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

Examination of diverse iron-chelating agents for the protection of differentiated PC12 cells against oxidative injury induced by 6-hydroxydopamine and dopamine

Labile redox-active iron ions have been implicated in various neurodegenerative disorders, including the Parkinson's disease (PD). Iron chelation has been successfully used in clinical practice to manage iron overload in diseases such as thalassemia major; however, the use of conventional iron chelators in pathological states without systemic iron overload remains at the preclinical investigative level and is complicated by the risk of adverse outcomes due to systemic iron depletion. In this study, we examined three clinically-used chelators, namely, desferrioxamine, deferiprone and deferasirox and compared them with experimental agent salicylaldehyde isonicotinoyl hydrazone (SIH) and its boronate-masked prochelator BSIH for protection of differentiated PC12 cells against the toxicity of catecholamines 6-hydroxydopamine and dopamine and their oxidation products. All the assayed chelating agents were able to significantly reduce the catecholamine toxicity in a dose-dependent manner. Whereas hydrophilic chelator desferrioxamine exerted protection only at high and clinically unachievable concentrations, deferiprone and deferasirox significantly reduced the catecholamine neurotoxicity at concentrations that are within their plasma levels following standard dosage. SIH was the most effective iron chelator to protect the cells with the lowest own toxicity of all the assayed conventional chelators. This favorable feature was even more pronounced in prochelator BSIH that does not chelate iron unless its protective group is cleaved in disease-specific oxidative stress conditions. Hence, this study demonstrated that while iron chelation may have general neuroprotective potential against catecholamine auto-oxidation and toxicity, SIH and BSIH represent promising lead molecules and warrant further studies in more complex animal models.

Development and Validation of a Liquid Chromatographic Method for Aroylhydrazones at Hydrolytic Conditions

Background:

The indole-containing aroylhydrazone derivatives 3a-c with potent antimycobacterial activity against a referent strain M. tuberculosis H37Rv and low cytotoxicity were evaluated for their stability via the precise and accurate HPLC analytical method in aqueous media of different pH (2.0, 7.0, 9.0 and 12.0).

Objective:

The study describes the development and validation of a simple and reliable HPLC-UV procedure for the determination of aroylhydrazone derivatives and their hydrolytic stability. Additionally, to recognize if hydrolysis leads to generating undesired products, the degradation processes were identified.

Method:

The separation was achieved with a LiChrosorb®RP-18 (250 x 4.6 mm) column, at ambient temperature with isocratic mode with mobile phase containing mixture of component A (acetonitrile) and component B (0.001M NaH2PO4, with 5 mM 1-heptane sulfonic acid sodium salt, adjusted to pH 3.0) in a ratio 60:40 (v/v). The flow rate was 1.0 ml/min and the eluent was monitored at 297 nm. The proposed method was validated as per ICH guidelines.

Result:

The obtained results showed that the compounds were sensitive to hydrolytic decomposition in aqueous media, resulting in the splitting of the hydrazone bond. Rapid hydrolysis of substances was observed in the acid medium. The elevated temperature significantly accelerated the hydrolytic reaction. Relatively slow hydrolysis of 3a-c was observed in a neutral solution and aqueous solutions buffered to pH 9. The hydrolysis of 3a-c in neutral, alkaline and strong alkaline medium followed the pseudo- first-order reaction rate and showed a linear dependence of lnC versus time.

Conclusion:

A validated high-performance liquid chromatographic assay for the determination of the hydrolytic stability of a series of aroylhydrazones was developed and optimized for the first time. The methods devised are successfully applicable to the development of pharmaceutical formulations.