mixtures at a fixed total concentration. Study on mechanism indicates that both L-DOPA and D-DOPA react with ClO 2 · radical to finally generate DHICA through oxidation, with their kinetic disparities evident during this process. These kinetic disparities between L-DOPA and D-DOPA oxidation arises from stereospecific hydrogen-bonding interactions in the cyclodopa intermediate. The weaker hydrogen bond in L-DOPA-derived cyclodopa likely facilitates its cleavage during oxidation, thereby accounting for the faster reaction kinetics observed in the clock system compared to D-DOPA. This makes L-DOPA exhibit more fast consumption of chlorine dioxide than D-DOPA, and resulting larger the extension in the induction period with L-DOPA than that with D-DOPA. Such a method coupling CCT clock demonstrates its versatility and potential for broader applications in chiral drug analysis.
Chiral impurity analysis presents significant challenges due to limitations of detection methods. Levodopa (L-Dopa) is the primary medication for Parkinson's disease treatment for over 50 years. However, the detection of its chiral impurity is difficult due to the similarity of polarity. This study presents a novel analytical method for the quantitative detection of trace amount of D-Dopa, as well as other three impurities. The method demonstrated excellent chromatographic resolution for D-Dopa and L-Dopa (resolution = 4.15) and achieved a derivatization efficiency of 97% using a chlorine-labeled chiral probe (D-BPCl) for chemical derivatization, followed by analysis with liquid chromatography-tandem mass spectrometry (LC-MS/MS) on a conventional C18 column. Meanwhile, D-BPCl showed strong chiral selectivity on D-Dopa, and the ratio of mass spectrometric response for labeled D-Dopa to that of L-enantiomers was 2.78-fold under the same condition. The developed method demonstrates high sensitivity with detection limits of 7.88 μ g L -1 for D-Dopa, and 9.85 μ g L -1 for L-Dopa, with good linearity for every analyte (R 2 > 0.99), recoveries ranging from 94.1% to 106.8%, and high repeatability with relative standard deviation (RSD) values predominantly below 5%. Then the method was applied to analyze fifteen batches of levodopa tablets from five manufacturers. D-Dopa was successfully detected with the corresponding content ranging from 0.15% to 0.44%, which suggests that D-Dopa are more likely generated during the production process. The study underscores the significant safety concerns regarding Dopa-containing medications.
危险品化学品经营许可证（带存储）