A NIR, 1H-NMR, LC-MS and chemometrics pilot study on the origin of carvedilol drug substances: a tool for discovering falsified active pharmaceutical ingredients.

Falsification of drugs, entailing the use of drug substances from unknown unapproved suppliers, is one of the main concerns for the quality of medicines. Therefore, traceability of active ingredients represents an effective tool to fight the illegal trade of medicinal products. In this view, the present pilot study explores the profile of carvedilol active ingredients and possible differences related to the origin. Sixteen samples were examined by near-infrared spectroscopy (NIR), proton nuclear magnetic resonance (1H-NMR spectrometry) and liquid chromatography mass spectrometry (LC-MS) Q-TOF and the data were analysed by principal component analysis (PCA), cluster analysis and PLSDA discriminant analysis. The results evidenced that the combined information from the three techniques gave good classification of the samples neatly distinguishing the APIs from European countries from the APIs manufactured out of Europe. In particular, NIR spectroscopy provided effective separation between European and non-European manufacturers and 1H-NMR or LC-MS added specific information related to the separation. Concerning LC-MS Q-TOF, the analysis of multiple isobaric peaks proved to be highly predictive of the drug substance origin and emerged as a promising tool in the field of medicine traceability.

Comparison of reversed-phase enantioselective HPLC methods for determining the enantiomeric purity of (S)-omeprazole in the presence of its related substances.

A simple analytical high-performance liquid chromatography (HPLC) method was applied for the enantiomeric excess determination of esomeprazole ((S)-OME), the enantiopure active ingredient contained in drug products, in the presence of its potential organic impurities A-E. The enantioselective separation was accomplished on the immobilized-type Chiralpak ID-3 chiral stationary phase (CSP) under reversed-phase conditions. The results were evaluated and compared with those obtained by the official enantioselective method of European Pharmacopoeia used as the reference for checking the enantiomeric excess of (S)-OME. It has been established that the use of the Chiralpak ID-3 CSP allows the determination of the enantiomeric purity of (S)-OME without any interference coming from its chiral and achiral related substances. The analytical procedure of the drug regulatory agencies based on the AGP CSP suffered instead from poor specificity due to overlap of the peaks pertinent to the achiral impurity A and the chiral impurity (R)-OME (impurity F).

Characterization of Sildenafil analogs by MS/MS and NMR: a guidance for detection and structure elucidation of phosphodiesterase-5 inhibitors.

Novel synthetic analogs of Sildenafil are constantly detected as adulterants in counterfeit drugs and dietary supplements. Their intake constitutes a serious health hazard as side effects are unknown. In this paper an investigation is carried out on NMR and MS/MS spectra of Sildenafil, Thiosildenafil, Acetildenafil and thirteen of their analogs: a list of key signals is reported and discussed with the intent to provide a tool that can help in detecting adulteration and in elucidating the structure of novel analogs. In this view extensive spectral data were reported, discussed and summarized in tables. A discussion on mass fragmentation and NMR chemical shifts is also provided to rationalize assignation. Moreover, a comprehensive information on the route of synthesis is provided for the benefit of those medicines control laboratories that need to synthesize analogs reference standards in-house.

Quantitative analysis of iobitridol in an injectable preparation by 1H NMR spectroscopy.

Nuclear magnetic resonance spectroscopy was used for direct quantitative determination of iobitridol in an injectable formulation. The method was developed on a medium field strength magnet (400MHz) and validation was performed by assessing specificity, accuracy, precision, linearity, stability of samples and robustness. Validation data confirm that the method is highly appropriate for direct quantification of iobitridol in the final formulation. Moreover the method has a good potential for rapid screening analyses due to straightforward experimental setup and lack of any sample pretreatment.

Synthesis and pharmacological evaluation of bivalent antagonists of the nociceptin opioid receptor.

