Cationic Hypericin Derivatives as Novel Agents with Photobactericidal Activity: Synthesis and Photodynamic Inactivation of Propionibacterium acnes

ABSTRACT

The present communication describes for the first time the synthesis and preliminary testing of two cationic hypericin derivatives. Uncharged hypericin derivatives with ω,ω'-attached C₂-linkers leading to a pyridyl or a 4-dimethylaminophenyl residue were prepared and subsequently quaternized by means of iodomethane. Photobactericidal activity was assessed using Propionibacterium acnes. The quaternary N,N,N-trimethyl-anilinium derivative displayed a pronounced photodynamic inactivation of the bacteria at low incubation concentrations (<100 nm) and a short incubation time (1 h) after illumination with yellow light (590 nm, 20 J cm⁻²), whereas the photobactericidal efficacy of the N-methyl-pyridinium derivative was negligible under identical experimental conditions.