Organic Salts of Pharmaceutical Impurity p-Aminophenol
by
U. B. Rao Khandavilli 1,2,*
, Leila Keshavarz 1, Eliška Skořepová 3,4, René R. E. Steendam 1 and Patrick J. Frawley 1
U. B. Rao Khandavilli 1,2,*, Leila Keshavarz 1, Eliška Skořepová 3,4, René R. E. Steendam 1 and Patrick J. Frawley 1
1
Synthesis and Solid State Pharmaceutical Centre (SSPC), Bernal Institute, University of Limerick, Limerick, Ireland
2
PSC Biotech Limited, Blanchardstown, Dublin 15, Ireland
3
Department of Chemical Engineering, University of Chemistry and Technology Prague, Technická 3, 16628 Prague 6, Czech Republic
4
Institute of Physics ASCR, Na Slovance 2, 182 21 Praha 8, Czech Republic
*
Author to whom correspondence should be addressed.
Molecules 2020, 25(8), 1910; https://doi.org/10.3390/molecules25081910
Received: 12 March 2020 / Revised: 11 April 2020 / Accepted: 18 April 2020 / Published: 21 April 2020
(This article belongs to the Section Medicinal Chemistry)
The presence of impurities can drastically affect the efficacy and safety of pharmaceutical entities. p-Aminophenol (PAP) is one of the main impurities of paracetamol (PA) that can potentially show toxic effects such as maternal toxicity and nephrotoxicity. The removal of PAP from PA is challenging and difficult to achieve through regular crystallization approaches. In this regard, we report four new salts of PAP with salicylic acid (SA), oxalic acid (OX), l-tartaric acid (TA), and (1S)-(+)-10-camphorsulfonic acid (CSA). All the PAP salts were analyzed using single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The presence of minute amounts of PAP in paracetamol solids gives a dark color to the product that was difficult to remove through crystallization. In our study, we found that the addition of small quantities of the aforementioned acids helps to remove PAP from PA during the filtration and washings. This shows that salt formation could be used to efficiently remove challenging impurities.
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MDPI and ACS Style
Khandavilli, U.B.R.; Keshavarz, L.; Skořepová, E.; Steendam, R.R.E.; Frawley, P.J. Organic Salts of Pharmaceutical Impurity p-Aminophenol. Molecules 2020, 25, 1910.
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