HPLC study on stability of pyridoxal isonicotinoyl hydrazone

Development and validation of RP-HPLC method for stability evaluation of model hydrazone, containing a pyrrole ring

RP-HPLC method with UV detection was developed and validated for determination of the chemical stability and stability in close to physiological conditions of a model pyrrole hydrazone ethyl 5-(4-bromophenyl)-1-(1-(2-(4-hydroxy-3-methoxybenzylidene) hydrazineyl)-4-methyl-1-oxopentan-2-yl)-2-methyl-1H-pyrrole-3-carboxylate (D_5d), containing susceptible to hydrolysis hydrazone group. The evaluated substance was subjected to the influence of a variety of pH , representing the main physiological values of 37°C and corresponding pH values in the stomach (pH 2.0), blood (pH 7.4) and small intestine (pH 9.0). Chemical stability in a highly alkaline medium with a pH of 13.0 was also evaluated. The hydrazone I tested was found to be stable at pH 7.4 and pH 9.0 and 37 ° C and hydrolyzed under strong acidic (pH 2.0) and highly alkaline media (pH 13.0) and at the same temperature.The products of hydrolysis were identified to be the initial hydrazide and aldehyde, pointing the hydrazone group as most liable.

Investigation on the Stability of New Biologically Active Thiosemicarbazone- Derived Compounds by a Validated HPLC-PDA Method

Background:

New Chemical Entities (NCEs) could be generally exposed to several stress conditions of hydrolysis, oxidation, photolysis and thermal degradation in order to better characterize the compounds and to know if the degradation processes lead to generate undesired (or toxic) products.

Objective:

This paper reports the development and validation of an HPLC-PDA method for the qualiquantitative profiles determination and chemical-physical stability evaluation after forced decomposition studies of thiosemicarbazone-derived compounds endowed with interesting pharmacological activities.

Methods:

All compounds and two possible degradation products were resolved by using a Grace® C-18 (ODS) column (250 mm × 4.6 mm; 5 mm particle size) in gradient elution mode. The chromatographic analysis was run in 28 min. The analytical method was correctly validated using weighted-matrix matched standard curves in the following ranges: 1-100 µg mL-1 for the lead compounds, and 0.1-8 μg mL-1 for the two possible degradation products showing a good correlation coefficients (≥0.9756). Precision and trueness comply with International Guidelines on method validation.

Results:

The obtained results demonstrated an excellent stability of the thiosemicarbazone-derived products following the treatment with UV set at 254 nm and heat (at 80°C). In solution, however, the compounds showed different stability profiles.

Conclusion:

The results obtained through the forced degradation studies provided important information not only for handling, formulation and storage of the substances, but also for the possible chemical changes in order to increase the stability. Given the importance of the non-conventional dosage forms, the stability of the substances was also analyzed in the presence of widely used surfactants.

Thermo-targeted drug delivery of geldanamycin to hyperthermic tumor margins with diblock elastin-based biopolymers

The tumor margins are the barrier to hepatocellular carcinoma (HCC) eradication for tumors>3 cm. Indeed, inadequately treated tumor margins commonly result in local and regional HCC recurrence with increased size and mass. Tumor recurrence is a common problem with chemotherapy, radiotherapy, thermal ablation, and/or surgical resection, by the inability to properly treat the tumor core and the tumor margins. Here we present novel thermosensitive biopolymer-drug conjugates for thermo-targeted chemotherapy at hyperthermic isotherms produced by focal, locoregional thermal ablation. The chemotherapeutic target is heat shock protein 90 (HSP90), a key molecular chaperone of several, and potent pro-oncogenic pathways including Akt, Raf-1, and mutated p53 that is upregulated in HCC. To inhibit HSP90, we have chosen geldanamycin (GA), a potent HSP90 inhibitor. GA has gained significant attention for its low IC50 ~ 1 nM and inhibition of Akt and Raf-1, amongst other critical pro-oncogenic pathways. Despite such evidence, clinical trials of GA have not shown promise due to off-target toxicity and poor formulation design. Here, we propose using diblock elastin-based biopolymers as a Ringsdorf macromolecular GA solubilizer--a new generation containing functional poly(Asp)/(Glu) blocks for facile drug conjugation and an ELP block for thermo-targeting of hyperthermic ablative margins. GA release is controlled by pH-sensitive, covalent hydrazone bonds with the biopolymer backbone to avoid systemic toxicity and off-target effects. The resultant biopolymer-conjugates form stable nanoconstructs and display tunable, acute phase transitions at high temperatures. Drug release kinetics are favorable with or without the presence of serum. Thermo-targeted chemotherapy and synchronous thermal ablation provide a unique opportunity for simultaneous destruction of the HCC ablative margins and tumor core for focal, locoregional control of HCC.

