Stereospecific determination of an HIV aspartyl protease inhibitor, PNU-103017, in rat, dog and human plasma using a Pirkle-concept high-performance liquid chromatographic column

Separation, bioactivity, and dissipation of enantiomers of the organophosphorus insecticide fenamiphos

Most chiral pesticides are used as racemates despite the fact that the pesticidal activity of the given pesticide is usually the result of the preferential reactivity of only one enantiomer while the other enantiomers may have toxic effects against other nontarget organisms. Accordingly, the enantiomer of fenamiphos, an organophosphorus pesticide, was separated by high-performance liquid chromatography with reverse phase and normal phase on a Pirkle model chiral stationary phase column. It was found that n-hexane/isopropanol (95/5) was the best solvent system for enantiomer resolution of fenamiphos. Chromatographic data including capacity factor (k'), separation factor (alpha), and resolution (Rs) are presented. Inhibitory activity to enzyme butyrylcholinesterase and toxicity to Daphnia of enantiomers and racemic insecticide fenamiphos were also studied. In the toxicity tests of Daphnia, the lethal concentration (LC50) of (+)-fenamiphos, (-)-fenamiphos, and racemate were 0.0016, 0.0061, and 0.0019 microg/mL, respectively. No significant difference of LC50 values between (+)-fenamiphos and racemate were found, but (-)-fenamiphos showed significantly lower toxicity to Daphnia. The inhibitory concentration (IC50) to the cholinesterase were 0.008, 0.15, and 0.46 microg/mL for (+)-fenamiphos, (-)-fenamiphos, and racemate, respectively. Both enantiomers and the racemate showed significant difference in inhibiting the cholinesterase. However, (+)-fenamiphos proved to be about 20 times more toxic to Daphnia and only about four times more inhibitory activity to butyrylcholinesterase than (-)-fenamiphos. The dissipation of (+)-fenamiphos, (-)-fenamiphos, and racemate in selected soils and natural water samples were also studied. The half-life (t(1/2)) of (+)-, (-)-, and racemate in soils showed no related to the soil texture, pH, or organic carbon content. By comparing the residues of (+)-, (-)-, and racemate in the water, it was found that (+)-fenamiphos was degraded faster than the others after 21 days. Briefly, (+)-fenamiphos is more toxic than (-)-fenamiphos to a nontarget organism (Daphnia), but the environmental persistence of the two compounds showed no significant difference.

Separation and toxicity of enantiomers of organophosphorus insecticide leptophos

Enantiomers of leptophos were separated by high-performance liquid chromatography with a Whelk-O1 column using 3% dichloromethane in n-hexane as mobile phase. Toxicity tests of leptophos enantiomers and racemate were performed with daphnia. Enzyme inhibition of leptohpos was carried out by using butyryl cholinesterase from horse serum and acetylcholinesterase from housefly heads. From the inhibition test of butyrylcholinesterase, the half-inhibitory concentrations, IC(50), of (+)-leptophos, (-)-leptophos, and (+/-)-leptophos were 0.241, 1.17, and 1.05 gmL(-1), respectively. No significant difference in IC(50) in (-)-leptophos and (+/-)- leptophos was found. However, the IC(50) of (+)-leptophos was significantly different from those of the others. In the inhibition test of acetylcholinesterase, the IC(50) values of (+)-leptophos, (-)-leptophos, and (+/-)-leptophos were 14.01, 24.32, and 13.22 gmL(-1), respectively. There was no significant difference in IC(50) in (+)-leptophos and (+/-)-leptophos, although the IC(50) of (-)-leptophos was significantly different from those of the others. From these results, leptophos-both enantiomers and racemate-seems to have higher neurotoxicity for mammals than for the target insects. In the toxicity test of daphnia, the half-lethal concentrations, LC(50), of (+)-leptophos, (-)-leptophos, and (+/-)-leptophos were 0.0387, 0.802, and 0.0409 gL(-1), respectively. There is no significant difference in LC(50) in (+)-leptophos and (+/-)-leptophos. The LC(50) of (-)-leptophos is significantly higher than those of the others. From these results, (-)-leptophos has lower toxicity to daphnia.

Species-dependent enantioselective pharmacokinetics of PNU-103017, a pyrone HIV protease inhibitor

PNU-103017, 4-Cyano-N-(3-(cyclopropyl(5,6,7,8,9,10-hexahydro-4-hydroxy- 2-oxo-2H-cycloocta(b) pyran-3-yl)methyl)phenyl)-benzenesulfonamide, is a selective HIV aspartyl protease inhibitor under evaluation as a potential oral treatment of Acquired Immunodeficiency Diseases. PNU-103017 is a racemic mixture of two enantiomers, designated PNU-103264 (R-) and PNU-103265 (S-). Stereoselective pharmacokinetics of the two enantiomers of PNU-103017 were observed in the dog, rat, and human after single and multiple dose administration of the racemate and were apparently species-dependent. Mean enantiomeric ratios of plasma concentrations (R-/S-) at each time point were greater than 1 in the dog, ranging from 1.22 to 3.06, but less than 1 in the rat and in the human, ranging from 0.44 to 0.80 and 0.23 to 0.73, respectively. A trend towards increased or decreased (farther from 1:1, R-/S-) enantiomeric ratio of plasma concentrations with time after each administration was also observed. The enantiomeric ratio remained unchanged after multiple dose administration in the rat, dog, and human although enzyme induction and increased plasma clearance were observed for both enantiomers.