Electrochemical simulation of cocaine metabolism-a step toward predictive toxicology for drugs of abuse

Fmoc solid-phase synthesis of RF9 optimization with mass spectrometry verification

The RF9 compound, which is an antagonist of the FF neuropeptide receptors is used as a therapeutic substance to improve the effectiveness of opioids in the chronic treatment of pain. The purpose of this study was to find the most efficient method of RF9 synthesis. The optimization experiment involved solid-phase peptide synthesis. The Fmoc strategy is based on the usage of the 9-fluorenylmethoxycarbonyl group to block reactive amino groups. Commonly applied RF9 synthesis is based on DIC/HOBt activation of 1-adamantanecarboxylic acid prior to its substitution. The experiments carried out in this research were based on the routinely applied DIC/HOBt carboxylic group activation and this scheme was compared with the COMU/DIPEA and DIC approach. The obtained results showed that COMU/DIPEA was the most efficient and effective method of RF9 synthesis. Using this strategy, pure compound was obtained, without any by-products, and at a highest yield. The use of COMU/DIPEA can be an excellent alternative to the routinely used RF9 synthesis.

Electrochemistry Investigation of Drugs Encapsulated in Cyclodextrins

The biological electron transfer reactions play an important role in the bioactivity of drugs; thus, the knowledge of their electrochemical behavior is crucial. The formation of radicals during oxidation or reduction, the presence of short-living intermediates, the determination of reaction mechanisms involving electron and proton transfers, all contribute to the comprehension of drug activities and the determination of their mode of action and their metabolites. In addition, if a drug is encapsulated in the cyclodextrin cavity, its electrochemical properties can change compared to a free drug molecule. Here we describe the combination of cyclic voltammetry, UV-Vis spectroelectrochemistry, GC-MS, HPLC-DAD, and HPLC-MS/MS as techniques for evaluating the oxidation mechanism of a drug encapsulated in the cavity of a cyclodextrin. The cavity of cyclodextrin plays a significant role in increasing the stability of the encapsulated products; therefore the identification of oxidation intermediates as semiquinone and benzofuranone derivatives of quercetin is possible in these conditions. The differences in oxidation potentials of the bioactive flavonol quercetin and its cyclodextrin complex relating to its antioxidant activity and the oxidation mechanism are herein discussed.

Synthesis of the Novel Covalent Cysteine Proteases Inhibitor with Iodoacetic Functional Group

This work presents the synthesis of the novel covalent inhibitor of cysteine proteases where epoxide has been replaced by the iodoacetyl functional group. The molecule, similar in action to E-64 and DCG-04, the commonly applied inhibitors, is additionally biotinylated and contains tyrosyl iodination sites. The Fmoc solid phase synthesis has been applied. Conjugation of iodoacetic acid with the peptide was optimized by testing different conjugation agents. The purity of the final product was verified by mass spectrometry and its bioactivity was tested by incubation with a model cysteine protease—staphopain C. Finally, it was shown that the synthesized inhibitor binds to the protein at the ratio of 1:1. More detailed analysis by means of tandem mass spectrometry proved that the inhibitor binds to the cysteine present in the active site of the enzyme.