betadex and cyclohexyl-methylphosphonic-acid

Detoxification mechanisms of the chemical warfare agent cyclosarin (GF) in presence of 6-OxP-CD were investigated in detail in in vitro model systems. Most important finding was the preference of 6-Ox-P-CD to eliminate the more toxic (-)-GF. However, elimination of GF enantiomers was dependent on the 6-OxP-CD:GF ratios showing decreasing stereoselectivity and speed of the reaction with increasing GF concentrations. Formation of covalent mono, bis, tris and tetrakis conjugates ((CHMP)n-6-OxP-CD) and appearance of small molecular fragments (SMF) as possible decomposition products after consumption of 6-OxP-CD could be observed.. Interestingly, the non-toxic metabolite O-cyclohexyl methylphosphonic acid (CHMPA) and covalent mono and bis conjugates of 6-OxP-CD and GF were immediately formed, indicating that GF elimination proceeds along different pathways. These important new insights provide information about the mode of action of 6-Ox-P-CD including the role of the pyridinium aldoxime group on the cyclodextrin ring. They are the basis for further investigations in biological media, which could eventually lead to approval of 6-OxP-CD as a new antidote against nerve agent toxicity.

Topics: Antidotes; beta-Cyclodextrins; Organophosphorus Compounds; Oximes; Stereoisomerism

Cyclodextrins (CD) are promising small molecular scavengers showing favourable degradation of extremely toxic organophosphorus compounds (OP) such as tabun (GA), soman (GD) or cyclosarin (GF). For β-CD derivatives as potential OP antidotes with low intrinsic toxicity it is of great interest to completely understand the modes of interaction of both compounds in terms of OP detoxification. The mechanisms of CD action are not completely understood which prompted us to investigate the interactions of GF and β-cyclodextrin (β-CD) as model compounds. Using positive electrospray ionization mass spectrometry (ESI/MS), the formation of covalent conjugates of β-CD with O-cyclohexylmethylphosphonate (CHMP) residue was detected for the first time and was examined in vitro. With a newly developed LC-MS method the formation of O-cyclohexylmethylphosphonic acid (CHMPA) (i.e. GF hydrolysis) and covalent CHMP-β-CD conjugates was analyzed. Compared to water, tris(hydroxymethyl)aminomethane (TRIS) reduced the formation of covalent conjugates but amplified formation of CHMPA. Depending on experimental conditions the degradation of GF by β-CD may be preferably catalytic or stoichiometric. For illustrating different possible reaction pathways a scheme was established that could support the idea of β-CD acting as an artificial enzyme. These results provide an important insight into the β-CD mediated detoxification pathways of GF.

Topics: Antidotes; beta-Cyclodextrins; Buffers; Catalysis; Chemical Warfare Agents; Cholinesterase Inhibitors; Chromatography, High Pressure Liquid; Hydrolysis; Insecticides; Kinetics; Models, Molecular; Molecular Structure; Organophosphorus Compounds; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry; Tromethamine