Study of Nine Aromatic Diamidines Designed to Optimize Their Analysis by HPLC

Abstract

The aromatic diamidines are a series of chemicals with high basicity. Among other properties they have, is that of intervening in the metabolism and transport of polyamines, since they inhibit s‐adenosyl‐L‐methionine decarboxylase (SAMDC) and diamine oxidase (DAO). They are of importance in pharmacology. Examples of this are: that pentamidine is used, for instance, in treating pneumonia in patients affected by the human immunodeficiency virus (HIV), that propamidine is utilized, among other things, to treat cornea infections, and that berenil is employed in veterinary medicine, though not in humans. Owing to their considerable interest, further chemicals belonging to this family are constantly being synthesized, with the aim of ensuring greater pharmacological capacities, better stability, and fewer secondary effects. It is essential to have available analytical methods for detecting these drugs in a range of media. In this study, attention was paid to nine aromatic diamidines that are heads of series: pentamidine, stilbamidine, DAPI, propamidine, hydroxystilbamidine, phenamidine, diampron, berenil, and dibromopropamidine, with the aim of proposing analytical methods employing HPLC. Use was made of ion‐pairing for each of them, and for others of similar structure, in aqueous solutions and in biological media, such as serum and urine. To achieve the purpose of the study, the effects on the capacity factor k′ of varying the chief chromatographic parameters were tracked. These parameters were the influences exercised by: concentration and chain length of the ion‐pair‐forming agent, pH in the mobile phase, methanol percentage, buffer concentration, and temperature. The data obtained from this work suggest general conditions for the analysis of each of these substances in aqueous solution would be a mobile phase consisting of 25.0 mM citrate buffer, with pH = 3.25, methanol 45%, ultrasphere ODS column (5 µm particle size,15 cm × 4.6 mm I.D.), temperature 30°C, flow 1.00 mL/min, and specific conditions for individual chemicals as laid out in Table 1. Under these conditions, detection limits ranging from 45.0 ng/mL for berenil to 5.00 ng/mL for DAPI can be attained.

Keywords:

• Aromatic diamidines
• HPLC

Acknowledgments

We should like to express our gratitude to Rhône Poulenc Rorer Ltd. for their generous donation of all the products studied in this paper. We should like to thank J. Carlos García for his valuable assistance in this work.