History discovery of free radicals

Free radicals are chemical species which have unpaired electrons on the boundary (atomic or molecular) orbitals.

The term “radical” was first introduced by Guyton de Morveau in 1786 and later used by Gay-Lussac, Liebig, and Berzelius to indicate groups of atoms which were found unchanged in many substances.

For the first time in 1900, Moses Gomberg, Professor of Chemistry at the University of Michigan, speculated the existence of an organic free radical, triphenyl methyl radical (Ph3C•) in the living system.

He published a sensational article entitled ‘Triphenylmethyl, a case of trivalent carbon’, having initiated a new field in organic chemistry, namely, the chemistry of free radicals in solutions.

The scientific community began recognizing the importance of free radicals in 1929, when Friedrich Paneth and Wilhelm Hofeditz produced the methyl free radical, CH3. They prepared the free radical methyl (⋅CH3), by pyrolysis of tetramethyl lead using an adaptation of the system used by Bonhoeffer to study atomic hydrogen.

Later in 1954, Gershman proposed “free radical theory of oxygen toxicity”, according to which, the toxicity of oxygen is due to its ability to form free radicals.

In the same year, the electron paramagnetic resonance (EPR) studies by Commoner in 1954 confirmed the presence of free radicals in biological materials.

In medicine, understanding free radicals, particularly those formed by oxygen, has illuminated the nature of oxidative stress — damage that results when free radicals form faster than the body removes them. This, in turn, has revealed ways human health can be improved — for example, by using antioxidants.
History discovery of free radicals

History of lipoic acid

Lipoic acid is widely distributed in the tissues of animals and plants and in microorganisms.

R-Lipoic acid was first discovered in 1937 by Snell and coworkers, who found that certain bacteria needed a compound from potato extract for growth.

Lipoic acid gained attention in the late 1940s as a growth factor and essential cofactor for pyruvate oxidation in certain microorganisms.

Based on these properties, trivial names including acetate-replacing factor, pyruvate oxidation factor, and protogen A were used to indicate the biologically active substance.

The combined efforts of Lester Reed and the Eli Lilly industrial group led to the first isolation of crystalline acetate-replacing factor in the early 1950s.  They purified 30 mg of a yellow crystalline substance from 100 kg of liver residue. In the following years the molecular structure was elucidated.

An antioxidant action of lipoic acid was proposed for the first time by Rosenberg and Culik in 1959. In Arch Biochem Biophysics (1959;80:86-93), they observed that lipoic acid reduced scurvy in vitamin C –depleted guinea pigs and prevented vitamin E deficiency in rats.
History of lipoic acid