Substituent effect of ring-substituted 3-hydroxynaphthalene-2-carboxanilides and 2-hydroxynaphthalene-1-carboxanilides in relation to their electrochemical and biological activity

Abstract

• Voltammetric behaviour of novel anti-infective agents was investigated. • Correlation of their electrochemical and biological properties was investigated. • Good relationships were observed between the oxidation potential and antitrypanosomal activities. Two groups of novel anti-infective agents, 3-hydroxynaphthalene-2-carboxanilides and 2-hydroxynaphthalene-1-carboxanilides, were studied by voltammetric techniques at the glassy carbon electrode in aqueous media. Oxidation of hydroxyl group was observed for all forty-four studied compounds, all of them differentiated by a position and a substituent on the benzene moiety. A shift of the oxidation potential was observed for all cases based on electron-donating or electron-withdrawing properties of substituents. These shifts were successfully correlated with Hammett σ substituent constants for meta- and para- substituted compounds. The observed differences in electrochemical behaviour (a shift of the oxidation potential of the unsubstituted compound, and the changes in the value of the reaction constant ρ) between the two studied groups were highlighted and discussed. In addition, an attempt was made to correlate the electrochemical behaviour with the previously obtained in vitro anti-infective (antibacterial, antimycobacterial, antiprotozoal) activities and herbicidal activity. Due to the moderate activity only limited conclusions could be made. However, good relationships were observed between the oxidation potential and antitrypanosomal activities.