ABSTRACT
Mitochondria-targeting drugs and diagnostics are used in the monitoring and treatment of mitochondrial pathologies. In this respect, a great number of functional compounds have been made mitotropic by covalently attaching the active moiety onto a triphenylphosphonium (TPP) cation. Among these compounds, a number of molecular detectors for reactive oxygen species (ROS) are based on fluorescent and chemiluminescent probes. In this regard, luminol (probably the most widely known chemiluminescent molecule) has been employed for a number of biological applications, including ROS detection. Its oxidation under specific conditions triggers a cascade of reactions, ultimately leading to the excited 3-aminophthalate (3AP *), which emits light upon deactivation. Hence, the photophysical interaction between the light-emitting species 3AP * and TPP cations needs to be evaluated, as it can add valuable information on the design of novel emission-based mitotropic systems. We herein investigate the quenching effect of ethyltriphenylphosphonium cation onto substituted 3-aminophthalates. These were prepared in situ upon hydrolysis of the corresponding anhydrides, which were synthesized from 3-aminophthalimides. Steady-state fluorescence and time-resolved experiments were employed for the evaluation of a possible electron transfer quenching by phosphonium ions. Our experimental results confirmed such quenching, suggesting it is mainly dynamic in nature. A minor contribution of static quenching that was also detected is attributed to complex formation in the ground state. Accordingly, the chemiluminescence of luminol was indeed strongly reduced in the presence of phosphonium ions. Our results have to be taken into account during the design of new chemiluminescent mitotropic drugs or diagnostic agents of the luminol family.
Subject(s)
Luminescent Measurements , Luminol/chemistry , Organophosphorus Compounds/chemistry , Reactive Oxygen Species/chemistry , Mitochondria/chemistryABSTRACT
The presence of copper(II) in the micromolar range modulates the photodegradation rate of the fluoroquinolone Rufloxacin (RFX), both under air and in nitrogen saturated aqueous solution. The photodegradation rate of RFX under aerobic conditions decreases in the presence of metal ions, and no change in the nature of the photoproducts is observed. In anaerobic media, RFX photodegradation rate increases with increasing copper(II) concentration and the photoproducts distribution changes. Copper(II) inhibits formation of type II products of 2'-deoxyguanosine diagnostic of photosensitization mediated by singlet oxygen. The overall results provide a clear example demonstrating how a bio-compatible trace element influences efficiently not only the bioavailability of a drug but also its molecular mechanism of photodegradation and photosensitization.
