Identifying impurities in drug substances has become one of the most important issues in pharmaceutical analysis since it can have a significant impact on the efficacy of new pharmaceutical products. Due to the purity requirements, in this paper a new synthetic α2-adrenoceptor agonist, called LPSF-PT-31, was purified and its impurities were characterized by liquid chromatography-multistage mass spectrometry (LC-MSn) and liquid chromatography-solid phase extraction-nuclear magnetic resonance (LC-SPE-NMR). The purification step was conducted using a semi-preparative liquid chromatography and stacked injections as a new approach to drug purification. As a result, a total yield of 75% of the pure LPSF-PT-31 and 2.9 L day-1 in solvent reduction was obtained. The combination of semi-preparative stacking injection, LC-MSn, and LC-SPE-NMR, demonstrated to be efficient to purify active drugs and unambiguously identify its impurities. In addition, isolation and identification of drug impurities in the early stages of development can improve the synthetic pathway, preventing the formation of impurities or minimizing this formation to minimum levels.

We describe herein a straightforward and efficient preparation of 2',3'-dideoxy-2'-(2''- (trimethylsilyl)ethylthio)thymidine, which allows the preparation of diverse potentially antiviral and/or anticancer nucleosides (disulfides, thiols, sulfides, thiocyanates).

Um método rápido e simples de LC-UV (cromatografia líquida com detecção ultravioleta) foi desenvolvido e validado para quantificação do 5-acridina-9-ilmetileno-3-(4-flúor-benzil)-tiazolidina-2,4-diona (LPSF/AC-23) em plasma de ratos utilizando extração por precipitação proteica com acetonitrila, e uma tiazolidinadiona (3-(2-bromo-benzil)-5-(5-bromo-2-metoxi-benzilideno)-tiazolidina-2,4-diona) como padrão interno. A separação e quantificação do LPSF/AC-23 foi realizada utilizando uma fase móvel composta por uma mistura de acetonitrila/metanol/tampão fosfato (55:30:15) elu í da de forma isocrática através de uma coluna analítica C18 seguida de detecção UV a 249 nm. A curva de calibração foi linear na faixa de 100-10.000 ng mL- 1. A precisão intra e interdia apresentou valores de desvio-padrão relativo preconizados pela Agência Nacional de Vigilância Sanitária (Anvisa) e a exatidão, expressa pelo erro relativo, variou de -3,49 a 7,67%. A recuperação foi de 92,25% para o analito e 89,67% para o padrão interno e nenhum interferente endógeno foi observado. Desta forma, o método proposto pode ser aplicado na determinação quantitativa do LPSF/AC-23 em plasma de ratos em estudos farmacocinéticos e de biodisponibilidade.

A quick and simple LC-UV (liquid chromatography with ultraviolet detection) method was developed and validated for quantification of 2,4-thiazolidinedione,5-(9-acridinylmethylene)-3-[(4-fluorophenyl)methyl] (LPSF/AC-23) in rat plasma using protein precipitation extraction with acetonitrile, and a thiazolidinedione 2,4-thiazolidinedione,5-[(5-bromo-2-methoxyphenyl)methylene]-3-[(2-bromophenyl)methyl] as an internal standard. The separation and quantification of LPSF/AC-23 were performed using a mobile phase consisting of a mixture of acetonitrile/methanol/phosphate buffer (55:30:15) eluted in an isocratic manner through a C18 analytical column followed by UV detection at 249 nm. The calibration curve was linear in the range of 100-10,000 ng mL-1. The intra- and inter-day precisions expressed by relative standard deviation values were recommended by the Brazilian Health Surveillance Agency (Anvisa), and accuracy expressed by relative error ranged from -3.49 to 7.67%. The recovery was 92.25% for the analyte and 89.67% for the internal standard and no endogenous interference was observed. Thus, the proposed method can be applied to quantitative determination of LPSF/AC-23 in plasma of rats, in pharmacokinetic and bioavailability studies.

Um método rápido e simples de cromatografia líquida com detecção por ultravioleta foi desenvolvido e validado para quantificação, em plasma de rato, do composto (5Z,E)-3-[2-(4-clorofenil)-2-oxoetil]-5-(1H-indol-3-ilmetileno)-tiazolidina-2,4-diona (PG15). Uma coluna em fase reversa C18 foi utilizada para separação do analito, seguida por detecção em UV a 385 nm. O método utilizou a precipitação do PG15 a partir do plasma e eluição isocrática com metanol:água (90:10, v/v). O tempo total da corrida foi 7,5 min. O método proposto foi validado e mostrou-se linear entre 62,5 e 4000 ng mL-1. A precisão intra- e inter-dia, expressa como desvio padrão relativo, foi menor que 15 e 10%, respectivamente, para todas as concentrações investigadas. A exatidão, medida através dos controles da qualidade, ficou entre 86,1-114,9 %. A aplicabilidade do método validado foi testada no estudo farmacocinético pré-clínico do PG15.

A simple and rapid liquid chromatography-ultraviolet detection (LC-UV) method has been developed and validated for quantifying (5Z,E)-3-[2-(4-chlorophenyl)-2-oxoethyl]-5-(1H-indol-3-ylmethylene)-thiazolidine-2,4-dione (PG15) in rat plasma. A C18 reversed phase column provided chromatographic separation of the analyte which was followed by UV detection at 385 nm. The method involves precipitation of PG15 from plasma and isocratic elution with methanol:water (90:10, v/v). Total elution time was 7.5 min. The proposed method was validated and showed linear correlation in the range of 62.5 to 4000 ng mL-1. The within- and between-day precision, expressed as the relative standard error, were found to be less than 15 and 10 %, respectively, for all the concentrations investigated. The accuracy, measured using the quality control samples, was in the range of 86.1-114.9 %. The applicability of the validated method was tested in a pre-clinical pharmacokinetic study of the thiazolidinone PG15.

The emergence of strains of Schistosoma resistant to praziquantel has drawn attention to the search for new schistosomacide drugs. Imidazolidinic derivatives have performed outstandingly against adult S. mansoni worms when evaluated in vitro. The molecular modification of imidazolidine by way of bioisosteric replacement gives rise to variations in its biological response. This study verifies the potential of substituent groups in the derivatives (Z)3-benzyl-5-(2-fluoro-benzylidene)-imidazolidine-2,4-dione NE4, 3-benzyl-5-(4-chloro-arylazo)-4-thioxo-imidazolidin -2-ona PT5, 3-benzyl-5-(3-fluoro-benzylidene)-1-methyl-2-thioxo-imidazolidin-4-one JT53; 3-benzyl-1-methyl-5-(4-methyl-benzylidene)-2-thioxo-imidazolidin-4-one JT63; 3-benzyl-1-methyl-5-(4-methoxi-benzylidene)-2-thioxo -imidazolidin-4-one JT68; 3-(4-chloro-benzyl)-1-methyl-5-(4-methoxi-benzylidene)-2-thioxo-imidazolidin-4-one JT69; 3-(4-phenyl-benzyl)-1-methyl-5-(4-methoxi-benzylidene)-2-thioxo-imidazolidin-4-one JT72 by determining the viability in vitro of adult S. mansoni worms in the presence of these derivatives. The susceptibility of the worms obtained from mice and kept in culture in the presence of different concentrations was determined by way of schistosomacide kinetic, observed every 24 h over a period of eight days. The results show that the worms were more sensitive to the PT5 derivative at a concentration of 58 µM which killed 100% of the worms after 24 h of contact, also giving rise to alterations in the tegument surface of the worms with the formation of bubbles and peeling. These observations suggest a strong electronic contribution of the arylazo grouping in the biological response.