Antimicrobial and KPC/AmpC inhibitory activity of functionalized benzosiloxaboroles

Abstract A series of 22 benzosiloxaboroles, silicon analogues of strong antimicrobial agents - benzoxaboroles, have been synthesized and tested against β-lactamases KPC- and pAmpC-producing strains of Gram-negative rods. Comprehensive structural-property relationship studies supported by molecular modelling as well as biological studies reveal that 6-B(OH) 2 -substituted derivative 27 strongly inhibits the activity of cephalosporinases (chromosomally encoded AmpC and plasmid encoded CMY-2) and KPC carbapenemases. It also shows strong ability to inhibit growth of the strains producing KPC-3 when combined with meropenem. In addition, halogen-substituted (mono-, di- or tetra-) benzosiloxaboroles demonstrate high antifungal activity (MIC 1.56–6.25 mg/L) against C. tropicalis , C. guilliermondii and S. cerevisiae . The highest activity against pathogenic yeasts ( C. albicans , C. krusei and C. parapsilosis - MICs 12.5 mg/L) and against Gram-positive cocci ( S. aureus and E. faecalis - 6.25 mg/L and 25 mg/L respectively) was displayed by 6,7-dichloro-substituted benzosiloxaborole. The studied systems exhibit low cytotoxity toward human lung fibroblasts.