Analyses of compound libraries obtained by high-throughput parallel synthesis: strategy of quality control by high-performance liquid chromatography, mass spectrometry and nuclear magnetic resonance techniques.

The growing interest in combinatorial chemistry has led to a new source of compounds from which a large number of leads has emerged over recent years. Parallel synthesis, in particular, allows a quick production of a wide number of individual compounds. A rapid analytical control is needed to determine their quality. A strategy using automated, fast reversed-phase C18 high-performance liquid chromatography with diode-array detection (LC-DAD-MS) followed by atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) and NMR has been developed for their characterisation and purity control. Complementary NMR analyses are done on selected compounds to provide a better structural characterisation of the expected compounds and their potential side-products. Validated libraries are then registered in ISIS databases using automated procedures.

Amphiphilic alpha-tocopherol analogues as inhibitors of brain lipid peroxidation.

Neurological disorders, such as stroke, trauma, tardive dyskinesia, Alzheimer's and Parkinson's diseases, may be partially attributed to excessive exposition of the nervous tissue to oxygen-derived radicals. A novel water-soluble alpha-tocopherol analogue, 2,3-dihydro-2,2,4,6,7-pentamethyl-3-(4-methylpiperazino) methyl-1-benzofuran-5-ol dihydrochloride (MDL), is a potent radical scavenger. Following subcutaneous administration to mice, MDL inhibited the lipid peroxidation induced in the 100-fold diluted brain homogenates, with an ID50 of 8 mg/kg. Rapid brain penetration, within 30-60 min postadministration, and even distribution into different brain areas were observed. MDL was also detected after oral administration. In brain homogenate undergoing lipid peroxidation, MDL prevented the consumption of an equal amount of alpha-tocopherol, while inhibiting the concomitant malondialdehyde formation. The radical scavenging capacity of MDL was superior to that of alpha-tocopherol, although the peak and half-peak potentials were not significantly different. However, MDL was much less lipophilic, the partition coefficient (log P) at the octanol/water interface being 1.91. Although it is yet unknown, whether the applied criteria sufficiently predict its usefulness, beneficial effects of MDL may be expected in the above mentioned disorders.

Cardioselective ammonium, phosphonium, and sulfonium analogues of alpha-tocopherol and ascorbic acid that inhibit in vitro and ex vivo lipid peroxidation and scavenge superoxide radicals.

Analogues of alpha-tocopherol and ascorbic acid with permanently cationic substituents, i.e., phosphonium (8, 9), sulfonium (11), acylhydrazinium (13, 14), and ammonium (1, 16, 21), were synthesized, and the 2R and 2S enantiomers of the alpha-tocopherol analogues 1, 8, 11, and 13 were separated. The compounds were found to scavenge lipoperoxyl and superoxide radicals in vitro and accumulate in heart tissue (cardioselectivity) as demonstrated by measurement of ex vivo inhibition of lipid peroxidation in mouse heart homogenates and confirmed by HPLC determination of drug concentrations for 1 and 11. The 2R and 2S enantiomers of 1 inhibited ex vivo lipid peroxidation to an equal extent. Thus the in vivo uptake into myocytes (cardioselectivity) is independent of the geometry at the chiral center and common to permanently cationic compounds.