Scavenging of hydroxyl radical by catecholamines

Culture medium-dependent isoproterenol stability and its impact on DNA strand breaks formation and repair

In vitro mechanistic research is mostly performed without taking into consideration the potential influence of cell culture media and/or their supplements and therefore, interactions between compounds of interest and medium ingredients may be overlooked. Isoproterenol (isoprenaline) is a synthetic catecholamine used as sympathomimetic drug that stimulates β-adrenergic receptors and is widely used in biomedical research. Clinical studies have shown that isoproterenol is rapidly metabolized in the human body with a plasma half-life of about 2-5 min. However, despite its use in many in vitro and ex vivo studies, the stability of isoproterenol in cell culture media has not been characterized. Our results show a decrease of isoproterenol concentration in RPMI medium but high stability of the compound in TexMACS medium. The isoproterenol oxidation product isoprenochrome forms during treatment in both media. However, isoprenochrome formation is significantly lower in TexMACS medium. The effective level of isoproterenol and the formation of oxidation products might explain the discrepancies observed in isoproterenol-induced genotoxicity and cytotoxicity.

The reactivity of neurotransmitters and their metabolites towards various nitrogen-centered radicals: Experimental, theoretical, and biotoxicity evaluation

In the past few years, there has been a certain interest in nitrogen-centered radicals, biologically important radicals that play a vital role in various processes and constitute many important biological molecules. In this paper, there was an attempt to bridge a gap in the literature that concerns the antiradical potency of monoamine neurotransmitters (dopamine, epinephrine, and norepinephrine) and their metabolites towards these radicals. The most probable radical quenching mechanism was determined for each radical out of three common mechanisms, namely Hydrogen Atom Transfer (HAT), Single Electron Transfer followed by the Proton Transfer (SET-PT), and Sequential Proton Loss Electron Transfer (SPLET). Marcus' theory was then used to determine the reaction rates for the electron transfer process. SPLET was the most probable mechanism for both reactions with the aminyl and hydrazyl radicals, while HAT and SPLET were plausible mechanisms for reactions with the imidazolyl radical. Special emphasis was put on the investigation of the substituent effect on the preferred mechanism. The necessity of both thermodynamic and kinetic parameters for the comparison of the antiradical potency of compounds was discussed. The same methodology was applied for the theoretical investigation of the reactivity towards DPPH^⦁, a member of the hydrazyl radicals. An ecotoxicity analysis was performed to assess the impact the investigated radicals have on the ecosystem. Except for histidine, every other neutral form was either toxic or highly toxic to some of the analyzed marine organisms.

Synthesis and activity of a coumarin-based fluorescent probe for hydroxyl radical detection

As a type of reactive oxygen species (ROS), hydroxyl radical (·OH) is closely associated with many kinds of diseases. The present study aimed to develo p a novel OH fluorescent probe based on coumarin, a new compound that has not been previously reported. This probe exhibited good linear range and selectivity for ·OHl, and is able to avoid interference from some metal ions and other kinds of ROS (H₂ O₂ , O₂ ^.- , ¹ O₂ , and HClO). Meanwhile, this probe has been used to evaluate the ·OH-scavenging efficiency of different compounds, such as isopropyl alcohol, cytosine, uracil, Tempo, Glutathione (GSH), and dimethyl sulfoxide (DMSO). Therefore, the present study shows that this probe not only can effectively measure the level of ·OH, but also can assess the ·OH-scavenging efficiency of different compounds. Furthermore this current study suggested that following further optimization, this probe may be potentially applied in the diagnosis of oxidative stress in human body.

Antiradical activity of catecholamines and metabolites of dopamine: theoretical and experimental study

The importance of molecules with antiradical potency that are produced in the human body has significantly increased. Among others, neurotransmitters and their metabolites act as the first line of defense against oxidative stress in the peripheral endocrine and the central nervous systems. Dopamine (DO), epinephrine (EP), norepinephrine (NE), l-DOPA, catechol, and three metabolites of dopamine (3-methoxytyramine (3-MT), homovanillic acid (HO), and 3,4-dihydrophenylacetic acid (DOPAC)) were investigated for their antiradical potency via computational methods and DPPH assay. Density functional theory calculations were used to determine the most probable reaction mechanism based on the thermodynamic parameters. These results suggested that hydrogen atom transfer (HAT)/proton-coupled electron transfer (PCET) and sequential proton loss electron transfer (SPLET) mechanisms are preferable in polar solvents. Several techniques were employed to differentiate between HAT and PCET mechanisms via examination of the transition state structures. Kinetic studies of HAT/PCET and electron transfer (ET) reactions, the second step of SPLET, have proven that ET is much faster for an order of 10⁵-10⁶. Based on this, it was concluded that SPLET was the dominant mechanism for the antiradical activity towards DPPH radicals in polar solvents. The findings suggest that all the investigated molecules can be classified as excellent antiradical scavengers, except for 3-MT and homovanillic acid.