Influence of positively-charged guests on the superoxide dismutase mimetic activity of copper(II) beta-cyclodextrin dithiocarbamates

The superoxide dismutase (SOD) activity of the Cu(II) complexes of two dithiocarbamate derivatives of cyclodextrin (Cu-C6DTC, Cu-C2DTC), one on the primary (C6DTC) and the other on the secondary (C2DTC) side, was determined in the presence of positively-charged guests which have the general formula RNX(3)(+) (where R = C6H11, X = CH3 (3); R = C6H11, X = C2H5 (4); R = p-CH3C6H4, X = CH3 (5) and R = p-CH3C6H4, X = C2H5 (6). The catalytic activity of both Cu-C2DTC and Cu-C6DTC was enhanced 35-70 % by 3-6 for concentrations of the host equivalent to the IC50 value of the complex. A correlation was found between the net positive charge of the nitrogen atom and the maximum acceleration attained by both complexes. The formation of an inclusion complex between these cationic guests and the CD moiety of these complexes is proposed to be the determining factor in the observed increase in the catalytic activity.