PEG2-bis(phosphonic acid diethyl ester)

The solvation dynamics after optical excitation of two phosphono-substituted coumarin derivatives dissolved in various solutions are studied by fluorescence up-conversion spectroscopy and quantum chemical simulations. The Kamlet-Taft analysis of the conventional absorption and emission spectra suggests weakening of the solvent-solute H-bonds upon optical excitation, which is in contrast to the results gained by the quantum simulations and earlier studies reported for coumarin derivatives without phosphono groups. The simulations give evidence that the solvent reorganisation around the excited fluorophore leads to partial electron transfer to the first solvation shell. The process occurs on a timescale between 1 and 10 ps depending on the solvent polarity and leads to a fast decay of the time-resolved emission signal. Using the ultrafast spectral shift of the time-dependent fluorescence we estimated the relaxation time of the H-bonds in the electronically excited state to be about 0.6 ps in water, 1.5 ps in ethanol and 2.8 ps in formamide.

NO-1886 ([4-(4-bromo-2-cyano-phenylcarbamoyl) benzyl]-phosphonic acid diethyl ester) increases lipoprotein lipase activity, resulting in a reduction in plasma triglycerides and an increase in high-density lipoprotein cholesterol. The metabolism of NO-1886 in human liver was investigated in the present study. Ester cleavage of NO-1886 from diethyl phosphonate to monoethyl phosphonate was the major metabolic pathway catalyzed by cytochrome P450. In addition, the minor metabolic pathway in human liver was the hydrolysis of the amide bond of NO-1886 by a specific cytosolic esterase. Eadie-Hofstee plots of phosphonate O-deethylation of NO-1886 in human liver microsomes showed a biphasic curve, indicating low- and high-K(m) components. Inhibition experiments with chemical inhibitors and antibodies against various cytochrome P450 isoforms suggested the involvement of CYP2C8 and CYP3A in the phosphonate O-deethylation. Recombinant CYP3A4 and CYP2C8 expressed in baculovirus-infected insect cells and human lymphoblastoid cells exhibited a high activity for phosphonate O-deethylation of NO-1886. The recombinant cytochrome P450 enzymes indicated that CYP2C8 and CYP3A4 were responsible for the low- and high-K(m) components in human liver microsomes, respectively. The selectivity of CYP2C8 in catalyzing phosphonate O-deethylation indicates that coadministration of drugs that are metabolized by the same enzyme requires careful consideration.

By use of 31P-NMR, quasi-elastic light scattering and freeze-fracture electron microscopy it is shown that hexane phosphonic acid diethyl ester (PAE) is incorporated in hepatic microsomes without any alteration of the bilayer structure at two different sites. These findings proved that PAE can be used as molecular 31P-NMR probe in microsomes to get information about lipid-protein interactions. Extensive studies on reconstituted liposomal systems which contained cytochrome P-450 and cytochrome P-450 reductase showed that both proteins influence the localization of incorporated PAE. The results indicate a specific interaction of phosphatidylethanolamine (PE) with cytochrome P-450 in microsomes.