Use of different stationary phases for separation of isoniazid, its metabolites and vitamin B6 forms

The ability of different stationary phases developed for the analysis of polar compounds (ZIC-HILIC, ZIC-pHILIC and Zorbax SB-Aq) to separate isoniazid, its metabolites (acetylisonazid, pyridoxal isonicotinoyl hydrazone, pyridoxal isonicotinoyl hydrazone 5-phosphate), pyridoxine, pyridoxal and pyridoxal 5-phosphate under MS compatible conditions was systematically investigated using HPLC-UV. The mobile phase strength, pH and buffer concentration were modified to assess their impact on the retention of these compounds. The best available separation of the compounds was achieved using 1 mM ammonium formate (pH≈6) and ACN (20:80, v/v) on ZIC-HILIC and employing 5 mM ammonium formate (pH 3.0) and ACN (40:60, v/v) on ZIC-pHILIC. A gradient profile using 0.5 mM ammonium formate (pH≈6) and MeOH (0-12 min: 10% MeOH, 12-15 min: 10-50% MeOH, 15-35 min: 50% MeOH, 35.0-35.2 min: 50-10% MeOH, 35.2-45.0 min: 10% MeOH) provided the best separation of the compounds on Zorbax SB-Aq. Subsequent LC-MS analysis demonstrated that ZIC-HILIC is useful for the analysis of pyridoxine, pyridoxal and pyridoxal isonicotinoyl hydrazone. However, the chromatographic conditions developed for the analysis of the compounds on Zorbax SB-Aq are capable of achieving the best separation of all compounds in this study with the higher sensitivity for most of the analytes.

Synthesis and initial in vitro evaluations of novel antioxidant aroylhydrazone iron chelators with increased stability against plasma hydrolysis

Oxidative stress is known to contribute to a number of cardiovascular pathologies. Free intracellular iron ions participate in the Fenton reaction and therefore substantially contribute to the formation of highly toxic hydroxyl radicals and cellular injury. Earlier work on the intracellular iron chelator salicylaldehyde isonicotinoyl hydrazone (SIH) has demonstrated its considerable promise as an agent to protect the heart against oxidative injury both in vitro and in vivo. However, the major limitation of SIH is represented by its labile hydrazone bond that makes it prone to plasma hydrolysis. Hence, in order to improve the hydrazone bond stability, nine compounds were prepared by a substitution of salicylaldehyde by the respective methyl- and ethylketone with various electron donors or acceptors in the phenyl ring. All the synthesized aroylhydrazones displayed significant iron-chelating activities and eight chelators showed significantly higher stability in rabbit plasma than SIH. Furthermore, some of these chelators were observed to possess higher cytoprotective activities against oxidative injury and/or lower toxicity as compared to SIH. The results of the present study therefore indicate the possible applicability of several of these novel agents in the prevention and/or treatment of cardiovascular disorders with a known (or presumed) role of oxidative stress. In particular, the methylketone HAPI and nitro group-containing NHAPI merit further in vivo investigations.

Control and analysis of hydrazine, hydrazides and hydrazones--genotoxic impurities in active pharmaceutical ingredients (APIs) and drug products

This is the latest of a series of reviews focused on the analysis of genotoxic impurities. This review summarises the analytical approaches reported in the literature relating to hydrazine, hydrazines, hydrazides and hydrazones. It is intended to provide guidance for analysts needing to develop procedures to control such impurities, particularly where this is due to concerns relating to their potential genotoxicity. Of particular note is the wide variety of techniques employed, both chromatographic and spectroscopic, with most involving derivatisation. Such a wide variety of options allow the analyst a real choice in terms of selecting the most appropriate technique specific to their requirements. Several generic methodologies, covering the three main analytical approaches; i.e. HPLC (high performance liquid chromatography), GC (gas chromatography) and IC (ion chromatography), are also described.

