Lathosterol side chain amides: a new class of human lathosterol oxidase inhibitors.

Inhibition of cholesterol biosynthesis offers the opportunity for treatment of cardiovascular diseases. Numerous enzymes are involved in the post-squalene part of this biosynthesis, and selective inhibitors for almost all of the enzymes involved there have been described in literature. The only exception is the enzyme lathosterol oxidase (EC 1.14.21.6), for which up to now no selective inhibitor has been found. Up to date only triarimol has been reported as a weak inhibitor. In this paper we report on lathosterol side chain amides as a new class of selective lathosterol oxidase inhibitors. To study the influence of different sterol amides on inhibition of this enzyme, numerous compounds were prepared and the sterol patterns resulting from incubation of HL 60 cells with these enzyme inhibitors were monitored in a whole cell screening assay by means of GC/MS analysis. Small alkyl residues at the amide nitrogen (hydrogen and methyl) lead to an inhibition of the enzyme Delta24-reductase, the N-ethyl and N-propyl derivatives show a dual action, inhibiting both Delta24-reductase and lathosterol oxidase. Lathosterol-derived amides with larger substituents (butyl, isobutyl, tert-butyl, pentyl) at the amide nitrogen were found to be selective inhibitors of lathosterol oxidase. The corresponding 3beta-acetoxy derivatives showed comparable activities and can be considered as prodrugs, since they are transformed into the 3beta-hydroxy derivatives under the test conditions, as proven by HPLC analysis.

Fast and easy in vitro screening assay for cholesterol biosynthesis inhibitors in the post-squalene pathway.

A whole-cell assay for screening cholesterol biosynthesis inhibitors in the post-squalene pathway has been developed. HL 60 cells were incubated for 24h with test substances. The nonsaponifiable lipids were extracted by means of liquid-liquid extraction using tert-butylmethylether. The raw extracts were purified by dispersive solid phase extraction using a primary-secondary amine material (PSA) and dried using sodium sulphate. The sterols were derivatized using N-trimethylsilylimidazole. GLC/MS analysis was carried out in less than 12.5 min using fast GLC mode. The obtained sterol patterns indicated which enzyme had been inhibited. Specific sterol patterns which reflect the different enzyme inhibitions were obtained using established inhibitors of cholesterol biosynthesis like AY 9944, NB 598, clotrimazole, aminotriazole and DR 258, a Delta24-reductase inhibitor prepared in our working group. For characterizing IC(50) values we used sodium 2-(13)C-acetate and quantified the incorporation of it into cholesterol relative to control levels after the samples had been normalized to their protein content.

Multiresidue analytical method using dispersive solid-phase extraction and gas chromatography/ion trap mass spectrometry to determine pharmaceuticals in whole blood.

A convenient analytical method for the simultaneous determination of more than 40 pharmaceuticals belonging to various therapeutic categories in whole blood has been developed. Exemplarily, the method was fully validated for eight different pharmaceuticals. The procedure entails addition of acetonitrile, magnesium sulfate and sodium chloride to a small amount of blood, then the mixture is shaken intensively and centrifuged for phase separation. An aliquot of the organic layer is cleaned up by dispersive solid-phase extraction employing bulk sorbents as well as magnesium sulfate for the removal of residual water. This method was based on the QuEChERS approach developed for pesticide residue analysis in food. Gas chromatography/ion trap mass spectrometry (GC/MS) with electron (EI) and chemical (CI) ionisation was then used for qualitative and quantitative determination of the pharmaceuticals. The dispersive SPE with PSA (sorbent functionalized with primary and secondary amines) was found more suitable than aminopropyl and a styrene-divinylbenzene sorbent for sample clean-up before drug level determination in whole blood and plasma, as it was found that most of endogenous matrix components were removed and the analytes were isolated from spiked samples with recoveries above 80%. Variation coefficients of the repeatability typically smaller than 10% have been achieved for a wide range of the investigated substances. The used analytical conditions allowed to separate successively a variety of drugs and poisons with the typical limit of detection at <20 ng mL(-1) levels using 1 microL injection of equivalent blood sample in whole blood. The method is simple, rapid, cheap and very effective for therapeutic drug monitoring and forensic chemistry.