Bivalent ligands constituted by two identical pharmacophores structurally related to the Nociceptin Opioid Receptor (NOPr) antagonist JTC-801 were synthesized and their binding affinities for NOPr were evaluated. The novel ligands are formed by two modified JTC-801 units linked by di-iminic and di-aminic spacers with length ranging from three to ten methylene units. Moreover, the synthesis and the pharmacological characterization were extended to the corresponding univalent ligands. The latter compounds consisted in a single modified JTC-801 unit and an alkyl or alkylamino or alkylimino tail. The purpose of this study is to feature the location and surroundings of the allosteric binding site(s) of pharmacophores containing the 4-aminoquinoline structure. Most important, the bivalent ligands were exploited to reveal the eventual occurrence of a supramolecular receptorial architecture of the NOPr. All the bivalent derivatives 4 and 5 proved to be active in the nanomolar range with no outstanding dependence on the chain length. They showed potencies from three to ten times higher than the corresponding monomers. Consequently, results clearly indicated a positive role of the second pharmacophore in the ligand-protein interaction. The pharmacological profile of the monomers 7 and 8 clarified the contribution of the linker chain to NOP receptor affinity and suggested the presence of a lipophilic acidic site neighbouring the binding site of the JTC-like ligands. Selectivity of saturated compounds 5, 7, and 8 was tested by binding experiments on δ, κ and µ opioid receptors. Results indicated a general loss of selectivity as compared to JTC-801. In the [(35)S]GTPγS binding assay, all the compounds revealed antagonistic properties at the NOP Receptor. In conclusion the present study set the basis for a systematic investigation on the structural modifications that can be introduced into novel ligands for NOPr and helped to feature the surrounds of the allosteric site of NOPr.

Synthesis and pharmacological evaluation of 1,2-dihydrospiro[isoquinoline-4(3H),4'-piperidin]-3-ones as nociceptin receptor agonists.

Some synthesized 1,2-dihydrospiro[isoquinoline-4(3 H),4'-piperidin]-3-ones were evaluated as ligands for nociceptin receptor (NOP receptor). Their affinity was established by binding studies, and efficacy was investigated by GTP binding experiments. Selectivity toward DOP, KOP, and MOP receptors was assessed, and structural requirements affecting affinity and selectivity were remarked. Most notably, compound 6d displayed nanomolar NOP receptor affinity and showed more than 800-fold selectivity. The new structures exerted full or partial agonistic activity.

Synthesis of new 4-heteroaryl-2-phenylquinolines and their pharmacological activity as NK-2/NK-3 receptor ligands.

Substituted 4-heteroaryl-2-phenylquinolines were synthesized and tested on NK-2 and NK-3 receptors in order to get a better insight in the structure-activity relationship. On the whole, these molecules, which can be regarded as bioisosters of the NK-3 antagonist SB 218795, displayed a lower activity than the template. Ring electronic distribution and H-bond donor and acceptor positions played some role in selectivity, 2-imidazolyl substituted 2a showing affinity mainly towards NK-3 while 3-pyrazolyl substituted 4 displayed a preferential interaction with NK-2 receptor. Structural characterization of the synthesized compounds was achieved by NMR and mass techniques. Bidimensional 1H-NOESY experiments were a helpful tool for the assignment of the isomeric structures of compounds 9 and llb-c.

Synthesis and evaluation as NOP ligands of some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines].

Some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones 3 and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines] 4 were synthesized and evaluated as ligands of the nociceptin receptor. The examined compounds showed partial agonistic activity, except compounds 3, 4n that proved to be pure antagonists.

A new synthetic approach of N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl)benzamide (JTC-801) and its analogues and their pharmacological evaluation as nociceptin receptor (NOP) antagonists.

A series of 4-amino-2-methylquinoline and 4-aminoquinazoline derivatives, including the reference NOP antagonist JTC-801, were synthesized by an alternative pathway and their in vitro pharmacological properties were investigated. 3-Substitution of the quinoline ring resulted very critical for affinity. So 3-methyl derivative 4j showed a similar potency compared with the reference 4h while bulky lipophilic or electron withdrawing groups in the same position strongly decreased affinity. Structural and conformational requirements for affinity were outlined by NOE NMR and computational methods and suggestions for a pharmacophore model design were provided.