Physicochemical Profiling of α-Lipoic Acid and Related Compounds.
Lipoic acid, the biomolecule of vital importance following glycolysis, shows diversity in its thiol/disulfide equilibria and also in its eight different protonation forms of the reduced molecule. In this paper, lipoic acid, lipoamide, and their dihydro derivatives were studied to quantify their solubility, acid-base, and lipophilicity properties at a submolecular level. The acid-base properties are characterized in terms of six macroscopic, 12 microscopic protonation constants, and three interactivity parameters. The species-specific basicities, the pH-dependent distribution of the microspecies, and lipophilicity parameters are interpreted by various intramolecular effects, and contribute to understanding the antioxidant, chelate-forming, and enzyme cofactor behavior of the molecules observed.
Department of Pharmaceutical Chemistry, Semmelweis University, Hőgyes Endre utca 9, H-1092, Budapest.|Research Group of Drugs of Abuse and Doping Agents, Hungarian Academy of Sciences, Széchenyi István tér 9, H-1051, Budapest.
Arash
A
Mirzahosseini
Department of Pharmaceutical Chemistry, Semmelweis University, Hőgyes Endre utca 9, H-1092, Budapest.|Research Group of Drugs of Abuse and Doping Agents, Hungarian Academy of Sciences, Széchenyi István tér 9, H-1051, Budapest.
András
A
Szilvay
Department of Pharmaceutical Chemistry, Semmelweis University, Hőgyes Endre utca 9, H-1092, Budapest. noszal.bela@pharma.semmelweis-univ.hu.|Research Group of Drugs of Abuse and Doping Agents, Hungarian Academy of Sciences, Széchenyi István tér 9, H-1051, Budapest. noszal.bela@pharma.semmelweis-univ.hu.
Béla
B
Noszál
D000975:Antioxidants / Q000737:chemistry*; D002627:Chemistry, Physical; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D012995:Solubility; D013816:Thermodynamics; D008063:Thioctic Acid / Q000737:chemistry*
D000975:Antioxidants; D008063:Thioctic Acid
Acid-base; Lipoic acid; Lipophilicity; Microspeciation; NMR-pH titration; Solubility