Development of an LC-MS/MS method for analysis of interconvertible Z/E isomers of the novel anticancer agent, Bp4eT

This study was focused on a liquid chromatography/tandem mass spectrometry (LC/MS/MS) method development for quantification of a novel potential anticancer agent, 2-benzoylpyridine 4-ethyl-3-thiosemicarbazone (Bp4eT), in aqueous media. Solid Bp4eT was found to consist predominantly of the Z isomer, while in aqueous media, both isomers coexist. Sufficient separation of both isomers was achieved on a Synergi 4u Polar RP column with a mobile phase composed of 2 mM ammonium formate, acetonitrile, and methanol (30:63:7; v/v/v). The photo diode array analysis of both isomers demonstrated different absorption spectra which hindered UV-based quantification. However, an equal and reproducible response was found for both isomers using an MS detector, which enables the determination of the total content of Bp4eT (i.e., both E- and Z- isomeric forms) by summation of the peak areas of both isomers. 2-Hydroxy-1-naphthylaldehyde 4-methyl-3-thiosemicarbazone (N4mT) was selected as the internal standard. Quantification was performed in selective reaction monitoring using the main fragments of [M+H](+) (240 m/z for Bp4eT and 229 m/z for N4mT). The method was validated over 20-600 ng/ml. This procedure was applied to a preformulation study to determine the proper vehicle for parenteral administration. It was found that Bp4eT was poorly soluble in aqueous media. However, the solubility can be effectively improved using pharmaceutical cosolvents. In fact, a 1:1 mixture of PEG 300/0.14 M saline markedly increased solubility and may be a useful drug formulation for intravenous administration. This investigation further accelerates development of novel anticancer thiosemicarbazones. The described methods will be useful for analogs currently under development and suffering the same analytical issue.

Anthracycline-induced cardiotoxicity: overview of studies examining the roles of oxidative stress and free cellular iron

The risk of cardiotoxicity is the most serious drawback to the clinical usefulness of anthracycline antineoplastic antibiotics, which include doxorubicin (adriamycin), daunorubicin or epirubicin. Nevertheless, these compounds remain among the most widely used anticancer drugs. The molecular pathogenesis of anthracycline cardiotoxicity remains highly controversial, although the oxidative stress-based hypothesis involving intramyocardial production of reactive oxygen species (ROS) has gained the widest acceptance. Anthracyclines may promote the formation of ROS through redox cycling of their aglycones as well as their anthracycline-iron complexes. This proposed mechanism has become particularly popular in light of the high cardioprotective efficacy of dexrazoxane (ICRF-187). The mechanism of action of this drug has been attributed to its hydrolytic transformation into the iron-chelating metabolite ADR-925, which may act by displacing iron from anthracycline-iron complexes or by chelating free or loosely bound cellular iron, thus preventing site-specific iron-catalyzed ROS damage. However, during the last decade, calls for the critical reassessment of this "ROS and iron" hypothesis have emerged. Numerous antioxidants, although efficient in cellular or acute animal experiments, have failed to alleviate anthracycline cardiotoxicity in clinically relevant chronic animal models or clinical trials. In addition, studies with chelators that are stronger and more selective for iron than ADR-925 have also yielded negative or, at best, mixed outcomes. Hence, several lines of evidence suggest that mechanisms other than the traditionally emphasized "ROS and iron" hypothesis are involved in anthracycline-induced cardiotoxicity and that these alternative mechanisms may be better bases for designing approaches to achieve efficient and safe cardioprotection.

Development and validation of HPLC-DAD methods for the analysis of two novel iron chelators with potent anti-cancer activity

Di-2-pyridylketone isonicotinoyl hydrazone (PKIH) and di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT) novel iron chelators which possess marked anti-cancer activity in vivo. However, further progress in the development of these drug candidates requires precise and convenient methods for their qualitative and quantitative analysis. The aim of this study was to develop and validate HPLC methods suitable for the purity and stability evaluation of Dp44mT and PKIH and subsequently to employ these methods in stress tests addressing their chemical stability. The chromatographic analyses of both chelators were accomplished via HPLC using a Discovery HSF5 column (25 cm x 4 mm; 5 microm). For separation of Dp44mT and its synthetic precursors, the mobile phase was composed of a mixture of 2 mM EDTA and acetonitrile in a ratio 60:40 (v/v). A desirable separation of PKIH from its synthetic precursors was achieved with a mixture of 0.01 M phosphate buffer (pH 3.0), methanol and acetonitrile in a ratio of 65:21:14 (v/v/v) with the addition of EDTA (2 mM). In order to confirm the utility of these HPLC methods for measuring these drugs and their stability, Dp44mT and PKIH were subjected to chemical stress tests. These experiments showed that Dp44mT was relatively stable against hydrolytic degradation, but quite sensitive to oxidation. On the other hand, PKIH was slightly sensitive to acid-catalyzed hydrolysis, but it was relatively stable under other tested conditions. Furthermore, these studies confirmed the utility of these methods not only for appropriate evaluation of purity but also stability. The analytical methods developed and validated in this study, as well as the basic data on the chemical stability, should further support the development of both these novel anti-cancer chelators as promising drug candidates.