5-Hydroxyisoquinolinium salts; Synthesis; Antimicrobial activity; Lipophilicity; Isoquinolinium salts

In the present paper, we describe the synthesis of a new group of 5-hydroxyisoquinolinium salts with different lengths of alkyl side-chain (C-10-C-18), and their chromatographic analysis and biological assay for in vitro activity against bacterial and fungal strains. We compare the lipophilicity and efficacy of hydroxylated isoquinolinium salts with the previously published (non-hydroxylated) isoquinolinium salts from the point of view of antibacterial and antifungal versatility and cytotoxic safety. Compound 11 (C-18) had to be excluded from the testing due to its low solubility. Compounds 9 and 10 (C-14, C-16) showed only moderate efficacy against G+ bacteria, notably with excellent potency against Staphyloccocus aureus, but no effect against G- bacteria. In contrast, non-hydroxylated isoquinolinium salts showed excellent antimicrobial efficacy within the whole series, particularly 14 (C-14) against G+ strains and 15 (C-16) against fungi.