title: Complexation of lappaconitine with glycyrrhizic acid: stability and reactivity studies.
abstract: NMR and UV-vis spectroscopy have been used to study the complexation of antiarrhythmic alkaloid lappaconitine with an efficient complexing agent from licorice, glycyrrhizic acid, which is known to profoundly influence the therapeutic activity of the alkaloid in the complex. In MeOH, DMSO, or aqueous solutions, lappaconitine has been shown to form a stable complex with glycyrrhizic acid with 1:1 stoichiometry over a broad concentration range from 1 microM to 300 microM. The stability constant K(11) equals 2.0 x 10(5) M(-1) in aqueous solution. A similar complex of lappaconitine hydrobromide--the pharmaceutical formulation used in the treatment of arrhythmia--is 2 orders of magnitude less stable than pure lappaconitine. A notable decrease in the rate of the photoinduced electron-transfer reaction between lappaconitine in a complex with glycyrrhizic acid and tyrosine allows the suggestion of an explicit interrelation between the suppressed chemical reactivity of the bound alkaloid and the changes of its therapeutic efficiency.
authors.affiliation: Institute of Chemical Kinetics & Combustion, Institutskaya Str. 3, 630090, Novosibirsk, Russia. polyakov@ns.kinetics.nsc.ru
authors.forename: Nikolay E
authors.initials: NE
authors.lastname: Polyakov
authors.forename: Vladimir K
authors.initials: VK
authors.lastname: Khan
authors.forename: Marc B
authors.initials: MB
authors.lastname: Taraban
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Leshina
authors.forename: Nariman F
authors.initials: NF
authors.lastname: Salakhutdinov
authors.forename: Genrikh A
authors.initials: GA
authors.lastname: Tolstikov
mesh_terms: D000157:Aconitine / Q000031:analogs & derivatives* / Q000737:chemistry; D000470:Alkaloids / Q000737:chemistry*; D004579:Electron Transport; D019695:Glycyrrhizic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry
chemical_list: D000470:Alkaloids; D014867:Water; D019695:Glycyrrhizic Acid; D000157:Aconitine; C022150:lappaconitine