Three new complexes of platinum(II) with doxycycline, oxytetracycline and chlortetracycline and their antimicrobial activity

This paper reports on the synthesis and characterization of three new platinum(II) complexes with oxytetracycline, doxycycline and chlortetracycline by elemental analysis, IR and Pt-195 RMN spectroscopies. Doxycycline interactions with PtII ions as a function of the pH were studied by H-1 NMR. All the investigated tetracyclines form 1:1 complexes with PtII via the oxygen of the hydroxyl group and oxygen of the amide group at ring A. The minimal inhibitory concentrations (MIC) of the ligands and those of their PtII compounds were determined in two sensitive strains (E. coli HB 101 and E. coli ATCC 25922) and in a resistant one (E. coli HB101/pBR322). Platinum complex of doxycycline is twice as potent as the free antibiotic in the resistant strain. Octanol/water partition coefficients of the complexes were determined. Increasing lipophilicity enhances antimicrobial activity in the resistant strain.