Reductive activation of benzazolo[3,2-a]-quinolinium chlorides

Area of Science:

• Biochemistry
• Cellular Biology
• Toxicology

Background:

• Ferricytochrome c (Cyt(III)c) reduction is a key step in cellular respiration.
• Understanding the factors influencing Cyt(III)c reduction is crucial for assessing cellular health and potential toxicity.

Purpose of the Study:

• To investigate the initial reduction rates of Cyt(III)c by nitrofurantoin (NFT) and three quinolinium salts (NBQCl, ENBIQCl, EHBIQCL).
• To correlate these reduction rates with the compounds' electrochemical properties (half-wave reduction potentials, E1/2).
• To explore the role of superoxide in Cyt(III)c reduction mediated by these compounds.

Main Methods:

• Measurement of Cyt(III)c reduction rates in aerobic and anaerobic solutions.
• Utilizing xanthine/xanthine oxidase system for generating reactive oxygen species.
• Employing superoxide dismutase (SOD) to assess the contribution of superoxide to the reaction.
• Correlation analysis between reduction rates and E1/2 values.

Main Results:

• Maximum Cyt(III)c reduction rates under anaerobic conditions followed the order: NFT > NBQCL > ENBIQCL > EHBIQCL.
• Reduction rates showed a linear correlation with the E1/2 values of the compounds.
• Cyt(III)c reduction was generally slower in air-saturated solutions compared to nitrogen-saturated solutions.
• Higher SOD concentrations were required for 50% inhibition of Cyt(III)c reduction for compounds with larger E1/2 values.

Conclusions:

• The reduction of Cyt(III)c by NFT and quinolinium salts is influenced by their reduction potentials.
• Superoxide production alone does not fully explain the observed Cyt(III)c reduction rates in air.
• NBQCL, ENBIQCl, and potentially EHBIQCL may disrupt mitochondrial energy metabolism or induce DNA damage via their reduced intermediates.