Stereoselective aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid by female Dutch rabbits

Importance of stereospecific bioanalytical monitoring in drug development

The role of the bioanalyst in the support of drug discovery and development is described with particular emphasis upon stereospecific assays for the individual optical isomers of chiral drugs. The significance of the stereochemical aspects of pharmacokinetics and drug metabolism in both preclinical and clinical development is summarized and illustrated with reference to the pharmacogenetic polymorphisms of drug oxidation existing in the human population. The significance of stereochemical considerations in drug metabolism and pharmacokinetics has recently become an issue for both the pharmaceutical industry and the regulatory authorities, driven to a great extent by recent developments in methodology for both the analytical and preparative resolution of racemic drug mixtures. Ths has led to the so-called 'racemate-versus-enantiomer' debate in recent years. The development of regulatory attitudes in the major jurisdictions of the world to the development of new drugs containing one or more chiral centres is outlined.

Stereochemical aspects of the hydration of trans-anethole epoxide in the rat

Racemic trans-anethole epoxide [1-(4'-methoxyphenyl)-propane-1,2-oxide] was incubated with water, buffers, and rat liver microsomes and cytosol and the stereochemistry of the diols produced was determined by HPLC as their dicamphanyl esters. The diol metabolites were isolated by HPLC from the urine of rats administered [1'-14C] trans-anethole and their stereochemistry determined after derivatization to their camphanyl esters. The stereochemical course of the metabolism of trans-anethole by rat liver microsomes and cytosol is discussed.

Stereoselectivity of the aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid in rat and guinea pig

Following administration of 6-n-propylchromone-2-carboxylic acid (6-n-PCCA) (500 mumol/kg) to male rats, three metabolic products were detected and isolated from the 0-24 h urine. All were identified as resulting from oxidation exclusively along the 6-n-propyl moiety. Some 66% of the dose was excreted in the 0-24 h urine, 55% of which was 6-PCCA, with 15% as (6-1'-hydroxypropyl)chromone-2-carboxylic acid (6-1'-HPCCA), 22% as 6-(2'-hydroxypropyl)chromone-2-carboxylic acid (6-2'-HPCCA), and 4% as 6-3'-carboxypropyl)chromone-2-carboxylic acid (6-3'-CPCCA). Derivatization of the methyl esters of the hydroxylated metabolites with S-alpha-methoxy-alpha-(trifuloromethyl)-phenylacetyl chloride (Mosher's reagent) allowed the evaluation of urinary enantiomeric composition by HPLC and assignment of their absolute configurations by NMR. This was found to be 90:10 (R/S) for 6-2'-HPCCA, and 7:93 (R/S) for 6-1'-HPCCA. When rats were dosed with the racemic 1'- and 2-hydroxy metabolites; no stereoselective metabolism or excretion was observed. Administration of 6-n-PCCA to male guinea pigs revealed that this species was unable to metabolise this compound.