Menthol modified zinc(II) phthalocyanine regioisomers and their photoinduced antimicrobial activity against Staphylococcus aureus

Our study is the first to investigate the antimicrobial activity of the single regioisomers rather than the mixture of isomeric phthalocyanines - regioisomers with symmetry C4, C1 and C2, functionalized with L-menthol in the periphery were obtained. The single Zn(II) phthalocyanine regioisomers were synthesized by remetallation reaction from the metal-free phthalocyanines. The obtained compounds were characterised using NMR, UV–Vis, IR spectroscopy and mass spectrometry. The analysed macrocycles generate singlet oxygen with the quantum yield up to 0.78. Menthol substituted three regioisomers of zinc(II) phthalocyanine were loaded into liposomes and subjected to biological activity study. The investigated compounds present low – C4 and moderate – C1 and C2 activity against Staphylococcus aureus. The highest bacterial growth inhibition (2.48 log) showed regioisomer C2 at the concentration of 10 μM.