Pyomelanin, produced by the genus Pseudomonas, exhibits biological and pharmacological activity. The increased resistance to antimicrobial agents has made it necessary to search for new treatments that consider the interaction between biometals, natural pigments, and antibiotics such as ceftazidime. The present study examines the ability of natural pyomelanin and ceftazidime to complex copper(II) in parent and heteroligand systems in aqueous solutions. The results were characterized by UV-Vis spectrophotometry and confirmed by pH-metric testing. The formation constants were calculated for ceftazidime alone and for its CuLH+ complex with a protonated amide group in the ligand. In the case of natural melanin, our studies suggest the presence of quinone, catechol, and possible carboxyl groups that may be involved in the apparent binding of Cu(II) ions. Copper(II) was found to bind more effectively to ceftazidime than to natural pyomelanin; in addition, the presence of pyomelanin appeared to delay the hydrolysis of ceftazidime.
Woźniczka et al. (Mon,) studied this question.