Synthesis of organic salts from 1,10-phenanthroline for biological applications

Abstract

Abstract Molecular 1,10-phenanthroline has superb intercalation ability with DNA base pairs. However, it could not be used for medicinal applications. This is due to its toxicity caused by inhibiting metalloenzymes via its chelating nitrogen atoms. Nonetheless, the toxicity has been avoided for its attractive features coordinating with transition metals. However, this required lengthy synthetic work and rendering the final application is more laborious, expensive and less environmentally friendly. Moreover, this usually results in rigid three-dimensional complexes that prevents the complete intercalation of the coordinated 1,10-phenanthroline with DNA base pairs which diminishes its activity. In this work, an alternative strategy in diminishing the toxicity but retaining the flat geometry of 1,10-phenanthroline following simpler synthetic procedure without the involvement of transition metals is described. This was achieved synthesizing five N-alkyl-1,10-phenanthrolinium bromide salts. The salts were characterized by spectrometry (1H NMR, ESI MS, Uv-vis), CHNBr elemental analysis and conductivity measurements. All demonstrated amphiphilic property, which make their applications convenient. Their in vitro biological activities were tested on two Gram-positive (Staphylococcus aureus (S. aureus) and Streptococcus pyogens (S. pyogenes) and two Gram-negative (Eschercia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) bacteria and compared with 1,10-phenanthroline. They are found active against all the tested bacteria. The minimum inhibitory concentrations of the salts are nearly the same as 1,10-phenanthroline. The increase in the alkyl chain length increased the antibacterial activities of the slats in all the tested bacteria. All the salts demonstrated high molar conductivities.