Gradient HPLC separation of dehydroepiandrosterone (DHEA) from its metabolites and biological congeners: role of tetrahydrofuran in the chromatographic mechanism.

A three-step gradient reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the separation of dehydroepiandrosterone (DHEA), its sulfate ester (DHEA-S), its three C7-oxidized metabolites (7alphaOH-DHEA, 7betaOH-DHEA, 7-keto-DHEA), and its biosynthetic congeners (androstenedione, testosterone, estradiol, pregnenolone). This new method allows the quantitative characterization of DHEA metabolism and biosynthetic transformation under given physiological, pathological, or therapeutically influenced circumstances. Tetrahydrofuran probably acts as a proton acceptor coadsorbent, while isopropanol behaves as a proton donor during the separation of testosterone, estradiol, and the stereoisomers of 7-OH-DHEA.

[Pharmaceutical chemistry of minor analgesics and non-steroidal antiinflammatory agents].

The paper represents the last (6th) part of a series about agents acting on the central nervous system. This time the minor analgesics and the non-steroidal antiinflammatory agents are surveyed. As previously, the material is divided into chapters of history, preparation; structure-properties-activity; therapeutical use; analysis.

Evaluation of CD detection in an HPLC system for analysis of DHEA and related steroids.

The biological importance of dehydroepiandrosterone (DHEA) is reflected by the fact that DHEA is a crucial precursor of the biosynthesis of the steroidal sex hormones. Simultaneous separation of DHEA, dehydroepiandrosterone sulfate (DHEA-S), pregnenolone, androstenedione and testosterone has been accomplished by reversed-phase ion-pair high-performance liquid chromatography (RP-IP-HPLC) based on isocratic elution applying circular dichroism (CD) detection at 295 nm. Addition of tetrabutylammonium hydrogensulfate to the mobile phase increases the retention of DHEA-S on the C8-silica column by an apparent ion-pairing mechanism without affecting the retention of the other (non-ionic) steroids.

[Pharmaceutical chemistry of major analgesics].

The paper represents the 5th part of a series about agents acting on the central nervous system. This time the major analgesics are surveyed. As previously, the material is divided into chapters of hystory-preparation; structure-properties-activity; therapeutical use; analysis.