Development and validation of an analytical method using High Performance Liquid Chromatography (HPLC) to determine ethyl butylacetylaminopropionate in topical repellent formulations

ABSTRACT Diseases caused by insects are frequent in poor countries, leading to epidemic scenarios in urban areas; e.g., Dengue, Zika and Chikungunya. For this reason, the development of a safe and efficient topical formulation is essential. Ethyl butylacetylaminopropionate (EB) is a mosquito repellent developed by Merck, which is used in products for adults, children and especially babies, due to its low allergenic potential. The aim of this work was to validate an analytical methodology to quantify EB in a new poloxamer-based formulation by high-performance liquid chromatography (HPLC). The quantification methodology was performed at 40 ºC using a Kromasil reverse-phase column (C18), with the dimensions of 250 x 4.6 mm. The mobile phase was acetonitrile:water (1:1) at a 1.0 mL/min flow-rate. The detector wavelength was set at 218 nm to detect EB. The methodology was considered validated since the results indicated linearity (R2>0.99), specificity, selectivity, precision and accuracy (active recovery between 98% and 102%). It also presented limits of detection and quantification of 0.255 µg/mL and 0.849 µg/mL, respectively. The present study demonstrated the EB vehiculated in poloxamer gel is promising as a new insect repellent formulation, since it could be quantified and quality control evaluated.

Rational use of antioxidants in solid oral pharmaceutical preparations

Antioxidants are currently used as efficient excipients that delay or inhibit the oxidation process of molecules. Excipients are often associated with adverse reactions. Stability studies can guide the search for solutions that minimize or delay the processes of degradation. The ability to predict oxidation reactions in different drugs is important. Methods: This study was conducted to assess the rational use of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), sodium metabisulfite (SMB), propyl gallate (PG) and cysteine (CYS) in tablet formulations of simvastatin and ketoconazole. These antioxidants were evaluated according to stability parameters and the relationship between efficiency of the antioxidant and chemical structure of the drugs. Results were compared with DPPH tests and computational simulations. BHT was most efficient regarding simvastatin stability, and the most effective BHT concentrations for maintaining stability were 0.5 and 0.1%. In relation to ketoconazole, SMB was most efficient for maintaining content and dissolution profile. The evaluation by DPPH showed that the largest percentage of absorbance reduction was observed for PG, while SMB proved most efficient and had lower consumption of DPPH. The same pattern was observed, albeit with lower efficiency, for the other lipophilic antioxidants such as BHT and BHA. The results of the molecular modeling study demonstrated that electronic properties obtained were correlated with antioxidant activity in solution, being useful for the rational development of liquid pharmaceutical formulations but not for solid oral formulations. This study demonstrated the importance of considering stability parameters and molecular modeling to elucidate the chemical phenomena involved in antioxidant activity, being useful for the rational use of antioxidants in the development of pharmaceutical formulations.

Atualmente, antioxidantes são usados como excipientes eficientes, que retardam ou inibem o processo de oxidação de moléculas. Excipientes são frequentemente associados a efeitos adversos. Estudos de estabilidade podem ajudar na busca por possíveis soluções para minimizar ou retardar os processos de degradação. A habilidade de prever as reações de oxidação em diferentes fármacos é importante. O estudo foi conduzido com o objetivo de avaliar o uso racional de hidroxianisol butilado (BHA), hidroxitolueno butilado (BHT), metabissulfito sódico (SMB), galato de propila (PG) e cisteína (CYS) em formulações de comprimidos de sinvastatina e cetoconazol. Eles foram avaliados por parâmetros de estabilidade e pela relação entre a eficiência dos antioxidantes e a estrutura química do fármaco. Os resultados foram comparados com testes de DPPH e simulações em computador. BHT foi mais eficiente com relação a estabilidade da sinvastatina e às concentrações mais eficientes para manutenção de estabilidade foram 0,5 e 0,1%. Com relação ao cetoconazol, SMB foi mais eficiente em manter o conteúdo e o perfil de dissolução. A avaliação por DPPH mostrou que o maior percentual de redução de absorção foi observado para PG, enquanto que SMB mostrou ser mais eficiente e consumir menos DPPH. A mesma tendência foi observada com menos eficiência em todos os outros antioxidantes lipofílicos como o BHT e BHA. Os resultados do estudo de modelagem molecular demonstraram que as propriedades eletrônicas obtidas podem ser correlacionadas com a atividade antioxidante em solução, sendo útil para o desenvolvimento racional de formulações farmacêuticas líquidas, mas não para formulações sólidas orais. Este estudo demonstrou a importância de considerar parâmetros de estabilidade e modelagem molecular para elucidar os fenômenos químicos envolvidos na atividade antioxidante, sendo úteis para o uso racional de antioxidantes no desenvolvimento de formulações farmacêuticas.