The question being posed by scientists around the world is how different chemical modifications of naturally occurring compounds will affect their antimicrobial properties. In the current study, sulfur derivatives of camphor containing a sulfur atom were tested to detect their antimicrobial and antibiofilm potentials. The new compounds were tested on eight Gram-positive strains (S. aureus (3 isolates), S. epidermidis (4 isolates), and E. faecalis (1 isolate)) and eight Gram-negative strains (E. coli (6 isolates), A. baumannii (1 isolate), and P. aeruginosa (1 isolate)). The ability of the strains to eradicate a biofilm was evaluated under standard stationary and flow-through conditions using the Bioflux system. Two synthesized compounds, namely rac-thiocamphor (1a) and (S, S)-(+)-thiocamphor (2a), exhibited an effect on the 24 h biofilm formed by the Gram-positive strains. Our results are an important contribution to the science of natural compounds and allow us to classify our sulfur derivatives of camphor as potential prophylactic agents in treating skin infections, antiseptics, and disinfectants. The Gram-negative strains were excluded from further stages of the tests due to their high activity (MIC ≥ 512 µg/mL). On the other hand, the compound with the strongest antimicrobial activity against the Gram-positive strains was 2a, as it led led to a reductions in cell viability of 17-52% (for MIC), 37-66% (for 2MIC), and 40-94% (for 4MIC). In addition, the experimental retention index of thiocamphor was calculated for the first time.
Keywords: antibiofilm activity; antimicrobial activity; camphor; monoterpenoids; skin infections; sulfur derivatives.