Plasmid curing and antibacterial effects of some chlorpromazine derivatives in relation to their molecule orbitals

7-Hydroxychlorpromazine, 7,8-dihydroxychlorpromazine and 7,8-dioxochlorpromazine exerted a bacteriostatic effect on Gram-positive and Gram-negative bacteria, with the latter being more resistant. The three compounds also had a bactericidal effect on selected strains of Escherichia coli and Staphylococcus aureus. 7-Hydroxychlorpromazine was able to cure 2% of F'lac plasmid of the E. coli K-12 LE 140 strain at 60 micrograms/ml, while 7,8-dihydroxychlorpromazine and its quinone failed to produced such an effect at the same concentration. In the presence of 0.1 M magnesium sulphate the plasmid curing effect of CPZ and 7-OH-CPZ decreased markedly, while the MIC values of CPZ and its derivatives increased. It seems therefore that the relative ineffectivity of CPZ in the presence of magnesium ions was not due to its metal chelation.