The study was aimed to determine the ability of selected antibiotics and synthetic chemotherapeutic agents to interact with ascorbic acid by means of spectrophotometric measurements and the evaluation of the effect of the presence of ascorbic acid on antimicrobial activity of the substances in which the interaction was detected. Out of 13 chemotherapeutical agents tested, ofloxacine, N-succinimidylofloxacine, fleroxacine, tetracycline, 6-thiatetracycline, and doxycycline reacted with ascorbic acid with the development of the superoxide radical (O2 .- ). Heatley’s method revealed that in the presence of ascorbic acid the antibacterial effect of substances was decreased by 9.6 to 40.7 % and 10.1 to 45.1 % in Staphylococcus aureus and Escherichia coli, respectively. The kinetics of the process of the survival of cells within 24 hours demonstrated that a combination of ofloxacine as well as tetracycline with ascorbic acid produced a statistically significant increase in log 10 of CFU/ml in S. aureus as well as E. coli.

        Key words: ascorbic acid – antibiotics – synthetic chemotherapeutic agents – antibacterial