UHPLC-MS/MS method for analysis of sobuzoxane, its active form ICRF-154 and metabolite EDTA-diamide and its application to bioactivation study.

Sobuzoxane (MST-16) is an approved anticancer agent, a pro-drug of bisdioxopiperazine analog ICRF-154. Due to the structural similarity of ICRF-154 to dexrazoxane (ICRF-187), MST-16 deserves attention as a cardioprotective drug. This study presents for the first time UHPLC-MS/MS assay of MST-16, ICRF-154 and its metabolite (EDTA-diamide) in cell culture medium, buffer, plasma and cardiac cells and provides data on MST-16 bioactivation under conditions relevant to investigation of cardioprotection of this drug. The analysis of these compounds that differ considerably in their lipophilicity was achieved on the Zorbax SB-Aq column using a mixture of aqueous ammonium formate and methanol as a mobile phase. The biological samples were either diluted or precipitated with methanol, which was followed by acidification for the assay of MST-16. The method was validated for determination of all compounds in the biological materials. The application of the method for analysis of samples from in vitro experiments provided important findings, namely, that (1) MST-16 is quickly decomposed in biological environments, (2) the cardiac cells actively metabolize MST-16, and (3) MST-16 readily penetrates into the cardiac cells and is converted into ICRF-154 and EDTA-diamide. These data are useful for the in-depth examination of the cardioprotective potential of this drug.

Novel SPME fibers based on a plastic support for determination of plasma protein binding of thiosemicarbazone metal chelators: a case example of DpC, an anti-cancer drug that entered clinical trials.

Solid-phase microextraction (SPME) is an alternative method to dialysis and ultrafiltration for the determination of plasma protein binding (PPB) of drugs. It is particularly advantageous for complicated analytes where standard methods are not applicable. Di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) is a lead compound of novel thiosemicarbazone anti-cancer drugs, which entered clinical trials in 2016. However, this agent exhibited non-specific binding on filtration membranes and had intrinsic chelation activity, which precluded standard PPB methods. In this study, using a simple and fast procedure, we prepared novel SPME fibers for extraction of DpC based on a metal-free, silicon string support, covered with C18 sorbent. Reproducibility of the preparation process was demonstrated by the percent relative standard deviation (RSD) of ≤ 9.2% of the amount of DpC extracted from PBS by several independently prepared fibers. The SPME procedure was optimized by evaluating extraction and desorption time profiles. Suitability of the optimized protocol was verified by examining reproducibility, linearity, and recovery of DpC extracted from PBS or plasma. All samples extracted by SPME were analyzed using an optimized and validated UHPLC-MS/MS method. The developed procedure was applied to the in vitro determination of PPB of DpC at two clinically relevant concentrations (500 and 1000 ng/mL). These studies showed that DpC is highly bound to plasma proteins (PPB ≥ 88%) and this did not differ significantly between both concentrations tested. This investigation provides novel data in the applicability of SPME for the determination of PPB of chelators, as well as useful information for the clinical development of DpC. Graphical abstract.

2,6-Dihydroxybenzaldehyde Analogues of the Iron Chelator Salicylaldehyde Isonicotinoyl Hydrazone: Increased Hydrolytic Stability and Cytoprotective Activity against Oxidative Stress.

Salicylaldehyde isonicotinoyl hydrazone (SIH) is a small molecule and lipophilic chelating agent that firmly binds ferric ions from the cellular labile iron pool and is able to protect various tissues against oxidative damage. Previously, SIH possessed the best ratio of cytoprotective efficiency to toxicity among various iron chelators, including the desferrioxamine, deferiprone, and deferasirox used in clinical practice. Here, we prepared a series of 2,6-dihydroxybenzaldehyde aroylhydrazones as SIH analogues with an additional hydroxyl group that can be involved in the chelation of metal ions. Compound JK-31 (2,6-dihydroxybenzaldehyde 4-chlorobenzohydrazone) showed the best cytoprotective efficiency among the studied compounds including SIH. This compound significantly protected H9c2 cardiomyoblast cells against oxidative stress induced by various pro-oxidants, such as hydrogen peroxide, tert-butyl hydroperoxide, paraquat, epinephrine, N-acetyl- p-benzoquinone imine (a toxic metabolite of paracetamol), and 6-hydroxydopamine. The exceptional cytoprotective activity of JK-31 was confirmed using epifluorescence microscopy, where JK-31-treated H9c2 cells maintained a higher mitochondrial inner membrane potential in the presence of a lethal dose of hydrogen peroxide than was observed with cells treated with SIH. Hence, this study demonstrates the deleterious role of free iron ions in oxidative injury and the potential of 2,6-dihydroxybenzaldehyde aroylhydrazones in the prevention of various types of cardiac injuries, highlighting the need for further investigations into these compounds.

Are cardioprotective effects of NO-releasing drug molsidomine translatable to chronic anthracycline cardiotoxicity settings?

Chronic anthracycline (ANT) cardiotoxicity is a serious complication of cancer chemotherapy. Molsidomine, a NO-releasing drug, has been found cardioprotective in different models of I/R injury and recently in acute high-dose ANT cardiotoxicity. Hence, we examined whether its cardioprotective effects are translatable to chronic ANT cardiotoxicity settings without induction of nitrosative stress and interference with antiproliferative action of ANTs. The effects of molsidomine (0.025 and 0.5mg/kg, i.v.) were studied on the well-established model of chronic ANT cardiotoxicity in rabbits (daunorubicin/DAU/3mg/kg/week for 10 weeks). Molsidomine was unable to significantly attenuate mortality, development of heart failure and morphological damage induced by DAU. Molsidomine did not alter DAU-induced myocardial lipoperoxidation, MnSOD down-regulation, up-regulation of HO-1, IL-6, and molecular markers of cardiac remodeling. Although molsidomine increased 3-nitrotyrosine in the myocardium, this event had no impact on cardiotoxicity development. Using H9c2 myoblasts and isolated cardiomyocytes, it was found that SIN-1 (an active metabolite of molsidomine) induces significant protection against ANT toxicity, but only at high concentrations. In leukemic HL-60 cells, SIN-1 initially augmented ANT cytotoxicity (in low and clinically achievable concentrations), but it protected these cells against ANT in the high concentrations. UHPLC-MS/MS investigation demonstrated that the loss of ANT cytotoxicity after co-incubation of the cells in vitro with high concentrations of SIN-1 is caused by unexpected chemical depletion of DAU molecule. The present study demonstrates that cardioprotective effects of molsidomine are not translatable to clinically relevant chronic form of ANT cardiotoxicity. The augmentation of antineoplastic effects of ANT in low (nM) concentrations may deserve further study.

Systematic investigation of phthalocyanines, naphthalocyanines, and their aza-analogues. Effect of the isosteric aza-replacement in the core.

A series of zinc complexes of phthalocyanine, naphthalocyanine and their aza-analogues with alkylsulfanyl substituents was synthesized and characterized by UV-vis and MCD spectroscopy, and their redox properties were investigated using CV, DPV, and SWV approaches as well as spectroelectrochemical methods. Aggregation, photostability, singlet oxygen production, and fluorescence quantum yields of the target complexes were studied as a function of the stepwise substitution of the aromatic C-H fragments by nitrogen atoms. The electronic structure and vertical excitation energies of the target compounds were probed by DFT-PCM and TDDFT-PCM approaches. Introduction of additional nitrogens into the structure leads to a hypsochromic shift of the Q-band and makes the macrocycle strongly electron deficient and more photostable. The impact on the photophysics is limited. The relationships between the type of macrocycle and the studied properties were defined.