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Liu Y, Xi H, Wang J, Fu J, Shi T. Mechanistic studies on the oxidation reaction of antitubercular drug isoniazid and its analogy hydrazides by chlorine dioxide over a wide pH range. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Antioxidative Reactivity of L-Ascorbic Acid and D-Isoascorbic Acid Species towards Reduction of Hexachloroiridate (IV). J CHEM-NY 2021. [DOI: 10.1155/2021/5505741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The pair [IrCl6]2–/[IrCl6]3– has been demonstrated to be a good redox probe in biological systems while L-ascorbic acid (AA) is one of the most important antioxidants. D-isoascorbic acid (IAA) is an epimer of AA and is widely used as an antioxidant in various foods, beverages, meat, and fisher products. Reductions of [IrCl6]2– by AA and IAA have been analyzed kinetically and mechanistically in this work. The reductions strictly follow overall second-order kinetics and the observed second-order rate constants were collected in the pH region of 0 ≤ pH ≤ 2.33 at 25.0°C. Spectrophotometric titration experiments revealed a well-defined 1 : 2 stoichiometry, namely Δ[AA] : Δ[Ir(IV)] or Δ[IAA] : Δ[Ir(IV)] = 1 : 2, indicating that L-dehydroascorbic acid (DHA) and D-dehydroisoascorbic acid (DHIA) were the oxidation products of AA and IAA, respectively. A reaction mechanism is suggested involving parallel reactions of [IrCl6]2– with three protolysis species of AA/IAA (fully protonated, monoanionic, and dianionic forms) as the rate-determining steps and formation of ascorbic/isoascorbic and ascorbate/isoascorbate radicals; in each of the steps, [IrCl6]2– acquires an electron via an outer-sphere electron transfer mode. Rate constants of the rate-determining steps have been derived or estimated. The fully protonated forms of AA and IAA display virtually identical reactivity whereas ascorbate and isoascorbate monoanions have a significant reactivity difference. The ascorbate and isoascorbate dianions are extremely reactive and their reactions with [IrCl6]2– proceed with the diffusion-controlled rate. The species versus pH and the species reactivity versus pH distribution diagrams were constructed endowing that the ascorbate/isoascorbate monoanionic form dominated the total reactivity at physiological pH. In addition, the value of pKa1 = 3.74 ± 0.05 for IAA at 25.0°C and 1.0 M ionic strength was determined in this work.
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Zhou L, Li T, Sun Y, Tian H, Gao C, Liu C, Kong L, Zhang G, Shi T. Mechanistic scrutiny of the oxidations of thiol‐containing drugs cysteamine and
d
‐penicillamine by
cis
‐diamminetetrachloroplatinum(IV). INT J CHEM KINET 2020. [DOI: 10.1002/kin.21464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Li Zhou
- College of Chemistry, Chemical Engineering and Materials Science Zaozhuang University Zaozhuang Shandong Province 277160 China
| | - Tiejian Li
- National Engineering Technology Center of Chirality Pharmaceuticals Lunan Pharmaceutical Group Co., Ltd. Linyi Shandong Province 276006 China
- Shandong New Time Pharmaceutical Co., Ltd. Feixian Shandong Province 273400 China
| | - Ying Sun
- National Engineering Technology Center of Chirality Pharmaceuticals Lunan Pharmaceutical Group Co., Ltd. Linyi Shandong Province 276006 China
| | - Hongwu Tian
- Shandong New Time Pharmaceutical Co., Ltd. Feixian Shandong Province 273400 China
| | - Cunxiu Gao
- National Engineering Technology Center of Chirality Pharmaceuticals Lunan Pharmaceutical Group Co., Ltd. Linyi Shandong Province 276006 China
| | - Chunli Liu
- College of Chemistry, Chemical Engineering and Materials Science Zaozhuang University Zaozhuang Shandong Province 277160 China
| | - Lingli Kong
- College of Chemistry, Chemical Engineering and Materials Science Zaozhuang University Zaozhuang Shandong Province 277160 China
| | - Guimin Zhang
- National Engineering Technology Center of Chirality Pharmaceuticals Lunan Pharmaceutical Group Co., Ltd. Linyi Shandong Province 276006 China
- Shandong New Time Pharmaceutical Co., Ltd. Feixian Shandong Province 273400 China
| | - Tiesheng Shi
- College of Chemistry, Chemical Engineering and Materials Science Zaozhuang University Zaozhuang Shandong Province 277160 China
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Kinetic Analysis of the Reduction Processes of a Cisplatin Pt(IV) Prodrug by Mesna, Thioglycolic Acid, and Thiolactic Acid. J CHEM-NY 2020. [DOI: 10.1155/2020/5868174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Although Mesna is an FDA-approved chemotherapeutic adjuvant and an antioxidant based largely on its antioxidative properties, kinetic and mechanistic studies of its redox reactions are limited. A kinetic analysis of the reduction processes of cis-diamminetetrachloroplatinum(IV) (cis-[Pt(NH3)2Cl4], a cisplatin Pt(IV) prodrug) by thiol-containing compounds Mesna, thioglycolic acid (TGA), and DL-thiolactic acid (TLA) was carried out in this work at 25.0°C and 1.0 M ionic strength. The reduction processes were followed under pseudo-first-order conditions and were found to strictly obey overall second-order kinetics; the observed second-order rate constant k′ versus pH profiles were established in a wide pH range. A general reaction stoichiometry of Δ[Pt(IV)] : Δ[Thiol]tot = 1 : 2 was revealed for all the thiols; the thiols were oxidized to their corresponding disulfides which were identified by mass spectrometry. Reaction mechanisms are proposed which involves all the prololytic species of the thiols attacking the Pt(IV) prodrug in parallel, designating as the rate-determining steps. Transient species chlorothiol and/or chlorothiolate are formed in these steps; for each particular thiol, these transient species can be trapped rapidly by another thiol molecule which is in excess in the reaction mixture, giving rise to a disulfide as the oxidation product. The rate constants of the rate-determining steps were elucidated, revealing reactivity enhancements of (1.4–8.9) × 105 times when the thiols become thiolates. The species versus pH and reactivity of species versus pH distribution diagrams were constructed, demonstrating that the species ‒SCH2CH2SO3‒ of Mesna largely governs the total reactivity when pH > 5; in contrast, the form of Mesna per se (mainly as HSCH2CH2SO3‒) makes a negligible contribution. In addition, a well-determined dissociation constant for the Mesna thiol group (pKa2 = 8.85 ± 0.05 at 25.0°C and μ = 1.0 M) is offered in this work, which was determined by both kinetic approach and spectrophotometic titration method.
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