Nitroxides: 170 Years of History in Biology and Biomedicine

It is known that there are delicate links and fine parallels between an art and science. Both these spheres of human endeavor involve a unique combination of professional skill and creative search. Sometimes an intuitive line of a great poet or philosopher may be likened to the opening of a new horizon in science. Thus, the composer Maurice Ravel in his famous “Bolero” allegorically depicts the process of birth and development of an epochal discovery that gives rise to many advantages. At first, a musical tune arises whose sound is so weak, so feeble, that it can be easily drowned out by the surroundings. In the second movement, the music is repeated with the same melody, but now with an additional hue. The process repeats itself, again and again, until eventually the most powerful strains of bold, majestic music are then performed by the symphonic orchestra. Like that opening musical movement, the initial publications on the chemistry and application of a novel class of stable radicals, nitroxides, were first met with skepticism, and even strong criticism, from qualified and very professional members of the scientific community. But, later, more and more young enthusiasts joined the ranks of scientists applying this new tool in their research, and ever increasing reports of nitroxides were published in the various fields of chemistry, physics, biology, material science, and biomedicine. The theoretical and experimental data presented in this review clearly demonstrate both history and the current progress within the nitroxide “empire.