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

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 n m ) 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.